]> granicus.if.org Git - postgresql/blobdiff - src/backend/postmaster/pgstat.c
Avoid counting transaction stats for parallel worker cooperating
[postgresql] / src / backend / postmaster / pgstat.c
index 3ab1428f7c72cb3dc4a66c83c7ae97f8981f7498..7c0b24a16fa6b15dcae035677ea2e9ec3154f84e 100644 (file)
@@ -11,7 +11,7 @@
  *                     - Add a pgstat config column to pg_database, so this
  *                       entire thing can be enabled/disabled on a per db basis.
  *
- *     Copyright (c) 2001-2014, PostgreSQL Global Development Group
+ *     Copyright (c) 2001-2019, PostgreSQL Global Development Group
  *
  *     src/backend/postmaster/pgstat.c
  * ----------
 #include <arpa/inet.h>
 #include <signal.h>
 #include <time.h>
+#ifdef HAVE_SYS_SELECT_H
+#include <sys/select.h>
+#endif
 
 #include "pgstat.h"
 
 #include "access/heapam.h"
 #include "access/htup_details.h"
+#include "access/tableam.h"
 #include "access/transam.h"
 #include "access/twophase_rmgr.h"
 #include "access/xact.h"
 #include "catalog/pg_database.h"
 #include "catalog/pg_proc.h"
-#include "lib/ilist.h"
-#include "libpq/ip.h"
+#include "common/ip.h"
 #include "libpq/libpq.h"
 #include "libpq/pqsignal.h"
 #include "mb/pg_wchar.h"
 #include "postmaster/autovacuum.h"
 #include "postmaster/fork_process.h"
 #include "postmaster/postmaster.h"
-#include "storage/proc.h"
+#include "replication/walsender.h"
 #include "storage/backendid.h"
 #include "storage/dsm.h"
 #include "storage/fd.h"
 #include "storage/ipc.h"
 #include "storage/latch.h"
+#include "storage/lmgr.h"
 #include "storage/pg_shmem.h"
 #include "storage/procsignal.h"
 #include "storage/sinvaladt.h"
 #include "utils/rel.h"
 #include "utils/snapmgr.h"
 #include "utils/timestamp.h"
-#include "utils/tqual.h"
 
 
 /* ----------
  * Timer definitions.
  * ----------
  */
-#define PGSTAT_STAT_INTERVAL   500             /* Minimum time between stats file
-                                                                                * updates; in milliseconds. */
+#define PGSTAT_STAT_INTERVAL   500 /* Minimum time between stats file
+                                                                        * updates; in milliseconds. */
 
-#define PGSTAT_RETRY_DELAY             10              /* How long to wait between checks for
-                                                                                * a new file; in milliseconds. */
+#define PGSTAT_RETRY_DELAY             10      /* How long to wait between checks for a
+                                                                        * new file; in milliseconds. */
 
 #define PGSTAT_MAX_WAIT_TIME   10000   /* Maximum time to wait for a stats
                                                                                 * file update; in milliseconds. */
 
-#define PGSTAT_INQ_INTERVAL            640             /* How often to ping the collector for
-                                                                                * a new file; in milliseconds. */
+#define PGSTAT_INQ_INTERVAL            640 /* How often to ping the collector for a
+                                                                        * new file; in milliseconds. */
 
-#define PGSTAT_RESTART_INTERVAL 60             /* How often to attempt to restart a
-                                                                                * failed statistics collector; in
-                                                                                * seconds. */
+#define PGSTAT_RESTART_INTERVAL 60     /* How often to attempt to restart a
+                                                                        * failed statistics collector; in
+                                                                        * seconds. */
 
 #define PGSTAT_POLL_LOOP_COUNT (PGSTAT_MAX_WAIT_TIME / PGSTAT_RETRY_DELAY)
 #define PGSTAT_INQ_LOOP_COUNT  (PGSTAT_INQ_INTERVAL / PGSTAT_RETRY_DELAY)
 
+/* Minimum receive buffer size for the collector's socket. */
+#define PGSTAT_MIN_RCVBUF              (100 * 1024)
+
 
 /* ----------
  * The initial size hints for the hash tables used in the collector.
 #define PGSTAT_FUNCTION_HASH_SIZE      512
 
 
+/* ----------
+ * Total number of backends including auxiliary
+ *
+ * We reserve a slot for each possible BackendId, plus one for each
+ * possible auxiliary process type.  (This scheme assumes there is not
+ * more than one of any auxiliary process type at a time.) MaxBackends
+ * includes autovacuum workers and background workers as well.
+ * ----------
+ */
+#define NumBackendStatSlots (MaxBackends + NUM_AUXPROCTYPES)
+
+
 /* ----------
  * GUC parameters
  * ----------
@@ -130,8 +148,6 @@ PgStat_MsgBgWriter BgWriterStats;
  */
 NON_EXEC_STATIC pgsocket pgStatSock = PGINVALID_SOCKET;
 
-static Latch pgStatLatch;
-
 static struct sockaddr_storage pgStatAddr;
 
 static time_t last_pgstat_start_time;
@@ -160,6 +176,20 @@ typedef struct TabStatusArray
 
 static TabStatusArray *pgStatTabList = NULL;
 
+/*
+ * pgStatTabHash entry: map from relation OID to PgStat_TableStatus pointer
+ */
+typedef struct TabStatHashEntry
+{
+       Oid                     t_id;
+       PgStat_TableStatus *tsa_entry;
+} TabStatHashEntry;
+
+/*
+ * Hash table for O(1) t_id -> tsa_entry lookup
+ */
+static HTAB *pgStatTabHash = NULL;
+
 /*
  * Backends store per-function info that's waiting to be sent to the collector
  * in this hash table (indexed by function OID).
@@ -183,7 +213,7 @@ typedef struct PgStat_SubXactStatus
 {
        int                     nest_level;             /* subtransaction nest level */
        struct PgStat_SubXactStatus *prev;      /* higher-level subxact if any */
-       PgStat_TableXactStatus *first;          /* head of list for this subxact */
+       PgStat_TableXactStatus *first;  /* head of list for this subxact */
 } PgStat_SubXactStatus;
 
 static PgStat_SubXactStatus *pgStatXactStack = NULL;
@@ -196,11 +226,15 @@ PgStat_Counter pgStatBlockWriteTime = 0;
 /* Record that's written to 2PC state file when pgstat state is persisted */
 typedef struct TwoPhasePgStatRecord
 {
-       PgStat_Counter tuples_inserted;         /* tuples inserted in xact */
-       PgStat_Counter tuples_updated;          /* tuples updated in xact */
-       PgStat_Counter tuples_deleted;          /* tuples deleted in xact */
+       PgStat_Counter tuples_inserted; /* tuples inserted in xact */
+       PgStat_Counter tuples_updated;  /* tuples updated in xact */
+       PgStat_Counter tuples_deleted;  /* tuples deleted in xact */
+       PgStat_Counter inserted_pre_trunc;      /* tuples inserted prior to truncate */
+       PgStat_Counter updated_pre_trunc;       /* tuples updated prior to truncate */
+       PgStat_Counter deleted_pre_trunc;       /* tuples deleted prior to truncate */
        Oid                     t_id;                   /* table's OID */
        bool            t_shared;               /* is it a shared catalog? */
+       bool            t_truncated;    /* was the relation truncated? */
 } TwoPhasePgStatRecord;
 
 /*
@@ -208,7 +242,11 @@ typedef struct TwoPhasePgStatRecord
  */
 static MemoryContext pgStatLocalContext = NULL;
 static HTAB *pgStatDBHash = NULL;
+
+/* Status for backends including auxiliary */
 static LocalPgBackendStatus *localBackendStatusTable = NULL;
+
+/* Total number of backends including auxiliary */
 static int     localNumBackends = 0;
 
 /*
@@ -219,17 +257,14 @@ static int        localNumBackends = 0;
 static PgStat_ArchiverStats archiverStats;
 static PgStat_GlobalStats globalStats;
 
-/* Write request info for each database */
-typedef struct DBWriteRequest
-{
-       Oid                     databaseid;             /* OID of the database to write */
-       TimestampTz request_time;       /* timestamp of the last write request */
-       slist_node      next;
-} DBWriteRequest;
-
-/* Latest statistics request times from backends */
-static slist_head last_statrequests = SLIST_STATIC_INIT(last_statrequests);
+/*
+ * List of OIDs of databases we need to write out.  If an entry is InvalidOid,
+ * it means to write only the shared-catalog stats ("DB 0"); otherwise, we
+ * will write both that DB's data and the shared stats.
+ */
+static List *pending_write_requests = NIL;
 
+/* Signal handler flags */
 static volatile bool need_exit = false;
 static volatile bool got_SIGHUP = false;
 
@@ -249,7 +284,7 @@ static instr_time total_func_time;
 static pid_t pgstat_forkexec(void);
 #endif
 
-NON_EXEC_STATIC void PgstatCollectorMain(int argc, char *argv[]) __attribute__((noreturn));
+NON_EXEC_STATIC void PgstatCollectorMain(int argc, char *argv[]) pg_attribute_noreturn();
 static void pgstat_exit(SIGNAL_ARGS);
 static void pgstat_beshutdown_hook(int code, Datum arg);
 static void pgstat_sighup_handler(SIGNAL_ARGS);
@@ -269,12 +304,18 @@ static bool pgstat_db_requested(Oid databaseid);
 
 static void pgstat_send_tabstat(PgStat_MsgTabstat *tsmsg);
 static void pgstat_send_funcstats(void);
-static HTAB *pgstat_collect_oids(Oid catalogid);
+static HTAB *pgstat_collect_oids(Oid catalogid, AttrNumber anum_oid);
 
 static PgStat_TableStatus *get_tabstat_entry(Oid rel_id, bool isshared);
 
 static void pgstat_setup_memcxt(void);
 
+static const char *pgstat_get_wait_activity(WaitEventActivity w);
+static const char *pgstat_get_wait_client(WaitEventClient w);
+static const char *pgstat_get_wait_ipc(WaitEventIPC w);
+static const char *pgstat_get_wait_timeout(WaitEventTimeout w);
+static const char *pgstat_get_wait_io(WaitEventIO w);
+
 static void pgstat_setheader(PgStat_MsgHdr *hdr, StatMsgType mtype);
 static void pgstat_send(void *msg, int len);
 
@@ -294,6 +335,7 @@ static void pgstat_recv_funcstat(PgStat_MsgFuncstat *msg, int len);
 static void pgstat_recv_funcpurge(PgStat_MsgFuncpurge *msg, int len);
 static void pgstat_recv_recoveryconflict(PgStat_MsgRecoveryConflict *msg, int len);
 static void pgstat_recv_deadlock(PgStat_MsgDeadlock *msg, int len);
+static void pgstat_recv_checksum_failure(PgStat_MsgChecksumFailure *msg, int len);
 static void pgstat_recv_tempfile(PgStat_MsgTempFile *msg, int len);
 
 /* ------------------------------------------------------------
@@ -334,7 +376,7 @@ pgstat_init(void)
         * compile-time cross-check that we didn't.
         */
        StaticAssertStmt(sizeof(PgStat_Msg) <= PGSTAT_MAX_MSG_SIZE,
-                                  "maximum stats message size exceeds PGSTAT_MAX_MSG_SIZE");
+                                        "maximum stats message size exceeds PGSTAT_MAX_MSG_SIZE");
 
        /*
         * Create the UDP socket for sending and receiving statistic messages
@@ -374,7 +416,7 @@ pgstat_init(void)
 
                if (++tries > 1)
                        ereport(LOG,
-                       (errmsg("trying another address for the statistics collector")));
+                                       (errmsg("trying another address for the statistics collector")));
 
                /*
                 * Create the socket.
@@ -383,7 +425,7 @@ pgstat_init(void)
                {
                        ereport(LOG,
                                        (errcode_for_socket_access(),
-                       errmsg("could not create socket for statistics collector: %m")));
+                                        errmsg("could not create socket for statistics collector: %m")));
                        continue;
                }
 
@@ -395,14 +437,14 @@ pgstat_init(void)
                {
                        ereport(LOG,
                                        (errcode_for_socket_access(),
-                         errmsg("could not bind socket for statistics collector: %m")));
+                                        errmsg("could not bind socket for statistics collector: %m")));
                        closesocket(pgStatSock);
                        pgStatSock = PGINVALID_SOCKET;
                        continue;
                }
 
                alen = sizeof(pgStatAddr);
-               if (getsockname(pgStatSock, (struct sockaddr *) & pgStatAddr, &alen) < 0)
+               if (getsockname(pgStatSock, (struct sockaddr *) &pgStatAddr, &alen) < 0)
                {
                        ereport(LOG,
                                        (errcode_for_socket_access(),
@@ -418,11 +460,11 @@ pgstat_init(void)
                 * provides a kernel-level check that only packets from this same
                 * address will be received.
                 */
-               if (connect(pgStatSock, (struct sockaddr *) & pgStatAddr, alen) < 0)
+               if (connect(pgStatSock, (struct sockaddr *) &pgStatAddr, alen) < 0)
                {
                        ereport(LOG,
                                        (errcode_for_socket_access(),
-                       errmsg("could not connect socket for statistics collector: %m")));
+                                        errmsg("could not connect socket for statistics collector: %m")));
                        closesocket(pgStatSock);
                        pgStatSock = PGINVALID_SOCKET;
                        continue;
@@ -536,13 +578,42 @@ retry2:
                goto startup_failed;
        }
 
+       /*
+        * Try to ensure that the socket's receive buffer is at least
+        * PGSTAT_MIN_RCVBUF bytes, so that it won't easily overflow and lose
+        * data.  Use of UDP protocol means that we are willing to lose data under
+        * heavy load, but we don't want it to happen just because of ridiculously
+        * small default buffer sizes (such as 8KB on older Windows versions).
+        */
+       {
+               int                     old_rcvbuf;
+               int                     new_rcvbuf;
+               ACCEPT_TYPE_ARG3 rcvbufsize = sizeof(old_rcvbuf);
+
+               if (getsockopt(pgStatSock, SOL_SOCKET, SO_RCVBUF,
+                                          (char *) &old_rcvbuf, &rcvbufsize) < 0)
+               {
+                       elog(LOG, "getsockopt(SO_RCVBUF) failed: %m");
+                       /* if we can't get existing size, always try to set it */
+                       old_rcvbuf = 0;
+               }
+
+               new_rcvbuf = PGSTAT_MIN_RCVBUF;
+               if (old_rcvbuf < new_rcvbuf)
+               {
+                       if (setsockopt(pgStatSock, SOL_SOCKET, SO_RCVBUF,
+                                                  (char *) &new_rcvbuf, sizeof(new_rcvbuf)) < 0)
+                               elog(LOG, "setsockopt(SO_RCVBUF) failed: %m");
+               }
+       }
+
        pg_freeaddrinfo_all(hints.ai_family, addrs);
 
        return;
 
 startup_failed:
        ereport(LOG,
-         (errmsg("disabling statistics collector for lack of working socket")));
+                       (errmsg("disabling statistics collector for lack of working socket")));
 
        if (addrs)
                pg_freeaddrinfo_all(hints.ai_family, addrs);
@@ -568,7 +639,7 @@ pgstat_reset_remove_files(const char *directory)
 {
        DIR                *dir;
        struct dirent *entry;
-       char            fname[MAXPGPATH];
+       char            fname[MAXPGPATH * 2];
 
        dir = AllocateDir(directory);
        while ((entry = ReadDir(dir, directory)) != NULL)
@@ -598,7 +669,7 @@ pgstat_reset_remove_files(const char *directory)
                        strcmp(entry->d_name + nchars, "stat") != 0)
                        continue;
 
-               snprintf(fname, MAXPGPATH, "%s/%s", directory,
+               snprintf(fname, sizeof(fname), "%s/%s", directory,
                                 entry->d_name);
                unlink(fname);
        }
@@ -640,7 +711,7 @@ pgstat_forkexec(void)
 
        return postmaster_forkexec(ac, av);
 }
-#endif   /* EXEC_BACKEND */
+#endif                                                 /* EXEC_BACKEND */
 
 
 /*
@@ -695,12 +766,11 @@ pgstat_start(void)
 #ifndef EXEC_BACKEND
                case 0:
                        /* in postmaster child ... */
+                       InitPostmasterChild();
+
                        /* Close the postmaster's sockets */
                        ClosePostmasterPorts(false);
 
-                       /* Lose the postmaster's on-exit routines */
-                       on_exit_reset();
-
                        /* Drop our connection to postmaster's shared memory, as well */
                        dsm_detach_all();
                        PGSharedMemoryDetach();
@@ -732,9 +802,10 @@ allow_immediate_pgstat_restart(void)
 /* ----------
  * pgstat_report_stat() -
  *
- *     Called from tcop/postgres.c to send the so far collected per-table
- *     and function usage statistics to the collector.  Note that this is
- *     called only when not within a transaction, so it is fair to use
+ *     Must be called by processes that performs DML: tcop/postgres.c, logical
+ *     receiver processes, SPI worker, etc. to send the so far collected
+ *     per-table and function usage statistics to the collector.  Note that this
+ *     is called only when not within a transaction, so it is fair to use
  *     transaction stop time as an approximation of current time.
  * ----------
  */
@@ -753,7 +824,8 @@ pgstat_report_stat(bool force)
 
        /* Don't expend a clock check if nothing to do */
        if ((pgStatTabList == NULL || pgStatTabList->tsa_used == 0) &&
-               !have_function_stats && !force)
+               pgStatXactCommit == 0 && pgStatXactRollback == 0 &&
+               !have_function_stats)
                return;
 
        /*
@@ -766,6 +838,17 @@ pgstat_report_stat(bool force)
                return;
        last_report = now;
 
+       /*
+        * Destroy pgStatTabHash before we start invalidating PgStat_TableEntry
+        * entries it points to.  (Should we fail partway through the loop below,
+        * it's okay to have removed the hashtable already --- the only
+        * consequence is we'd get multiple entries for the same table in the
+        * pgStatTabList, and that's safe.)
+        */
+       if (pgStatTabHash)
+               hash_destroy(pgStatTabHash);
+       pgStatTabHash = NULL;
+
        /*
         * Scan through the TabStatusArray struct(s) to find tables that actually
         * have counts, and build messages to send.  We have to separate shared
@@ -817,11 +900,11 @@ pgstat_report_stat(bool force)
        }
 
        /*
-        * Send partial messages.  If force is true, make sure that any pending
-        * xact commit/abort gets counted, even if no table stats to send.
+        * Send partial messages.  Make sure that any pending xact commit/abort
+        * gets counted, even if there are no table stats to send.
         */
        if (regular_msg.m_nentries > 0 ||
-               (force && (pgStatXactCommit > 0 || pgStatXactRollback > 0)))
+               pgStatXactCommit > 0 || pgStatXactRollback > 0)
                pgstat_send_tabstat(&regular_msg);
        if (shared_msg.m_nentries > 0)
                pgstat_send_tabstat(&shared_msg);
@@ -960,7 +1043,7 @@ pgstat_vacuum_stat(void)
        /*
         * Read pg_database and make a list of OIDs of all existing databases
         */
-       htab = pgstat_collect_oids(DatabaseRelationId);
+       htab = pgstat_collect_oids(DatabaseRelationId, Anum_pg_database_oid);
 
        /*
         * Search the database hash table for dead databases and tell the
@@ -994,7 +1077,7 @@ pgstat_vacuum_stat(void)
        /*
         * Similarly to above, make a list of all known relations in this DB.
         */
-       htab = pgstat_collect_oids(RelationRelationId);
+       htab = pgstat_collect_oids(RelationRelationId, Anum_pg_class_oid);
 
        /*
         * Initialize our messages table counter to zero
@@ -1025,7 +1108,7 @@ pgstat_vacuum_stat(void)
                if (msg.m_nentries >= PGSTAT_NUM_TABPURGE)
                {
                        len = offsetof(PgStat_MsgTabpurge, m_tableid[0])
-                               +msg.m_nentries * sizeof(Oid);
+                               + msg.m_nentries * sizeof(Oid);
 
                        pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_TABPURGE);
                        msg.m_databaseid = MyDatabaseId;
@@ -1041,7 +1124,7 @@ pgstat_vacuum_stat(void)
        if (msg.m_nentries > 0)
        {
                len = offsetof(PgStat_MsgTabpurge, m_tableid[0])
-                       +msg.m_nentries * sizeof(Oid);
+                       + msg.m_nentries * sizeof(Oid);
 
                pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_TABPURGE);
                msg.m_databaseid = MyDatabaseId;
@@ -1058,7 +1141,7 @@ pgstat_vacuum_stat(void)
        if (dbentry->functions != NULL &&
                hash_get_num_entries(dbentry->functions) > 0)
        {
-               htab = pgstat_collect_oids(ProcedureRelationId);
+               htab = pgstat_collect_oids(ProcedureRelationId, Anum_pg_proc_oid);
 
                pgstat_setheader(&f_msg.m_hdr, PGSTAT_MTYPE_FUNCPURGE);
                f_msg.m_databaseid = MyDatabaseId;
@@ -1085,7 +1168,7 @@ pgstat_vacuum_stat(void)
                        if (f_msg.m_nentries >= PGSTAT_NUM_FUNCPURGE)
                        {
                                len = offsetof(PgStat_MsgFuncpurge, m_functionid[0])
-                                       +f_msg.m_nentries * sizeof(Oid);
+                                       + f_msg.m_nentries * sizeof(Oid);
 
                                pgstat_send(&f_msg, len);
 
@@ -1099,7 +1182,7 @@ pgstat_vacuum_stat(void)
                if (f_msg.m_nentries > 0)
                {
                        len = offsetof(PgStat_MsgFuncpurge, m_functionid[0])
-                               +f_msg.m_nentries * sizeof(Oid);
+                               + f_msg.m_nentries * sizeof(Oid);
 
                        pgstat_send(&f_msg, len);
                }
@@ -1119,39 +1202,42 @@ pgstat_vacuum_stat(void)
  * ----------
  */
 static HTAB *
-pgstat_collect_oids(Oid catalogid)
+pgstat_collect_oids(Oid catalogid, AttrNumber anum_oid)
 {
        HTAB       *htab;
        HASHCTL         hash_ctl;
        Relation        rel;
-       HeapScanDesc scan;
+       TableScanDesc scan;
        HeapTuple       tup;
        Snapshot        snapshot;
 
        memset(&hash_ctl, 0, sizeof(hash_ctl));
        hash_ctl.keysize = sizeof(Oid);
        hash_ctl.entrysize = sizeof(Oid);
-       hash_ctl.hash = oid_hash;
        hash_ctl.hcxt = CurrentMemoryContext;
        htab = hash_create("Temporary table of OIDs",
                                           PGSTAT_TAB_HASH_SIZE,
                                           &hash_ctl,
-                                          HASH_ELEM | HASH_FUNCTION | HASH_CONTEXT);
+                                          HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
 
-       rel = heap_open(catalogid, AccessShareLock);
+       rel = table_open(catalogid, AccessShareLock);
        snapshot = RegisterSnapshot(GetLatestSnapshot());
-       scan = heap_beginscan(rel, snapshot, 0, NULL);
+       scan = table_beginscan(rel, snapshot, 0, NULL);
        while ((tup = heap_getnext(scan, ForwardScanDirection)) != NULL)
        {
-               Oid                     thisoid = HeapTupleGetOid(tup);
+               Oid                     thisoid;
+               bool            isnull;
+
+               thisoid = heap_getattr(tup, anum_oid, RelationGetDescr(rel), &isnull);
+               Assert(!isnull);
 
                CHECK_FOR_INTERRUPTS();
 
                (void) hash_search(htab, (void *) &thisoid, HASH_ENTER, NULL);
        }
-       heap_endscan(scan);
+       table_endscan(scan);
        UnregisterSnapshot(snapshot);
-       heap_close(rel, AccessShareLock);
+       table_close(rel, AccessShareLock);
 
        return htab;
 }
@@ -1203,19 +1289,22 @@ pgstat_drop_relation(Oid relid)
        msg.m_tableid[0] = relid;
        msg.m_nentries = 1;
 
-       len = offsetof(PgStat_MsgTabpurge, m_tableid[0]) +sizeof(Oid);
+       len = offsetof(PgStat_MsgTabpurge, m_tableid[0]) + sizeof(Oid);
 
        pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_TABPURGE);
        msg.m_databaseid = MyDatabaseId;
        pgstat_send(&msg, len);
 }
-#endif   /* NOT_USED */
+#endif                                                 /* NOT_USED */
 
 
 /* ----------
  * pgstat_reset_counters() -
  *
  *     Tell the statistics collector to reset counters for our database.
+ *
+ *     Permission checking for this function is managed through the normal
+ *     GRANT system.
  * ----------
  */
 void
@@ -1226,11 +1315,6 @@ pgstat_reset_counters(void)
        if (pgStatSock == PGINVALID_SOCKET)
                return;
 
-       if (!superuser())
-               ereport(ERROR,
-                               (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-                                errmsg("must be superuser to reset statistics counters")));
-
        pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_RESETCOUNTER);
        msg.m_databaseid = MyDatabaseId;
        pgstat_send(&msg, sizeof(msg));
@@ -1240,6 +1324,9 @@ pgstat_reset_counters(void)
  * pgstat_reset_shared_counters() -
  *
  *     Tell the statistics collector to reset cluster-wide shared counters.
+ *
+ *     Permission checking for this function is managed through the normal
+ *     GRANT system.
  * ----------
  */
 void
@@ -1250,11 +1337,6 @@ pgstat_reset_shared_counters(const char *target)
        if (pgStatSock == PGINVALID_SOCKET)
                return;
 
-       if (!superuser())
-               ereport(ERROR,
-                               (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-                                errmsg("must be superuser to reset statistics counters")));
-
        if (strcmp(target, "archiver") == 0)
                msg.m_resettarget = RESET_ARCHIVER;
        else if (strcmp(target, "bgwriter") == 0)
@@ -1273,6 +1355,9 @@ pgstat_reset_shared_counters(const char *target)
  * pgstat_reset_single_counter() -
  *
  *     Tell the statistics collector to reset a single counter.
+ *
+ *     Permission checking for this function is managed through the normal
+ *     GRANT system.
  * ----------
  */
 void
@@ -1283,11 +1368,6 @@ pgstat_reset_single_counter(Oid objoid, PgStat_Single_Reset_Type type)
        if (pgStatSock == PGINVALID_SOCKET)
                return;
 
-       if (!superuser())
-               ereport(ERROR,
-                               (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-                                errmsg("must be superuser to reset statistics counters")));
-
        pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_RESETSINGLECOUNTER);
        msg.m_databaseid = MyDatabaseId;
        msg.m_resettype = type;
@@ -1349,11 +1429,15 @@ pgstat_report_vacuum(Oid tableoid, bool shared,
  * pgstat_report_analyze() -
  *
  *     Tell the collector about the table we just analyzed.
+ *
+ * Caller must provide new live- and dead-tuples estimates, as well as a
+ * flag indicating whether to reset the changes_since_analyze counter.
  * --------
  */
 void
 pgstat_report_analyze(Relation rel,
-                                         PgStat_Counter livetuples, PgStat_Counter deadtuples)
+                                         PgStat_Counter livetuples, PgStat_Counter deadtuples,
+                                         bool resetcounter)
 {
        PgStat_MsgAnalyze msg;
 
@@ -1390,6 +1474,7 @@ pgstat_report_analyze(Relation rel,
        msg.m_databaseid = rel->rd_rel->relisshared ? InvalidOid : MyDatabaseId;
        msg.m_tableoid = RelationGetRelid(rel);
        msg.m_autovacuum = IsAutoVacuumWorkerProcess();
+       msg.m_resetcounter = resetcounter;
        msg.m_analyzetime = GetCurrentTimestamp();
        msg.m_live_tuples = livetuples;
        msg.m_dead_tuples = deadtuples;
@@ -1435,6 +1520,40 @@ pgstat_report_deadlock(void)
        pgstat_send(&msg, sizeof(msg));
 }
 
+
+
+/* --------
+ * pgstat_report_checksum_failures_in_db(dboid, failure_count) -
+ *
+ *     Tell the collector about one or more checksum failures.
+ * --------
+ */
+void
+pgstat_report_checksum_failures_in_db(Oid dboid, int failurecount)
+{
+       PgStat_MsgChecksumFailure msg;
+
+       if (pgStatSock == PGINVALID_SOCKET || !pgstat_track_counts)
+               return;
+
+       pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_CHECKSUMFAILURE);
+       msg.m_databaseid = dboid;
+       msg.m_failurecount = failurecount;
+       pgstat_send(&msg, sizeof(msg));
+}
+
+/* --------
+ * pgstat_report_checksum_failure() -
+ *
+ *     Tell the collector about a checksum failure.
+ * --------
+ */
+void
+pgstat_report_checksum_failure(void)
+{
+       pgstat_report_checksum_failures_in_db(MyDatabaseId, 1);
+}
+
 /* --------
  * pgstat_report_tempfile() -
  *
@@ -1498,7 +1617,7 @@ pgstat_send_inquiry(TimestampTz clock_time, TimestampTz cutoff_time, Oid databas
  * Called by the executor before invoking a function.
  */
 void
-pgstat_init_function_usage(FunctionCallInfoData *fcinfo,
+pgstat_init_function_usage(FunctionCallInfo fcinfo,
                                                   PgStat_FunctionCallUsage *fcu)
 {
        PgStat_BackendFunctionEntry *htabent;
@@ -1519,11 +1638,10 @@ pgstat_init_function_usage(FunctionCallInfoData *fcinfo,
                memset(&hash_ctl, 0, sizeof(hash_ctl));
                hash_ctl.keysize = sizeof(Oid);
                hash_ctl.entrysize = sizeof(PgStat_BackendFunctionEntry);
-               hash_ctl.hash = oid_hash;
                pgStatFunctions = hash_create("Function stat entries",
                                                                          PGSTAT_FUNCTION_HASH_SIZE,
                                                                          &hash_ctl,
-                                                                         HASH_ELEM | HASH_FUNCTION);
+                                                                         HASH_ELEM | HASH_BLOBS);
        }
 
        /* Get the stats entry for this function, create if necessary */
@@ -1669,54 +1787,80 @@ pgstat_initstats(Relation rel)
 static PgStat_TableStatus *
 get_tabstat_entry(Oid rel_id, bool isshared)
 {
+       TabStatHashEntry *hash_entry;
        PgStat_TableStatus *entry;
        TabStatusArray *tsa;
-       TabStatusArray *prev_tsa;
-       int                     i;
+       bool            found;
 
        /*
-        * Search the already-used tabstat slots for this relation.
+        * Create hash table if we don't have it already.
         */
-       prev_tsa = NULL;
-       for (tsa = pgStatTabList; tsa != NULL; prev_tsa = tsa, tsa = tsa->tsa_next)
+       if (pgStatTabHash == NULL)
        {
-               for (i = 0; i < tsa->tsa_used; i++)
-               {
-                       entry = &tsa->tsa_entries[i];
-                       if (entry->t_id == rel_id)
-                               return entry;
-               }
+               HASHCTL         ctl;
 
-               if (tsa->tsa_used < TABSTAT_QUANTUM)
-               {
-                       /*
-                        * It must not be present, but we found a free slot instead. Fine,
-                        * let's use this one.  We assume the entry was already zeroed,
-                        * either at creation or after last use.
-                        */
-                       entry = &tsa->tsa_entries[tsa->tsa_used++];
-                       entry->t_id = rel_id;
-                       entry->t_shared = isshared;
-                       return entry;
-               }
+               memset(&ctl, 0, sizeof(ctl));
+               ctl.keysize = sizeof(Oid);
+               ctl.entrysize = sizeof(TabStatHashEntry);
+
+               pgStatTabHash = hash_create("pgstat TabStatusArray lookup hash table",
+                                                                       TABSTAT_QUANTUM,
+                                                                       &ctl,
+                                                                       HASH_ELEM | HASH_BLOBS);
        }
 
        /*
-        * We ran out of tabstat slots, so allocate more.  Be sure they're zeroed.
+        * Find an entry or create a new one.
         */
-       tsa = (TabStatusArray *) MemoryContextAllocZero(TopMemoryContext,
-                                                                                                       sizeof(TabStatusArray));
-       if (prev_tsa)
-               prev_tsa->tsa_next = tsa;
-       else
-               pgStatTabList = tsa;
+       hash_entry = hash_search(pgStatTabHash, &rel_id, HASH_ENTER, &found);
+       if (!found)
+       {
+               /* initialize new entry with null pointer */
+               hash_entry->tsa_entry = NULL;
+       }
+
+       /*
+        * If entry is already valid, we're done.
+        */
+       if (hash_entry->tsa_entry)
+               return hash_entry->tsa_entry;
+
+       /*
+        * Locate the first pgStatTabList entry with free space, making a new list
+        * entry if needed.  Note that we could get an OOM failure here, but if so
+        * we have left the hashtable and the list in a consistent state.
+        */
+       if (pgStatTabList == NULL)
+       {
+               /* Set up first pgStatTabList entry */
+               pgStatTabList = (TabStatusArray *)
+                       MemoryContextAllocZero(TopMemoryContext,
+                                                                  sizeof(TabStatusArray));
+       }
+
+       tsa = pgStatTabList;
+       while (tsa->tsa_used >= TABSTAT_QUANTUM)
+       {
+               if (tsa->tsa_next == NULL)
+                       tsa->tsa_next = (TabStatusArray *)
+                               MemoryContextAllocZero(TopMemoryContext,
+                                                                          sizeof(TabStatusArray));
+               tsa = tsa->tsa_next;
+       }
 
        /*
-        * Use the first entry of the new TabStatusArray.
+        * Allocate a PgStat_TableStatus entry within this list entry.  We assume
+        * the entry was already zeroed, either at creation or after last use.
         */
        entry = &tsa->tsa_entries[tsa->tsa_used++];
        entry->t_id = rel_id;
        entry->t_shared = isshared;
+
+       /*
+        * Now we can fill the entry in pgStatTabHash.
+        */
+       hash_entry->tsa_entry = entry;
+
        return entry;
 }
 
@@ -1724,26 +1868,26 @@ get_tabstat_entry(Oid rel_id, bool isshared)
  * find_tabstat_entry - find any existing PgStat_TableStatus entry for rel
  *
  * If no entry, return NULL, don't create a new one
+ *
+ * Note: if we got an error in the most recent execution of pgstat_report_stat,
+ * it's possible that an entry exists but there's no hashtable entry for it.
+ * That's okay, we'll treat this case as "doesn't exist".
  */
 PgStat_TableStatus *
 find_tabstat_entry(Oid rel_id)
 {
-       PgStat_TableStatus *entry;
-       TabStatusArray *tsa;
-       int                     i;
+       TabStatHashEntry *hash_entry;
 
-       for (tsa = pgStatTabList; tsa != NULL; tsa = tsa->tsa_next)
-       {
-               for (i = 0; i < tsa->tsa_used; i++)
-               {
-                       entry = &tsa->tsa_entries[i];
-                       if (entry->t_id == rel_id)
-                               return entry;
-               }
-       }
+       /* If hashtable doesn't exist, there are no entries at all */
+       if (!pgStatTabHash)
+               return NULL;
 
-       /* Not present */
-       return NULL;
+       hash_entry = hash_search(pgStatTabHash, &rel_id, HASH_FIND, NULL);
+       if (!hash_entry)
+               return NULL;
+
+       /* Note that this step could also return NULL, but that's correct */
+       return hash_entry->tsa_entry;
 }
 
 /*
@@ -1799,7 +1943,7 @@ add_tabstat_xact_level(PgStat_TableStatus *pgstat_info, int nest_level)
  * pgstat_count_heap_insert - count a tuple insertion of n tuples
  */
 void
-pgstat_count_heap_insert(Relation rel, int n)
+pgstat_count_heap_insert(Relation rel, PgStat_Counter n)
 {
        PgStat_TableStatus *pgstat_info = rel->pgstat_info;
 
@@ -1862,6 +2006,64 @@ pgstat_count_heap_delete(Relation rel)
        }
 }
 
+/*
+ * pgstat_truncate_save_counters
+ *
+ * Whenever a table is truncated, we save its i/u/d counters so that they can
+ * be cleared, and if the (sub)xact that executed the truncate later aborts,
+ * the counters can be restored to the saved (pre-truncate) values.  Note we do
+ * this on the first truncate in any particular subxact level only.
+ */
+static void
+pgstat_truncate_save_counters(PgStat_TableXactStatus *trans)
+{
+       if (!trans->truncated)
+       {
+               trans->inserted_pre_trunc = trans->tuples_inserted;
+               trans->updated_pre_trunc = trans->tuples_updated;
+               trans->deleted_pre_trunc = trans->tuples_deleted;
+               trans->truncated = true;
+       }
+}
+
+/*
+ * pgstat_truncate_restore_counters - restore counters when a truncate aborts
+ */
+static void
+pgstat_truncate_restore_counters(PgStat_TableXactStatus *trans)
+{
+       if (trans->truncated)
+       {
+               trans->tuples_inserted = trans->inserted_pre_trunc;
+               trans->tuples_updated = trans->updated_pre_trunc;
+               trans->tuples_deleted = trans->deleted_pre_trunc;
+       }
+}
+
+/*
+ * pgstat_count_truncate - update tuple counters due to truncate
+ */
+void
+pgstat_count_truncate(Relation rel)
+{
+       PgStat_TableStatus *pgstat_info = rel->pgstat_info;
+
+       if (pgstat_info != NULL)
+       {
+               /* We have to log the effect at the proper transactional level */
+               int                     nest_level = GetCurrentTransactionNestLevel();
+
+               if (pgstat_info->trans == NULL ||
+                       pgstat_info->trans->nest_level != nest_level)
+                       add_tabstat_xact_level(pgstat_info, nest_level);
+
+               pgstat_truncate_save_counters(pgstat_info->trans);
+               pgstat_info->trans->tuples_inserted = 0;
+               pgstat_info->trans->tuples_updated = 0;
+               pgstat_info->trans->tuples_deleted = 0;
+       }
+}
+
 /*
  * pgstat_update_heap_dead_tuples - update dead-tuples count
  *
@@ -1887,18 +2089,22 @@ pgstat_update_heap_dead_tuples(Relation rel, int delta)
  * ----------
  */
 void
-AtEOXact_PgStat(bool isCommit)
+AtEOXact_PgStat(bool isCommit, bool parallel)
 {
        PgStat_SubXactStatus *xact_state;
 
-       /*
-        * Count transaction commit or abort.  (We use counters, not just bools,
-        * in case the reporting message isn't sent right away.)
-        */
-       if (isCommit)
-               pgStatXactCommit++;
-       else
-               pgStatXactRollback++;
+       /* Don't count parallel worker transaction stats */
+       if (!parallel)
+       {
+               /*
+                * Count transaction commit or abort.  (We use counters, not just
+                * bools, in case the reporting message isn't sent right away.)
+                */
+               if (isCommit)
+                       pgStatXactCommit++;
+               else
+                       pgStatXactRollback++;
+       }
 
        /*
         * Transfer transactional insert/update counts into the base tabstat
@@ -1920,12 +2126,22 @@ AtEOXact_PgStat(bool isCommit)
                        Assert(trans->upper == NULL);
                        tabstat = trans->parent;
                        Assert(tabstat->trans == trans);
+                       /* restore pre-truncate stats (if any) in case of aborted xact */
+                       if (!isCommit)
+                               pgstat_truncate_restore_counters(trans);
                        /* count attempted actions regardless of commit/abort */
                        tabstat->t_counts.t_tuples_inserted += trans->tuples_inserted;
                        tabstat->t_counts.t_tuples_updated += trans->tuples_updated;
                        tabstat->t_counts.t_tuples_deleted += trans->tuples_deleted;
                        if (isCommit)
                        {
+                               tabstat->t_counts.t_truncated = trans->truncated;
+                               if (trans->truncated)
+                               {
+                                       /* forget live/dead stats seen by backend thus far */
+                                       tabstat->t_counts.t_delta_live_tuples = 0;
+                                       tabstat->t_counts.t_delta_dead_tuples = 0;
+                               }
                                /* insert adds a live tuple, delete removes one */
                                tabstat->t_counts.t_delta_live_tuples +=
                                        trans->tuples_inserted - trans->tuples_deleted;
@@ -1990,9 +2206,21 @@ AtEOSubXact_PgStat(bool isCommit, int nestDepth)
                        {
                                if (trans->upper && trans->upper->nest_level == nestDepth - 1)
                                {
-                                       trans->upper->tuples_inserted += trans->tuples_inserted;
-                                       trans->upper->tuples_updated += trans->tuples_updated;
-                                       trans->upper->tuples_deleted += trans->tuples_deleted;
+                                       if (trans->truncated)
+                                       {
+                                               /* propagate the truncate status one level up */
+                                               pgstat_truncate_save_counters(trans->upper);
+                                               /* replace upper xact stats with ours */
+                                               trans->upper->tuples_inserted = trans->tuples_inserted;
+                                               trans->upper->tuples_updated = trans->tuples_updated;
+                                               trans->upper->tuples_deleted = trans->tuples_deleted;
+                                       }
+                                       else
+                                       {
+                                               trans->upper->tuples_inserted += trans->tuples_inserted;
+                                               trans->upper->tuples_updated += trans->tuples_updated;
+                                               trans->upper->tuples_deleted += trans->tuples_deleted;
+                                       }
                                        tabstat->trans = trans->upper;
                                        pfree(trans);
                                }
@@ -2021,6 +2249,8 @@ AtEOSubXact_PgStat(bool isCommit, int nestDepth)
                                 * subtransaction
                                 */
 
+                               /* first restore values obliterated by truncate */
+                               pgstat_truncate_restore_counters(trans);
                                /* count attempted actions regardless of commit/abort */
                                tabstat->t_counts.t_tuples_inserted += trans->tuples_inserted;
                                tabstat->t_counts.t_tuples_updated += trans->tuples_updated;
@@ -2069,8 +2299,12 @@ AtPrepare_PgStat(void)
                        record.tuples_inserted = trans->tuples_inserted;
                        record.tuples_updated = trans->tuples_updated;
                        record.tuples_deleted = trans->tuples_deleted;
+                       record.inserted_pre_trunc = trans->inserted_pre_trunc;
+                       record.updated_pre_trunc = trans->updated_pre_trunc;
+                       record.deleted_pre_trunc = trans->deleted_pre_trunc;
                        record.t_id = tabstat->t_id;
                        record.t_shared = tabstat->t_shared;
+                       record.t_truncated = trans->truncated;
 
                        RegisterTwoPhaseRecord(TWOPHASE_RM_PGSTAT_ID, 0,
                                                                   &record, sizeof(TwoPhasePgStatRecord));
@@ -2136,6 +2370,13 @@ pgstat_twophase_postcommit(TransactionId xid, uint16 info,
        pgstat_info->t_counts.t_tuples_inserted += rec->tuples_inserted;
        pgstat_info->t_counts.t_tuples_updated += rec->tuples_updated;
        pgstat_info->t_counts.t_tuples_deleted += rec->tuples_deleted;
+       pgstat_info->t_counts.t_truncated = rec->t_truncated;
+       if (rec->t_truncated)
+       {
+               /* forget live/dead stats seen by backend thus far */
+               pgstat_info->t_counts.t_delta_live_tuples = 0;
+               pgstat_info->t_counts.t_delta_dead_tuples = 0;
+       }
        pgstat_info->t_counts.t_delta_live_tuples +=
                rec->tuples_inserted - rec->tuples_deleted;
        pgstat_info->t_counts.t_delta_dead_tuples +=
@@ -2162,6 +2403,12 @@ pgstat_twophase_postabort(TransactionId xid, uint16 info,
        pgstat_info = get_tabstat_entry(rec->t_id, rec->t_shared);
 
        /* Same math as in AtEOXact_PgStat, abort case */
+       if (rec->t_truncated)
+       {
+               rec->tuples_inserted = rec->inserted_pre_trunc;
+               rec->tuples_updated = rec->updated_pre_trunc;
+               rec->tuples_deleted = rec->deleted_pre_trunc;
+       }
        pgstat_info->t_counts.t_tuples_inserted += rec->tuples_inserted;
        pgstat_info->t_counts.t_tuples_updated += rec->tuples_updated;
        pgstat_info->t_counts.t_tuples_deleted += rec->tuples_deleted;
@@ -2309,7 +2556,7 @@ pgstat_fetch_stat_beentry(int beid)
 /* ----------
  * pgstat_fetch_stat_local_beentry() -
  *
- *     Like pgstat_fetch_stat_beentry() but with locally computed addtions (like
+ *     Like pgstat_fetch_stat_beentry() but with locally computed additions (like
  *     xid and xmin values of the backend)
  *
  *     NB: caller is responsible for a check if the user is permitted to see
@@ -2384,10 +2631,16 @@ pgstat_fetch_global(void)
 
 static PgBackendStatus *BackendStatusArray = NULL;
 static PgBackendStatus *MyBEEntry = NULL;
-static char *BackendClientHostnameBuffer = NULL;
 static char *BackendAppnameBuffer = NULL;
+static char *BackendClientHostnameBuffer = NULL;
 static char *BackendActivityBuffer = NULL;
 static Size BackendActivityBufferSize = 0;
+#ifdef USE_SSL
+static PgBackendSSLStatus *BackendSslStatusBuffer = NULL;
+#endif
+#ifdef ENABLE_GSS
+static PgBackendGSSStatus *BackendGssStatusBuffer = NULL;
+#endif
 
 
 /*
@@ -2398,13 +2651,22 @@ BackendStatusShmemSize(void)
 {
        Size            size;
 
-       size = mul_size(sizeof(PgBackendStatus), MaxBackends);
+       /* BackendStatusArray: */
+       size = mul_size(sizeof(PgBackendStatus), NumBackendStatSlots);
+       /* BackendAppnameBuffer: */
        size = add_size(size,
-                                       mul_size(NAMEDATALEN, MaxBackends));
+                                       mul_size(NAMEDATALEN, NumBackendStatSlots));
+       /* BackendClientHostnameBuffer: */
        size = add_size(size,
-                                       mul_size(pgstat_track_activity_query_size, MaxBackends));
+                                       mul_size(NAMEDATALEN, NumBackendStatSlots));
+       /* BackendActivityBuffer: */
        size = add_size(size,
-                                       mul_size(NAMEDATALEN, MaxBackends));
+                                       mul_size(pgstat_track_activity_query_size, NumBackendStatSlots));
+#ifdef USE_SSL
+       /* BackendSslStatusBuffer: */
+       size = add_size(size,
+                                       mul_size(sizeof(PgBackendSSLStatus), NumBackendStatSlots));
+#endif
        return size;
 }
 
@@ -2421,7 +2683,7 @@ CreateSharedBackendStatus(void)
        char       *buffer;
 
        /* Create or attach to the shared array */
-       size = mul_size(sizeof(PgBackendStatus), MaxBackends);
+       size = mul_size(sizeof(PgBackendStatus), NumBackendStatSlots);
        BackendStatusArray = (PgBackendStatus *)
                ShmemInitStruct("Backend Status Array", size, &found);
 
@@ -2434,7 +2696,7 @@ CreateSharedBackendStatus(void)
        }
 
        /* Create or attach to the shared appname buffer */
-       size = mul_size(NAMEDATALEN, MaxBackends);
+       size = mul_size(NAMEDATALEN, NumBackendStatSlots);
        BackendAppnameBuffer = (char *)
                ShmemInitStruct("Backend Application Name Buffer", size, &found);
 
@@ -2444,7 +2706,7 @@ CreateSharedBackendStatus(void)
 
                /* Initialize st_appname pointers. */
                buffer = BackendAppnameBuffer;
-               for (i = 0; i < MaxBackends; i++)
+               for (i = 0; i < NumBackendStatSlots; i++)
                {
                        BackendStatusArray[i].st_appname = buffer;
                        buffer += NAMEDATALEN;
@@ -2452,7 +2714,7 @@ CreateSharedBackendStatus(void)
        }
 
        /* Create or attach to the shared client hostname buffer */
-       size = mul_size(NAMEDATALEN, MaxBackends);
+       size = mul_size(NAMEDATALEN, NumBackendStatSlots);
        BackendClientHostnameBuffer = (char *)
                ShmemInitStruct("Backend Client Host Name Buffer", size, &found);
 
@@ -2462,7 +2724,7 @@ CreateSharedBackendStatus(void)
 
                /* Initialize st_clienthostname pointers. */
                buffer = BackendClientHostnameBuffer;
-               for (i = 0; i < MaxBackends; i++)
+               for (i = 0; i < NumBackendStatSlots; i++)
                {
                        BackendStatusArray[i].st_clienthostname = buffer;
                        buffer += NAMEDATALEN;
@@ -2471,7 +2733,7 @@ CreateSharedBackendStatus(void)
 
        /* Create or attach to the shared activity buffer */
        BackendActivityBufferSize = mul_size(pgstat_track_activity_query_size,
-                                                                                MaxBackends);
+                                                                                NumBackendStatSlots);
        BackendActivityBuffer = (char *)
                ShmemInitStruct("Backend Activity Buffer",
                                                BackendActivityBufferSize,
@@ -2479,16 +2741,60 @@ CreateSharedBackendStatus(void)
 
        if (!found)
        {
-               MemSet(BackendActivityBuffer, 0, size);
+               MemSet(BackendActivityBuffer, 0, BackendActivityBufferSize);
 
                /* Initialize st_activity pointers. */
                buffer = BackendActivityBuffer;
-               for (i = 0; i < MaxBackends; i++)
+               for (i = 0; i < NumBackendStatSlots; i++)
                {
-                       BackendStatusArray[i].st_activity = buffer;
+                       BackendStatusArray[i].st_activity_raw = buffer;
                        buffer += pgstat_track_activity_query_size;
                }
        }
+
+#ifdef USE_SSL
+       /* Create or attach to the shared SSL status buffer */
+       size = mul_size(sizeof(PgBackendSSLStatus), NumBackendStatSlots);
+       BackendSslStatusBuffer = (PgBackendSSLStatus *)
+               ShmemInitStruct("Backend SSL Status Buffer", size, &found);
+
+       if (!found)
+       {
+               PgBackendSSLStatus *ptr;
+
+               MemSet(BackendSslStatusBuffer, 0, size);
+
+               /* Initialize st_sslstatus pointers. */
+               ptr = BackendSslStatusBuffer;
+               for (i = 0; i < NumBackendStatSlots; i++)
+               {
+                       BackendStatusArray[i].st_sslstatus = ptr;
+                       ptr++;
+               }
+       }
+#endif
+
+#ifdef ENABLE_GSS
+       /* Create or attach to the shared GSSAPI status buffer */
+       size = mul_size(sizeof(PgBackendGSSStatus), NumBackendStatSlots);
+       BackendGssStatusBuffer = (PgBackendGSSStatus *)
+               ShmemInitStruct("Backend GSS Status Buffer", size, &found);
+
+       if (!found)
+       {
+               PgBackendGSSStatus *ptr;
+
+               MemSet(BackendGssStatusBuffer, 0, size);
+
+               /* Initialize st_gssstatus pointers. */
+               ptr = BackendGssStatusBuffer;
+               for (i = 0; i < NumBackendStatSlots; i++)
+               {
+                       BackendStatusArray[i].st_gssstatus = ptr;
+                       ptr++;
+               }
+       }
+#endif
 }
 
 
@@ -2496,7 +2802,8 @@ CreateSharedBackendStatus(void)
  * pgstat_initialize() -
  *
  *     Initialize pgstats state, and set up our on-proc-exit hook.
- *     Called from InitPostgres.  MyBackendId must be set,
+ *     Called from InitPostgres and AuxiliaryProcessMain. For auxiliary process,
+ *     MyBackendId is invalid. Otherwise, MyBackendId must be set,
  *     but we must not have started any transaction yet (since the
  *     exit hook must run after the last transaction exit).
  *     NOTE: MyDatabaseId isn't set yet; so the shutdown hook has to be careful.
@@ -2506,8 +2813,26 @@ void
 pgstat_initialize(void)
 {
        /* Initialize MyBEEntry */
-       Assert(MyBackendId >= 1 && MyBackendId <= MaxBackends);
-       MyBEEntry = &BackendStatusArray[MyBackendId - 1];
+       if (MyBackendId != InvalidBackendId)
+       {
+               Assert(MyBackendId >= 1 && MyBackendId <= MaxBackends);
+               MyBEEntry = &BackendStatusArray[MyBackendId - 1];
+       }
+       else
+       {
+               /* Must be an auxiliary process */
+               Assert(MyAuxProcType != NotAnAuxProcess);
+
+               /*
+                * Assign the MyBEEntry for an auxiliary process.  Since it doesn't
+                * have a BackendId, the slot is statically allocated based on the
+                * auxiliary process type (MyAuxProcType).  Backends use slots indexed
+                * in the range from 1 to MaxBackends (inclusive), so we use
+                * MaxBackends + AuxBackendType + 1 as the index of the slot for an
+                * auxiliary process.
+                */
+               MyBEEntry = &BackendStatusArray[MaxBackends + MyAuxProcType];
+       }
 
        /* Set up a process-exit hook to clean up */
        on_shmem_exit(pgstat_beshutdown_hook, 0);
@@ -2518,30 +2843,22 @@ pgstat_initialize(void)
  *
  *     Initialize this backend's entry in the PgBackendStatus array.
  *     Called from InitPostgres.
- *     MyDatabaseId, session userid, and application_name must be set
- *     (hence, this cannot be combined with pgstat_initialize).
+ *
+ *     Apart from auxiliary processes, MyBackendId, MyDatabaseId,
+ *     session userid, and application_name must be set for a
+ *     backend (hence, this cannot be combined with pgstat_initialize).
  * ----------
  */
 void
 pgstat_bestart(void)
 {
-       TimestampTz proc_start_timestamp;
-       Oid                     userid;
        SockAddr        clientaddr;
        volatile PgBackendStatus *beentry;
 
        /*
         * To minimize the time spent modifying the PgBackendStatus entry, fetch
         * all the needed data first.
-        *
-        * If we have a MyProcPort, use its session start time (for consistency,
-        * and to save a kernel call).
         */
-       if (MyProcPort)
-               proc_start_timestamp = MyProcPort->SessionStartTime;
-       else
-               proc_start_timestamp = GetCurrentTimestamp();
-       userid = GetSessionUserId();
 
        /*
         * We may not have a MyProcPort (eg, if this is the autovacuum process).
@@ -2560,35 +2877,146 @@ pgstat_bestart(void)
         * cute.
         */
        beentry = MyBEEntry;
+
+       /* pgstats state must be initialized from pgstat_initialize() */
+       Assert(beentry != NULL);
+
+       if (MyBackendId != InvalidBackendId)
+       {
+               if (IsAutoVacuumLauncherProcess())
+               {
+                       /* Autovacuum Launcher */
+                       beentry->st_backendType = B_AUTOVAC_LAUNCHER;
+               }
+               else if (IsAutoVacuumWorkerProcess())
+               {
+                       /* Autovacuum Worker */
+                       beentry->st_backendType = B_AUTOVAC_WORKER;
+               }
+               else if (am_walsender)
+               {
+                       /* Wal sender */
+                       beentry->st_backendType = B_WAL_SENDER;
+               }
+               else if (IsBackgroundWorker)
+               {
+                       /* bgworker */
+                       beentry->st_backendType = B_BG_WORKER;
+               }
+               else
+               {
+                       /* client-backend */
+                       beentry->st_backendType = B_BACKEND;
+               }
+       }
+       else
+       {
+               /* Must be an auxiliary process */
+               Assert(MyAuxProcType != NotAnAuxProcess);
+               switch (MyAuxProcType)
+               {
+                       case StartupProcess:
+                               beentry->st_backendType = B_STARTUP;
+                               break;
+                       case BgWriterProcess:
+                               beentry->st_backendType = B_BG_WRITER;
+                               break;
+                       case CheckpointerProcess:
+                               beentry->st_backendType = B_CHECKPOINTER;
+                               break;
+                       case WalWriterProcess:
+                               beentry->st_backendType = B_WAL_WRITER;
+                               break;
+                       case WalReceiverProcess:
+                               beentry->st_backendType = B_WAL_RECEIVER;
+                               break;
+                       default:
+                               elog(FATAL, "unrecognized process type: %d",
+                                        (int) MyAuxProcType);
+                               proc_exit(1);
+               }
+       }
+
        do
        {
-               beentry->st_changecount++;
+               pgstat_increment_changecount_before(beentry);
        } while ((beentry->st_changecount & 1) == 0);
 
        beentry->st_procpid = MyProcPid;
-       beentry->st_proc_start_timestamp = proc_start_timestamp;
+       beentry->st_proc_start_timestamp = MyStartTimestamp;
        beentry->st_activity_start_timestamp = 0;
        beentry->st_state_start_timestamp = 0;
        beentry->st_xact_start_timestamp = 0;
        beentry->st_databaseid = MyDatabaseId;
-       beentry->st_userid = userid;
+
+       /* We have userid for client-backends, wal-sender and bgworker processes */
+       if (beentry->st_backendType == B_BACKEND
+               || beentry->st_backendType == B_WAL_SENDER
+               || beentry->st_backendType == B_BG_WORKER)
+               beentry->st_userid = GetSessionUserId();
+       else
+               beentry->st_userid = InvalidOid;
+
        beentry->st_clientaddr = clientaddr;
        if (MyProcPort && MyProcPort->remote_hostname)
                strlcpy(beentry->st_clienthostname, MyProcPort->remote_hostname,
                                NAMEDATALEN);
        else
                beentry->st_clienthostname[0] = '\0';
-       beentry->st_waiting = false;
+#ifdef USE_SSL
+       if (MyProcPort && MyProcPort->ssl != NULL)
+       {
+               beentry->st_ssl = true;
+               beentry->st_sslstatus->ssl_bits = be_tls_get_cipher_bits(MyProcPort);
+               beentry->st_sslstatus->ssl_compression = be_tls_get_compression(MyProcPort);
+               strlcpy(beentry->st_sslstatus->ssl_version, be_tls_get_version(MyProcPort), NAMEDATALEN);
+               strlcpy(beentry->st_sslstatus->ssl_cipher, be_tls_get_cipher(MyProcPort), NAMEDATALEN);
+               be_tls_get_peer_subject_name(MyProcPort, beentry->st_sslstatus->ssl_client_dn, NAMEDATALEN);
+               be_tls_get_peer_serial(MyProcPort, beentry->st_sslstatus->ssl_client_serial, NAMEDATALEN);
+               be_tls_get_peer_issuer_name(MyProcPort, beentry->st_sslstatus->ssl_issuer_dn, NAMEDATALEN);
+       }
+       else
+       {
+               beentry->st_ssl = false;
+       }
+#else
+       beentry->st_ssl = false;
+#endif
+
+#ifdef ENABLE_GSS
+       if (MyProcPort && MyProcPort->gss != NULL)
+       {
+               beentry->st_gss = true;
+               beentry->st_gssstatus->gss_auth = be_gssapi_get_auth(MyProcPort);
+               beentry->st_gssstatus->gss_enc = be_gssapi_get_enc(MyProcPort);
+
+               if (beentry->st_gssstatus->gss_auth)
+                       strlcpy(beentry->st_gssstatus->gss_princ, be_gssapi_get_princ(MyProcPort), NAMEDATALEN);
+       }
+       else
+       {
+               beentry->st_gss = false;
+       }
+#else
+       beentry->st_gss = false;
+#endif
        beentry->st_state = STATE_UNDEFINED;
        beentry->st_appname[0] = '\0';
-       beentry->st_activity[0] = '\0';
+       beentry->st_activity_raw[0] = '\0';
        /* Also make sure the last byte in each string area is always 0 */
        beentry->st_clienthostname[NAMEDATALEN - 1] = '\0';
        beentry->st_appname[NAMEDATALEN - 1] = '\0';
-       beentry->st_activity[pgstat_track_activity_query_size - 1] = '\0';
+       beentry->st_activity_raw[pgstat_track_activity_query_size - 1] = '\0';
+       beentry->st_progress_command = PROGRESS_COMMAND_INVALID;
+       beentry->st_progress_command_target = InvalidOid;
+
+       /*
+        * we don't zero st_progress_param here to save cycles; nobody should
+        * examine it until st_progress_command has been set to something other
+        * than PROGRESS_COMMAND_INVALID
+        */
 
-       beentry->st_changecount++;
-       Assert((beentry->st_changecount & 1) == 0);
+       pgstat_increment_changecount_after(beentry);
 
        /* Update app name to current GUC setting */
        if (application_name)
@@ -2623,12 +3051,11 @@ pgstat_beshutdown_hook(int code, Datum arg)
         * before and after.  We use a volatile pointer here to ensure the
         * compiler doesn't try to get cute.
         */
-       beentry->st_changecount++;
+       pgstat_increment_changecount_before(beentry);
 
        beentry->st_procpid = 0;        /* mark invalid */
 
-       beentry->st_changecount++;
-       Assert((beentry->st_changecount & 1) == 0);
+       pgstat_increment_changecount_after(beentry);
 }
 
 
@@ -2660,21 +3087,22 @@ pgstat_report_activity(BackendState state, const char *cmd_str)
        {
                if (beentry->st_state != STATE_DISABLED)
                {
+                       volatile PGPROC *proc = MyProc;
+
                        /*
                         * track_activities is disabled, but we last reported a
                         * non-disabled state.  As our final update, change the state and
                         * clear fields we will not be updating anymore.
                         */
-                       beentry->st_changecount++;
+                       pgstat_increment_changecount_before(beentry);
                        beentry->st_state = STATE_DISABLED;
                        beentry->st_state_start_timestamp = 0;
-                       beentry->st_activity[0] = '\0';
+                       beentry->st_activity_raw[0] = '\0';
                        beentry->st_activity_start_timestamp = 0;
-                       /* st_xact_start_timestamp and st_waiting are also disabled */
+                       /* st_xact_start_timestamp and wait_event_info are also disabled */
                        beentry->st_xact_start_timestamp = 0;
-                       beentry->st_waiting = false;
-                       beentry->st_changecount++;
-                       Assert((beentry->st_changecount & 1) == 0);
+                       proc->wait_event_info = 0;
+                       pgstat_increment_changecount_after(beentry);
                }
                return;
        }
@@ -2686,28 +3114,127 @@ pgstat_report_activity(BackendState state, const char *cmd_str)
        start_timestamp = GetCurrentStatementStartTimestamp();
        if (cmd_str != NULL)
        {
-               len = pg_mbcliplen(cmd_str, strlen(cmd_str),
-                                                  pgstat_track_activity_query_size - 1);
-       }
+               /*
+                * Compute length of to-be-stored string unaware of multi-byte
+                * characters. For speed reasons that'll get corrected on read, rather
+                * than computed every write.
+                */
+               len = Min(strlen(cmd_str), pgstat_track_activity_query_size - 1);
+       }
        current_timestamp = GetCurrentTimestamp();
 
        /*
         * Now update the status entry
         */
-       beentry->st_changecount++;
+       pgstat_increment_changecount_before(beentry);
 
        beentry->st_state = state;
        beentry->st_state_start_timestamp = current_timestamp;
 
        if (cmd_str != NULL)
        {
-               memcpy((char *) beentry->st_activity, cmd_str, len);
-               beentry->st_activity[len] = '\0';
+               memcpy((char *) beentry->st_activity_raw, cmd_str, len);
+               beentry->st_activity_raw[len] = '\0';
                beentry->st_activity_start_timestamp = start_timestamp;
        }
 
-       beentry->st_changecount++;
-       Assert((beentry->st_changecount & 1) == 0);
+       pgstat_increment_changecount_after(beentry);
+}
+
+/*-----------
+ * pgstat_progress_start_command() -
+ *
+ * Set st_progress_command (and st_progress_command_target) in own backend
+ * entry.  Also, zero-initialize st_progress_param array.
+ *-----------
+ */
+void
+pgstat_progress_start_command(ProgressCommandType cmdtype, Oid relid)
+{
+       volatile PgBackendStatus *beentry = MyBEEntry;
+
+       if (!beentry || !pgstat_track_activities)
+               return;
+
+       pgstat_increment_changecount_before(beentry);
+       beentry->st_progress_command = cmdtype;
+       beentry->st_progress_command_target = relid;
+       MemSet(&beentry->st_progress_param, 0, sizeof(beentry->st_progress_param));
+       pgstat_increment_changecount_after(beentry);
+}
+
+/*-----------
+ * pgstat_progress_update_param() -
+ *
+ * Update index'th member in st_progress_param[] of own backend entry.
+ *-----------
+ */
+void
+pgstat_progress_update_param(int index, int64 val)
+{
+       volatile PgBackendStatus *beentry = MyBEEntry;
+
+       Assert(index >= 0 && index < PGSTAT_NUM_PROGRESS_PARAM);
+
+       if (!beentry || !pgstat_track_activities)
+               return;
+
+       pgstat_increment_changecount_before(beentry);
+       beentry->st_progress_param[index] = val;
+       pgstat_increment_changecount_after(beentry);
+}
+
+/*-----------
+ * pgstat_progress_update_multi_param() -
+ *
+ * Update multiple members in st_progress_param[] of own backend entry.
+ * This is atomic; readers won't see intermediate states.
+ *-----------
+ */
+void
+pgstat_progress_update_multi_param(int nparam, const int *index,
+                                                                  const int64 *val)
+{
+       volatile PgBackendStatus *beentry = MyBEEntry;
+       int                     i;
+
+       if (!beentry || !pgstat_track_activities || nparam == 0)
+               return;
+
+       pgstat_increment_changecount_before(beentry);
+
+       for (i = 0; i < nparam; ++i)
+       {
+               Assert(index[i] >= 0 && index[i] < PGSTAT_NUM_PROGRESS_PARAM);
+
+               beentry->st_progress_param[index[i]] = val[i];
+       }
+
+       pgstat_increment_changecount_after(beentry);
+}
+
+/*-----------
+ * pgstat_progress_end_command() -
+ *
+ * Reset st_progress_command (and st_progress_command_target) in own backend
+ * entry.  This signals the end of the command.
+ *-----------
+ */
+void
+pgstat_progress_end_command(void)
+{
+       volatile PgBackendStatus *beentry = MyBEEntry;
+
+       if (!beentry)
+               return;
+       if (!pgstat_track_activities
+               && beentry->st_progress_command == PROGRESS_COMMAND_INVALID)
+               return;
+
+       pgstat_increment_changecount_before(beentry);
+       beentry->st_progress_command = PROGRESS_COMMAND_INVALID;
+       beentry->st_progress_command_target = InvalidOid;
+       pgstat_increment_changecount_after(beentry);
 }
 
 /* ----------
@@ -2733,13 +3260,12 @@ pgstat_report_appname(const char *appname)
         * st_changecount before and after.  We use a volatile pointer here to
         * ensure the compiler doesn't try to get cute.
         */
-       beentry->st_changecount++;
+       pgstat_increment_changecount_before(beentry);
 
        memcpy((char *) beentry->st_appname, appname, len);
        beentry->st_appname[len] = '\0';
 
-       beentry->st_changecount++;
-       Assert((beentry->st_changecount & 1) == 0);
+       pgstat_increment_changecount_after(beentry);
 }
 
 /*
@@ -2759,38 +3285,11 @@ pgstat_report_xact_timestamp(TimestampTz tstamp)
         * st_changecount before and after.  We use a volatile pointer here to
         * ensure the compiler doesn't try to get cute.
         */
-       beentry->st_changecount++;
+       pgstat_increment_changecount_before(beentry);
        beentry->st_xact_start_timestamp = tstamp;
-       beentry->st_changecount++;
-       Assert((beentry->st_changecount & 1) == 0);
+       pgstat_increment_changecount_after(beentry);
 }
 
-/* ----------
- * pgstat_report_waiting() -
- *
- *     Called from lock manager to report beginning or end of a lock wait.
- *
- * NB: this *must* be able to survive being called before MyBEEntry has been
- * initialized.
- * ----------
- */
-void
-pgstat_report_waiting(bool waiting)
-{
-       volatile PgBackendStatus *beentry = MyBEEntry;
-
-       if (!pgstat_track_activities || !beentry)
-               return;
-
-       /*
-        * Since this is a single-byte field in a struct that only this process
-        * may modify, there seems no need to bother with the st_changecount
-        * protocol.  The update must appear atomic in any case.
-        */
-       beentry->st_waiting = waiting;
-}
-
-
 /* ----------
  * pgstat_read_current_status() -
  *
@@ -2805,7 +3304,11 @@ pgstat_read_current_status(void)
        LocalPgBackendStatus *localtable;
        LocalPgBackendStatus *localentry;
        char       *localappname,
+                          *localclienthostname,
                           *localactivity;
+#ifdef USE_SSL
+       PgBackendSSLStatus *localsslstatus;
+#endif
        int                     i;
 
        Assert(!pgStatRunningInCollector);
@@ -2816,18 +3319,27 @@ pgstat_read_current_status(void)
 
        localtable = (LocalPgBackendStatus *)
                MemoryContextAlloc(pgStatLocalContext,
-                                                  sizeof(LocalPgBackendStatus) * MaxBackends);
+                                                  sizeof(LocalPgBackendStatus) * NumBackendStatSlots);
        localappname = (char *)
                MemoryContextAlloc(pgStatLocalContext,
-                                                  NAMEDATALEN * MaxBackends);
+                                                  NAMEDATALEN * NumBackendStatSlots);
+       localclienthostname = (char *)
+               MemoryContextAlloc(pgStatLocalContext,
+                                                  NAMEDATALEN * NumBackendStatSlots);
        localactivity = (char *)
                MemoryContextAlloc(pgStatLocalContext,
-                                                  pgstat_track_activity_query_size * MaxBackends);
+                                                  pgstat_track_activity_query_size * NumBackendStatSlots);
+#ifdef USE_SSL
+       localsslstatus = (PgBackendSSLStatus *)
+               MemoryContextAlloc(pgStatLocalContext,
+                                                  sizeof(PgBackendSSLStatus) * NumBackendStatSlots);
+#endif
+
        localNumBackends = 0;
 
        beentry = BackendStatusArray;
        localentry = localtable;
-       for (i = 1; i <= MaxBackends; i++)
+       for (i = 1; i <= NumBackendStatSlots; i++)
        {
                /*
                 * Follow the protocol of retrying if st_changecount changes while we
@@ -2838,12 +3350,15 @@ pgstat_read_current_status(void)
                 */
                for (;;)
                {
-                       int                     save_changecount = beentry->st_changecount;
+                       int                     before_changecount;
+                       int                     after_changecount;
+
+                       pgstat_save_changecount_before(beentry, before_changecount);
 
                        localentry->backendStatus.st_procpid = beentry->st_procpid;
                        if (localentry->backendStatus.st_procpid > 0)
                        {
-                               memcpy(&localentry->backendStatus, (char *) beentry, sizeof(PgBackendStatus));
+                               memcpy(&localentry->backendStatus, unvolatize(PgBackendStatus *, beentry), sizeof(PgBackendStatus));
 
                                /*
                                 * strcpy is safe even if the string is modified concurrently,
@@ -2851,12 +3366,23 @@ pgstat_read_current_status(void)
                                 */
                                strcpy(localappname, (char *) beentry->st_appname);
                                localentry->backendStatus.st_appname = localappname;
-                               strcpy(localactivity, (char *) beentry->st_activity);
-                               localentry->backendStatus.st_activity = localactivity;
+                               strcpy(localclienthostname, (char *) beentry->st_clienthostname);
+                               localentry->backendStatus.st_clienthostname = localclienthostname;
+                               strcpy(localactivity, (char *) beentry->st_activity_raw);
+                               localentry->backendStatus.st_activity_raw = localactivity;
+                               localentry->backendStatus.st_ssl = beentry->st_ssl;
+#ifdef USE_SSL
+                               if (beentry->st_ssl)
+                               {
+                                       memcpy(localsslstatus, beentry->st_sslstatus, sizeof(PgBackendSSLStatus));
+                                       localentry->backendStatus.st_sslstatus = localsslstatus;
+                               }
+#endif
                        }
 
-                       if (save_changecount == beentry->st_changecount &&
-                               (save_changecount & 1) == 0)
+                       pgstat_save_changecount_after(beentry, after_changecount);
+                       if (before_changecount == after_changecount &&
+                               (before_changecount & 1) == 0)
                                break;
 
                        /* Make sure we can break out of loop if stuck... */
@@ -2873,7 +3399,11 @@ pgstat_read_current_status(void)
 
                        localentry++;
                        localappname += NAMEDATALEN;
+                       localclienthostname += NAMEDATALEN;
                        localactivity += pgstat_track_activity_query_size;
+#ifdef USE_SSL
+                       localsslstatus++;
+#endif
                        localNumBackends++;
                }
        }
@@ -2882,6 +3412,627 @@ pgstat_read_current_status(void)
        localBackendStatusTable = localtable;
 }
 
+/* ----------
+ * pgstat_get_wait_event_type() -
+ *
+ *     Return a string representing the current wait event type, backend is
+ *     waiting on.
+ */
+const char *
+pgstat_get_wait_event_type(uint32 wait_event_info)
+{
+       uint32          classId;
+       const char *event_type;
+
+       /* report process as not waiting. */
+       if (wait_event_info == 0)
+               return NULL;
+
+       classId = wait_event_info & 0xFF000000;
+
+       switch (classId)
+       {
+               case PG_WAIT_LWLOCK:
+                       event_type = "LWLock";
+                       break;
+               case PG_WAIT_LOCK:
+                       event_type = "Lock";
+                       break;
+               case PG_WAIT_BUFFER_PIN:
+                       event_type = "BufferPin";
+                       break;
+               case PG_WAIT_ACTIVITY:
+                       event_type = "Activity";
+                       break;
+               case PG_WAIT_CLIENT:
+                       event_type = "Client";
+                       break;
+               case PG_WAIT_EXTENSION:
+                       event_type = "Extension";
+                       break;
+               case PG_WAIT_IPC:
+                       event_type = "IPC";
+                       break;
+               case PG_WAIT_TIMEOUT:
+                       event_type = "Timeout";
+                       break;
+               case PG_WAIT_IO:
+                       event_type = "IO";
+                       break;
+               default:
+                       event_type = "???";
+                       break;
+       }
+
+       return event_type;
+}
+
+/* ----------
+ * pgstat_get_wait_event() -
+ *
+ *     Return a string representing the current wait event, backend is
+ *     waiting on.
+ */
+const char *
+pgstat_get_wait_event(uint32 wait_event_info)
+{
+       uint32          classId;
+       uint16          eventId;
+       const char *event_name;
+
+       /* report process as not waiting. */
+       if (wait_event_info == 0)
+               return NULL;
+
+       classId = wait_event_info & 0xFF000000;
+       eventId = wait_event_info & 0x0000FFFF;
+
+       switch (classId)
+       {
+               case PG_WAIT_LWLOCK:
+                       event_name = GetLWLockIdentifier(classId, eventId);
+                       break;
+               case PG_WAIT_LOCK:
+                       event_name = GetLockNameFromTagType(eventId);
+                       break;
+               case PG_WAIT_BUFFER_PIN:
+                       event_name = "BufferPin";
+                       break;
+               case PG_WAIT_ACTIVITY:
+                       {
+                               WaitEventActivity w = (WaitEventActivity) wait_event_info;
+
+                               event_name = pgstat_get_wait_activity(w);
+                               break;
+                       }
+               case PG_WAIT_CLIENT:
+                       {
+                               WaitEventClient w = (WaitEventClient) wait_event_info;
+
+                               event_name = pgstat_get_wait_client(w);
+                               break;
+                       }
+               case PG_WAIT_EXTENSION:
+                       event_name = "Extension";
+                       break;
+               case PG_WAIT_IPC:
+                       {
+                               WaitEventIPC w = (WaitEventIPC) wait_event_info;
+
+                               event_name = pgstat_get_wait_ipc(w);
+                               break;
+                       }
+               case PG_WAIT_TIMEOUT:
+                       {
+                               WaitEventTimeout w = (WaitEventTimeout) wait_event_info;
+
+                               event_name = pgstat_get_wait_timeout(w);
+                               break;
+                       }
+               case PG_WAIT_IO:
+                       {
+                               WaitEventIO w = (WaitEventIO) wait_event_info;
+
+                               event_name = pgstat_get_wait_io(w);
+                               break;
+                       }
+               default:
+                       event_name = "unknown wait event";
+                       break;
+       }
+
+       return event_name;
+}
+
+/* ----------
+ * pgstat_get_wait_activity() -
+ *
+ * Convert WaitEventActivity to string.
+ * ----------
+ */
+static const char *
+pgstat_get_wait_activity(WaitEventActivity w)
+{
+       const char *event_name = "unknown wait event";
+
+       switch (w)
+       {
+               case WAIT_EVENT_ARCHIVER_MAIN:
+                       event_name = "ArchiverMain";
+                       break;
+               case WAIT_EVENT_AUTOVACUUM_MAIN:
+                       event_name = "AutoVacuumMain";
+                       break;
+               case WAIT_EVENT_BGWRITER_HIBERNATE:
+                       event_name = "BgWriterHibernate";
+                       break;
+               case WAIT_EVENT_BGWRITER_MAIN:
+                       event_name = "BgWriterMain";
+                       break;
+               case WAIT_EVENT_CHECKPOINTER_MAIN:
+                       event_name = "CheckpointerMain";
+                       break;
+               case WAIT_EVENT_LOGICAL_APPLY_MAIN:
+                       event_name = "LogicalApplyMain";
+                       break;
+               case WAIT_EVENT_LOGICAL_LAUNCHER_MAIN:
+                       event_name = "LogicalLauncherMain";
+                       break;
+               case WAIT_EVENT_PGSTAT_MAIN:
+                       event_name = "PgStatMain";
+                       break;
+               case WAIT_EVENT_RECOVERY_WAL_ALL:
+                       event_name = "RecoveryWalAll";
+                       break;
+               case WAIT_EVENT_RECOVERY_WAL_STREAM:
+                       event_name = "RecoveryWalStream";
+                       break;
+               case WAIT_EVENT_SYSLOGGER_MAIN:
+                       event_name = "SysLoggerMain";
+                       break;
+               case WAIT_EVENT_WAL_RECEIVER_MAIN:
+                       event_name = "WalReceiverMain";
+                       break;
+               case WAIT_EVENT_WAL_SENDER_MAIN:
+                       event_name = "WalSenderMain";
+                       break;
+               case WAIT_EVENT_WAL_WRITER_MAIN:
+                       event_name = "WalWriterMain";
+                       break;
+                       /* no default case, so that compiler will warn */
+       }
+
+       return event_name;
+}
+
+/* ----------
+ * pgstat_get_wait_client() -
+ *
+ * Convert WaitEventClient to string.
+ * ----------
+ */
+static const char *
+pgstat_get_wait_client(WaitEventClient w)
+{
+       const char *event_name = "unknown wait event";
+
+       switch (w)
+       {
+               case WAIT_EVENT_CLIENT_READ:
+                       event_name = "ClientRead";
+                       break;
+               case WAIT_EVENT_CLIENT_WRITE:
+                       event_name = "ClientWrite";
+                       break;
+               case WAIT_EVENT_LIBPQWALRECEIVER_CONNECT:
+                       event_name = "LibPQWalReceiverConnect";
+                       break;
+               case WAIT_EVENT_LIBPQWALRECEIVER_RECEIVE:
+                       event_name = "LibPQWalReceiverReceive";
+                       break;
+               case WAIT_EVENT_SSL_OPEN_SERVER:
+                       event_name = "SSLOpenServer";
+                       break;
+               case WAIT_EVENT_WAL_RECEIVER_WAIT_START:
+                       event_name = "WalReceiverWaitStart";
+                       break;
+               case WAIT_EVENT_WAL_SENDER_WAIT_WAL:
+                       event_name = "WalSenderWaitForWAL";
+                       break;
+               case WAIT_EVENT_WAL_SENDER_WRITE_DATA:
+                       event_name = "WalSenderWriteData";
+                       break;
+               case WAIT_EVENT_GSS_OPEN_SERVER:
+                       event_name = "GSSOpenServer";
+                       break;
+                       /* no default case, so that compiler will warn */
+       }
+
+       return event_name;
+}
+
+/* ----------
+ * pgstat_get_wait_ipc() -
+ *
+ * Convert WaitEventIPC to string.
+ * ----------
+ */
+static const char *
+pgstat_get_wait_ipc(WaitEventIPC w)
+{
+       const char *event_name = "unknown wait event";
+
+       switch (w)
+       {
+               case WAIT_EVENT_BGWORKER_SHUTDOWN:
+                       event_name = "BgWorkerShutdown";
+                       break;
+               case WAIT_EVENT_BGWORKER_STARTUP:
+                       event_name = "BgWorkerStartup";
+                       break;
+               case WAIT_EVENT_BTREE_PAGE:
+                       event_name = "BtreePage";
+                       break;
+               case WAIT_EVENT_CHECKPOINT_DONE:
+                       event_name = "CheckpointDone";
+                       break;
+               case WAIT_EVENT_CHECKPOINT_START:
+                       event_name = "CheckpointStart";
+                       break;
+               case WAIT_EVENT_CLOG_GROUP_UPDATE:
+                       event_name = "ClogGroupUpdate";
+                       break;
+               case WAIT_EVENT_EXECUTE_GATHER:
+                       event_name = "ExecuteGather";
+                       break;
+               case WAIT_EVENT_HASH_BATCH_ALLOCATING:
+                       event_name = "Hash/Batch/Allocating";
+                       break;
+               case WAIT_EVENT_HASH_BATCH_ELECTING:
+                       event_name = "Hash/Batch/Electing";
+                       break;
+               case WAIT_EVENT_HASH_BATCH_LOADING:
+                       event_name = "Hash/Batch/Loading";
+                       break;
+               case WAIT_EVENT_HASH_BUILD_ALLOCATING:
+                       event_name = "Hash/Build/Allocating";
+                       break;
+               case WAIT_EVENT_HASH_BUILD_ELECTING:
+                       event_name = "Hash/Build/Electing";
+                       break;
+               case WAIT_EVENT_HASH_BUILD_HASHING_INNER:
+                       event_name = "Hash/Build/HashingInner";
+                       break;
+               case WAIT_EVENT_HASH_BUILD_HASHING_OUTER:
+                       event_name = "Hash/Build/HashingOuter";
+                       break;
+               case WAIT_EVENT_HASH_GROW_BATCHES_ALLOCATING:
+                       event_name = "Hash/GrowBatches/Allocating";
+                       break;
+               case WAIT_EVENT_HASH_GROW_BATCHES_DECIDING:
+                       event_name = "Hash/GrowBatches/Deciding";
+                       break;
+               case WAIT_EVENT_HASH_GROW_BATCHES_ELECTING:
+                       event_name = "Hash/GrowBatches/Electing";
+                       break;
+               case WAIT_EVENT_HASH_GROW_BATCHES_FINISHING:
+                       event_name = "Hash/GrowBatches/Finishing";
+                       break;
+               case WAIT_EVENT_HASH_GROW_BATCHES_REPARTITIONING:
+                       event_name = "Hash/GrowBatches/Repartitioning";
+                       break;
+               case WAIT_EVENT_HASH_GROW_BUCKETS_ALLOCATING:
+                       event_name = "Hash/GrowBuckets/Allocating";
+                       break;
+               case WAIT_EVENT_HASH_GROW_BUCKETS_ELECTING:
+                       event_name = "Hash/GrowBuckets/Electing";
+                       break;
+               case WAIT_EVENT_HASH_GROW_BUCKETS_REINSERTING:
+                       event_name = "Hash/GrowBuckets/Reinserting";
+                       break;
+               case WAIT_EVENT_LOGICAL_SYNC_DATA:
+                       event_name = "LogicalSyncData";
+                       break;
+               case WAIT_EVENT_LOGICAL_SYNC_STATE_CHANGE:
+                       event_name = "LogicalSyncStateChange";
+                       break;
+               case WAIT_EVENT_MQ_INTERNAL:
+                       event_name = "MessageQueueInternal";
+                       break;
+               case WAIT_EVENT_MQ_PUT_MESSAGE:
+                       event_name = "MessageQueuePutMessage";
+                       break;
+               case WAIT_EVENT_MQ_RECEIVE:
+                       event_name = "MessageQueueReceive";
+                       break;
+               case WAIT_EVENT_MQ_SEND:
+                       event_name = "MessageQueueSend";
+                       break;
+               case WAIT_EVENT_PARALLEL_BITMAP_SCAN:
+                       event_name = "ParallelBitmapScan";
+                       break;
+               case WAIT_EVENT_PARALLEL_CREATE_INDEX_SCAN:
+                       event_name = "ParallelCreateIndexScan";
+                       break;
+               case WAIT_EVENT_PARALLEL_FINISH:
+                       event_name = "ParallelFinish";
+                       break;
+               case WAIT_EVENT_PROCARRAY_GROUP_UPDATE:
+                       event_name = "ProcArrayGroupUpdate";
+                       break;
+               case WAIT_EVENT_PROMOTE:
+                       event_name = "Promote";
+                       break;
+               case WAIT_EVENT_REPLICATION_ORIGIN_DROP:
+                       event_name = "ReplicationOriginDrop";
+                       break;
+               case WAIT_EVENT_REPLICATION_SLOT_DROP:
+                       event_name = "ReplicationSlotDrop";
+                       break;
+               case WAIT_EVENT_SAFE_SNAPSHOT:
+                       event_name = "SafeSnapshot";
+                       break;
+               case WAIT_EVENT_SYNC_REP:
+                       event_name = "SyncRep";
+                       break;
+                       /* no default case, so that compiler will warn */
+       }
+
+       return event_name;
+}
+
+/* ----------
+ * pgstat_get_wait_timeout() -
+ *
+ * Convert WaitEventTimeout to string.
+ * ----------
+ */
+static const char *
+pgstat_get_wait_timeout(WaitEventTimeout w)
+{
+       const char *event_name = "unknown wait event";
+
+       switch (w)
+       {
+               case WAIT_EVENT_BASE_BACKUP_THROTTLE:
+                       event_name = "BaseBackupThrottle";
+                       break;
+               case WAIT_EVENT_PG_SLEEP:
+                       event_name = "PgSleep";
+                       break;
+               case WAIT_EVENT_RECOVERY_APPLY_DELAY:
+                       event_name = "RecoveryApplyDelay";
+                       break;
+                       /* no default case, so that compiler will warn */
+       }
+
+       return event_name;
+}
+
+/* ----------
+ * pgstat_get_wait_io() -
+ *
+ * Convert WaitEventIO to string.
+ * ----------
+ */
+static const char *
+pgstat_get_wait_io(WaitEventIO w)
+{
+       const char *event_name = "unknown wait event";
+
+       switch (w)
+       {
+               case WAIT_EVENT_BUFFILE_READ:
+                       event_name = "BufFileRead";
+                       break;
+               case WAIT_EVENT_BUFFILE_WRITE:
+                       event_name = "BufFileWrite";
+                       break;
+               case WAIT_EVENT_CONTROL_FILE_READ:
+                       event_name = "ControlFileRead";
+                       break;
+               case WAIT_EVENT_CONTROL_FILE_SYNC:
+                       event_name = "ControlFileSync";
+                       break;
+               case WAIT_EVENT_CONTROL_FILE_SYNC_UPDATE:
+                       event_name = "ControlFileSyncUpdate";
+                       break;
+               case WAIT_EVENT_CONTROL_FILE_WRITE:
+                       event_name = "ControlFileWrite";
+                       break;
+               case WAIT_EVENT_CONTROL_FILE_WRITE_UPDATE:
+                       event_name = "ControlFileWriteUpdate";
+                       break;
+               case WAIT_EVENT_COPY_FILE_READ:
+                       event_name = "CopyFileRead";
+                       break;
+               case WAIT_EVENT_COPY_FILE_WRITE:
+                       event_name = "CopyFileWrite";
+                       break;
+               case WAIT_EVENT_DATA_FILE_EXTEND:
+                       event_name = "DataFileExtend";
+                       break;
+               case WAIT_EVENT_DATA_FILE_FLUSH:
+                       event_name = "DataFileFlush";
+                       break;
+               case WAIT_EVENT_DATA_FILE_IMMEDIATE_SYNC:
+                       event_name = "DataFileImmediateSync";
+                       break;
+               case WAIT_EVENT_DATA_FILE_PREFETCH:
+                       event_name = "DataFilePrefetch";
+                       break;
+               case WAIT_EVENT_DATA_FILE_READ:
+                       event_name = "DataFileRead";
+                       break;
+               case WAIT_EVENT_DATA_FILE_SYNC:
+                       event_name = "DataFileSync";
+                       break;
+               case WAIT_EVENT_DATA_FILE_TRUNCATE:
+                       event_name = "DataFileTruncate";
+                       break;
+               case WAIT_EVENT_DATA_FILE_WRITE:
+                       event_name = "DataFileWrite";
+                       break;
+               case WAIT_EVENT_DSM_FILL_ZERO_WRITE:
+                       event_name = "DSMFillZeroWrite";
+                       break;
+               case WAIT_EVENT_LOCK_FILE_ADDTODATADIR_READ:
+                       event_name = "LockFileAddToDataDirRead";
+                       break;
+               case WAIT_EVENT_LOCK_FILE_ADDTODATADIR_SYNC:
+                       event_name = "LockFileAddToDataDirSync";
+                       break;
+               case WAIT_EVENT_LOCK_FILE_ADDTODATADIR_WRITE:
+                       event_name = "LockFileAddToDataDirWrite";
+                       break;
+               case WAIT_EVENT_LOCK_FILE_CREATE_READ:
+                       event_name = "LockFileCreateRead";
+                       break;
+               case WAIT_EVENT_LOCK_FILE_CREATE_SYNC:
+                       event_name = "LockFileCreateSync";
+                       break;
+               case WAIT_EVENT_LOCK_FILE_CREATE_WRITE:
+                       event_name = "LockFileCreateWrite";
+                       break;
+               case WAIT_EVENT_LOCK_FILE_RECHECKDATADIR_READ:
+                       event_name = "LockFileReCheckDataDirRead";
+                       break;
+               case WAIT_EVENT_LOGICAL_REWRITE_CHECKPOINT_SYNC:
+                       event_name = "LogicalRewriteCheckpointSync";
+                       break;
+               case WAIT_EVENT_LOGICAL_REWRITE_MAPPING_SYNC:
+                       event_name = "LogicalRewriteMappingSync";
+                       break;
+               case WAIT_EVENT_LOGICAL_REWRITE_MAPPING_WRITE:
+                       event_name = "LogicalRewriteMappingWrite";
+                       break;
+               case WAIT_EVENT_LOGICAL_REWRITE_SYNC:
+                       event_name = "LogicalRewriteSync";
+                       break;
+               case WAIT_EVENT_LOGICAL_REWRITE_TRUNCATE:
+                       event_name = "LogicalRewriteTruncate";
+                       break;
+               case WAIT_EVENT_LOGICAL_REWRITE_WRITE:
+                       event_name = "LogicalRewriteWrite";
+                       break;
+               case WAIT_EVENT_RELATION_MAP_READ:
+                       event_name = "RelationMapRead";
+                       break;
+               case WAIT_EVENT_RELATION_MAP_SYNC:
+                       event_name = "RelationMapSync";
+                       break;
+               case WAIT_EVENT_RELATION_MAP_WRITE:
+                       event_name = "RelationMapWrite";
+                       break;
+               case WAIT_EVENT_REORDER_BUFFER_READ:
+                       event_name = "ReorderBufferRead";
+                       break;
+               case WAIT_EVENT_REORDER_BUFFER_WRITE:
+                       event_name = "ReorderBufferWrite";
+                       break;
+               case WAIT_EVENT_REORDER_LOGICAL_MAPPING_READ:
+                       event_name = "ReorderLogicalMappingRead";
+                       break;
+               case WAIT_EVENT_REPLICATION_SLOT_READ:
+                       event_name = "ReplicationSlotRead";
+                       break;
+               case WAIT_EVENT_REPLICATION_SLOT_RESTORE_SYNC:
+                       event_name = "ReplicationSlotRestoreSync";
+                       break;
+               case WAIT_EVENT_REPLICATION_SLOT_SYNC:
+                       event_name = "ReplicationSlotSync";
+                       break;
+               case WAIT_EVENT_REPLICATION_SLOT_WRITE:
+                       event_name = "ReplicationSlotWrite";
+                       break;
+               case WAIT_EVENT_SLRU_FLUSH_SYNC:
+                       event_name = "SLRUFlushSync";
+                       break;
+               case WAIT_EVENT_SLRU_READ:
+                       event_name = "SLRURead";
+                       break;
+               case WAIT_EVENT_SLRU_SYNC:
+                       event_name = "SLRUSync";
+                       break;
+               case WAIT_EVENT_SLRU_WRITE:
+                       event_name = "SLRUWrite";
+                       break;
+               case WAIT_EVENT_SNAPBUILD_READ:
+                       event_name = "SnapbuildRead";
+                       break;
+               case WAIT_EVENT_SNAPBUILD_SYNC:
+                       event_name = "SnapbuildSync";
+                       break;
+               case WAIT_EVENT_SNAPBUILD_WRITE:
+                       event_name = "SnapbuildWrite";
+                       break;
+               case WAIT_EVENT_TIMELINE_HISTORY_FILE_SYNC:
+                       event_name = "TimelineHistoryFileSync";
+                       break;
+               case WAIT_EVENT_TIMELINE_HISTORY_FILE_WRITE:
+                       event_name = "TimelineHistoryFileWrite";
+                       break;
+               case WAIT_EVENT_TIMELINE_HISTORY_READ:
+                       event_name = "TimelineHistoryRead";
+                       break;
+               case WAIT_EVENT_TIMELINE_HISTORY_SYNC:
+                       event_name = "TimelineHistorySync";
+                       break;
+               case WAIT_EVENT_TIMELINE_HISTORY_WRITE:
+                       event_name = "TimelineHistoryWrite";
+                       break;
+               case WAIT_EVENT_TWOPHASE_FILE_READ:
+                       event_name = "TwophaseFileRead";
+                       break;
+               case WAIT_EVENT_TWOPHASE_FILE_SYNC:
+                       event_name = "TwophaseFileSync";
+                       break;
+               case WAIT_EVENT_TWOPHASE_FILE_WRITE:
+                       event_name = "TwophaseFileWrite";
+                       break;
+               case WAIT_EVENT_WALSENDER_TIMELINE_HISTORY_READ:
+                       event_name = "WALSenderTimelineHistoryRead";
+                       break;
+               case WAIT_EVENT_WAL_BOOTSTRAP_SYNC:
+                       event_name = "WALBootstrapSync";
+                       break;
+               case WAIT_EVENT_WAL_BOOTSTRAP_WRITE:
+                       event_name = "WALBootstrapWrite";
+                       break;
+               case WAIT_EVENT_WAL_COPY_READ:
+                       event_name = "WALCopyRead";
+                       break;
+               case WAIT_EVENT_WAL_COPY_SYNC:
+                       event_name = "WALCopySync";
+                       break;
+               case WAIT_EVENT_WAL_COPY_WRITE:
+                       event_name = "WALCopyWrite";
+                       break;
+               case WAIT_EVENT_WAL_INIT_SYNC:
+                       event_name = "WALInitSync";
+                       break;
+               case WAIT_EVENT_WAL_INIT_WRITE:
+                       event_name = "WALInitWrite";
+                       break;
+               case WAIT_EVENT_WAL_READ:
+                       event_name = "WALRead";
+                       break;
+               case WAIT_EVENT_WAL_SYNC:
+                       event_name = "WALSync";
+                       break;
+               case WAIT_EVENT_WAL_SYNC_METHOD_ASSIGN:
+                       event_name = "WALSyncMethodAssign";
+                       break;
+               case WAIT_EVENT_WAL_WRITE:
+                       event_name = "WALWrite";
+                       break;
+
+                       /* no default case, so that compiler will warn */
+       }
+
+       return event_name;
+}
+
 
 /* ----------
  * pgstat_get_backend_current_activity() -
@@ -2926,12 +4077,17 @@ pgstat_get_backend_current_activity(int pid, bool checkUser)
 
                for (;;)
                {
-                       int                     save_changecount = vbeentry->st_changecount;
+                       int                     before_changecount;
+                       int                     after_changecount;
+
+                       pgstat_save_changecount_before(vbeentry, before_changecount);
 
                        found = (vbeentry->st_procpid == pid);
 
-                       if (save_changecount == vbeentry->st_changecount &&
-                               (save_changecount & 1) == 0)
+                       pgstat_save_changecount_after(vbeentry, after_changecount);
+
+                       if (before_changecount == after_changecount &&
+                               (before_changecount & 1) == 0)
                                break;
 
                        /* Make sure we can break out of loop if stuck... */
@@ -2943,10 +4099,13 @@ pgstat_get_backend_current_activity(int pid, bool checkUser)
                        /* Now it is safe to use the non-volatile pointer */
                        if (checkUser && !superuser() && beentry->st_userid != GetUserId())
                                return "<insufficient privilege>";
-                       else if (*(beentry->st_activity) == '\0')
+                       else if (*(beentry->st_activity_raw) == '\0')
                                return "<command string not enabled>";
                        else
-                               return beentry->st_activity;
+                       {
+                               /* this'll leak a bit of memory, but that seems acceptable */
+                               return pgstat_clip_activity(beentry->st_activity_raw);
+                       }
                }
 
                beentry++;
@@ -2992,7 +4151,7 @@ pgstat_get_crashed_backend_activity(int pid, char *buffer, int buflen)
                if (beentry->st_procpid == pid)
                {
                        /* Read pointer just once, so it can't change after validation */
-                       const char *activity = beentry->st_activity;
+                       const char *activity = beentry->st_activity_raw;
                        const char *activity_last;
 
                        /*
@@ -3015,7 +4174,8 @@ pgstat_get_crashed_backend_activity(int pid, char *buffer, int buflen)
                        /*
                         * Copy only ASCII-safe characters so we don't run into encoding
                         * problems when reporting the message; and be sure not to run off
-                        * the end of memory.
+                        * the end of memory.  As only ASCII characters are reported, it
+                        * doesn't seem necessary to perform multibyte aware clipping.
                         */
                        ascii_safe_strlcpy(buffer, activity,
                                                           Min(buflen, pgstat_track_activity_query_size));
@@ -3030,6 +4190,47 @@ pgstat_get_crashed_backend_activity(int pid, char *buffer, int buflen)
        return NULL;
 }
 
+const char *
+pgstat_get_backend_desc(BackendType backendType)
+{
+       const char *backendDesc = "unknown process type";
+
+       switch (backendType)
+       {
+               case B_AUTOVAC_LAUNCHER:
+                       backendDesc = "autovacuum launcher";
+                       break;
+               case B_AUTOVAC_WORKER:
+                       backendDesc = "autovacuum worker";
+                       break;
+               case B_BACKEND:
+                       backendDesc = "client backend";
+                       break;
+               case B_BG_WORKER:
+                       backendDesc = "background worker";
+                       break;
+               case B_BG_WRITER:
+                       backendDesc = "background writer";
+                       break;
+               case B_CHECKPOINTER:
+                       backendDesc = "checkpointer";
+                       break;
+               case B_STARTUP:
+                       backendDesc = "startup";
+                       break;
+               case B_WAL_RECEIVER:
+                       backendDesc = "walreceiver";
+                       break;
+               case B_WAL_SENDER:
+                       backendDesc = "walsender";
+                       break;
+               case B_WAL_WRITER:
+                       backendDesc = "walwriter";
+                       break;
+       }
+
+       return backendDesc;
+}
 
 /* ------------------------------------------------------------
  * Local support functions follow
@@ -3096,7 +4297,7 @@ pgstat_send_archiver(const char *xlog, bool failed)
         */
        pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_ARCHIVER);
        msg.m_failed = failed;
-       strncpy(msg.m_xlog, xlog, sizeof(msg.m_xlog));
+       StrNCpy(msg.m_xlog, xlog, sizeof(msg.m_xlog));
        msg.m_timestamp = GetCurrentTimestamp();
        pgstat_send(&msg, sizeof(msg));
 }
@@ -3150,32 +4351,10 @@ PgstatCollectorMain(int argc, char *argv[])
        PgStat_Msg      msg;
        int                     wr;
 
-       IsUnderPostmaster = true;       /* we are a postmaster subprocess now */
-
-       MyProcPid = getpid();           /* reset MyProcPid */
-
-       MyStartTime = time(NULL);       /* record Start Time for logging */
-
-       /*
-        * If possible, make this process a group leader, so that the postmaster
-        * can signal any child processes too.  (pgstat probably never has any
-        * child processes, but for consistency we make all postmaster child
-        * processes do this.)
-        */
-#ifdef HAVE_SETSID
-       if (setsid() < 0)
-               elog(FATAL, "setsid() failed: %m");
-#endif
-
-       InitializeLatchSupport();       /* needed for latch waits */
-
-       /* Initialize private latch for use by signal handlers */
-       InitLatch(&pgStatLatch);
-
        /*
         * Ignore all signals usually bound to some action in the postmaster,
         * except SIGHUP and SIGQUIT.  Note we don't need a SIGUSR1 handler to
-        * support latch operations, because pgStatLatch is local not shared.
+        * support latch operations, because we only use a local latch.
         */
        pqsignal(SIGHUP, pgstat_sighup_handler);
        pqsignal(SIGINT, SIG_IGN);
@@ -3185,21 +4364,17 @@ PgstatCollectorMain(int argc, char *argv[])
        pqsignal(SIGPIPE, SIG_IGN);
        pqsignal(SIGUSR1, SIG_IGN);
        pqsignal(SIGUSR2, SIG_IGN);
+       /* Reset some signals that are accepted by postmaster but not here */
        pqsignal(SIGCHLD, SIG_DFL);
-       pqsignal(SIGTTIN, SIG_DFL);
-       pqsignal(SIGTTOU, SIG_DFL);
-       pqsignal(SIGCONT, SIG_DFL);
-       pqsignal(SIGWINCH, SIG_DFL);
        PG_SETMASK(&UnBlockSig);
 
        /*
         * Identify myself via ps
         */
-       init_ps_display("stats collector process", "", "", "");
+       init_ps_display("stats collector", "", "", "");
 
        /*
-        * Read in an existing statistics stats file or initialize the stats to
-        * zero.
+        * Read in existing stats files or initialize the stats to zero.
         */
        pgStatRunningInCollector = true;
        pgStatDBHash = pgstat_read_statsfiles(InvalidOid, true, true);
@@ -3221,7 +4396,7 @@ PgstatCollectorMain(int argc, char *argv[])
        for (;;)
        {
                /* Clear any already-pending wakeups */
-               ResetLatch(&pgStatLatch);
+               ResetLatch(MyLatch);
 
                /*
                 * Quit if we get SIGQUIT from the postmaster.
@@ -3245,8 +4420,8 @@ PgstatCollectorMain(int argc, char *argv[])
                        }
 
                        /*
-                        * Write the stats file if a new request has arrived that is not
-                        * satisfied by existing file.
+                        * Write the stats file(s) if a new request has arrived that is
+                        * not satisfied by existing file(s).
                         */
                        if (pgstat_write_statsfile_needed())
                                pgstat_write_statsfiles(false, false);
@@ -3322,13 +4497,13 @@ PgstatCollectorMain(int argc, char *argv[])
 
                                case PGSTAT_MTYPE_RESETSHAREDCOUNTER:
                                        pgstat_recv_resetsharedcounter(
-                                                                          (PgStat_MsgResetsharedcounter *) &msg,
+                                                                                                  (PgStat_MsgResetsharedcounter *) &msg,
                                                                                                   len);
                                        break;
 
                                case PGSTAT_MTYPE_RESETSINGLECOUNTER:
                                        pgstat_recv_resetsinglecounter(
-                                                                          (PgStat_MsgResetsinglecounter *) &msg,
+                                                                                                  (PgStat_MsgResetsinglecounter *) &msg,
                                                                                                   len);
                                        break;
 
@@ -3372,6 +4547,10 @@ PgstatCollectorMain(int argc, char *argv[])
                                        pgstat_recv_tempfile((PgStat_MsgTempFile *) &msg, len);
                                        break;
 
+                               case PGSTAT_MTYPE_CHECKSUMFAILURE:
+                                       pgstat_recv_checksum_failure((PgStat_MsgChecksumFailure *) &msg, len);
+                                       break;
+
                                default:
                                        break;
                        }
@@ -3379,10 +4558,10 @@ PgstatCollectorMain(int argc, char *argv[])
 
                /* Sleep until there's something to do */
 #ifndef WIN32
-               wr = WaitLatchOrSocket(&pgStatLatch,
-                                        WL_LATCH_SET | WL_POSTMASTER_DEATH | WL_SOCKET_READABLE,
-                                                          pgStatSock,
-                                                          -1L);
+               wr = WaitLatchOrSocket(MyLatch,
+                                                          WL_LATCH_SET | WL_POSTMASTER_DEATH | WL_SOCKET_READABLE,
+                                                          pgStatSock, -1L,
+                                                          WAIT_EVENT_PGSTAT_MAIN);
 #else
 
                /*
@@ -3392,13 +4571,14 @@ PgstatCollectorMain(int argc, char *argv[])
                 * first water, but until somebody wants to debug exactly what's
                 * happening there, this is the best we can do.  The two-second
                 * timeout matches our pre-9.2 behavior, and needs to be short enough
-                * to not provoke "pgstat wait timeout" complaints from
+                * to not provoke "using stale statistics" complaints from
                 * backend_read_statsfile.
                 */
-               wr = WaitLatchOrSocket(&pgStatLatch,
-               WL_LATCH_SET | WL_POSTMASTER_DEATH | WL_SOCKET_READABLE | WL_TIMEOUT,
+               wr = WaitLatchOrSocket(MyLatch,
+                                                          WL_LATCH_SET | WL_POSTMASTER_DEATH | WL_SOCKET_READABLE | WL_TIMEOUT,
                                                           pgStatSock,
-                                                          2 * 1000L /* msec */ );
+                                                          2 * 1000L /* msec */ ,
+                                                          WAIT_EVENT_PGSTAT_MAIN);
 #endif
 
                /*
@@ -3425,7 +4605,7 @@ pgstat_exit(SIGNAL_ARGS)
        int                     save_errno = errno;
 
        need_exit = true;
-       SetLatch(&pgStatLatch);
+       SetLatch(MyLatch);
 
        errno = save_errno;
 }
@@ -3437,7 +4617,7 @@ pgstat_sighup_handler(SIGNAL_ARGS)
        int                     save_errno = errno;
 
        got_SIGHUP = true;
-       SetLatch(&pgStatLatch);
+       SetLatch(MyLatch);
 
        errno = save_errno;
 }
@@ -3470,6 +4650,7 @@ reset_dbentry_counters(PgStat_StatDBEntry *dbentry)
        dbentry->n_temp_files = 0;
        dbentry->n_temp_bytes = 0;
        dbentry->n_deadlocks = 0;
+       dbentry->n_checksum_failures = 0;
        dbentry->n_block_read_time = 0;
        dbentry->n_block_write_time = 0;
 
@@ -3479,19 +4660,17 @@ reset_dbentry_counters(PgStat_StatDBEntry *dbentry)
        memset(&hash_ctl, 0, sizeof(hash_ctl));
        hash_ctl.keysize = sizeof(Oid);
        hash_ctl.entrysize = sizeof(PgStat_StatTabEntry);
-       hash_ctl.hash = oid_hash;
        dbentry->tables = hash_create("Per-database table",
                                                                  PGSTAT_TAB_HASH_SIZE,
                                                                  &hash_ctl,
-                                                                 HASH_ELEM | HASH_FUNCTION);
+                                                                 HASH_ELEM | HASH_BLOBS);
 
        hash_ctl.keysize = sizeof(Oid);
        hash_ctl.entrysize = sizeof(PgStat_StatFuncEntry);
-       hash_ctl.hash = oid_hash;
        dbentry->functions = hash_create("Per-database function",
                                                                         PGSTAT_FUNCTION_HASH_SIZE,
                                                                         &hash_ctl,
-                                                                        HASH_ELEM | HASH_FUNCTION);
+                                                                        HASH_ELEM | HASH_BLOBS);
 }
 
 /*
@@ -3578,14 +4757,14 @@ pgstat_get_tab_entry(PgStat_StatDBEntry *dbentry, Oid tableoid, bool create)
  * pgstat_write_statsfiles() -
  *             Write the global statistics file, as well as requested DB files.
  *
- *     If writing to the permanent files (happens when the collector is
- *     shutting down only), remove the temporary files so that backends
- *     starting up under a new postmaster can't read the old data before
- *     the new collector is ready.
+ *     'permanent' specifies writing to the permanent files not temporary ones.
+ *     When true (happens only when the collector is shutting down), also remove
+ *     the temporary files so that backends starting up under a new postmaster
+ *     can't read old data before the new collector is ready.
  *
  *     When 'allDbs' is false, only the requested databases (listed in
- *     last_statrequests) will be written; otherwise, all databases will be
- *     written.
+ *     pending_write_requests) will be written; otherwise, all databases
+ *     will be written.
  * ----------
  */
 static void
@@ -3599,7 +4778,7 @@ pgstat_write_statsfiles(bool permanent, bool allDbs)
        const char *statfile = permanent ? PGSTAT_STAT_PERMANENT_FILENAME : pgstat_stat_filename;
        int                     rc;
 
-       elog(DEBUG2, "writing statsfile '%s'", statfile);
+       elog(DEBUG2, "writing stats file \"%s\"", statfile);
 
        /*
         * Open the statistics temp file to write out the current values.
@@ -3645,15 +4824,14 @@ pgstat_write_statsfiles(bool permanent, bool allDbs)
        while ((dbentry = (PgStat_StatDBEntry *) hash_seq_search(&hstat)) != NULL)
        {
                /*
-                * Write out the tables and functions into the DB stat file, if
-                * required.
-                *
-                * We need to do this before the dbentry write, to ensure the
-                * timestamps written to both are consistent.
+                * Write out the table and function stats for this DB into the
+                * appropriate per-DB stat file, if required.
                 */
                if (allDbs || pgstat_db_requested(dbentry->databaseid))
                {
+                       /* Make DB's timestamp consistent with the global stats */
                        dbentry->stats_timestamp = globalStats.stats_timestamp;
+
                        pgstat_write_db_statsfile(dbentry, permanent);
                }
 
@@ -3677,8 +4855,8 @@ pgstat_write_statsfiles(bool permanent, bool allDbs)
        {
                ereport(LOG,
                                (errcode_for_file_access(),
-                          errmsg("could not write temporary statistics file \"%s\": %m",
-                                         tmpfile)));
+                                errmsg("could not write temporary statistics file \"%s\": %m",
+                                               tmpfile)));
                FreeFile(fpout);
                unlink(tmpfile);
        }
@@ -3686,8 +4864,8 @@ pgstat_write_statsfiles(bool permanent, bool allDbs)
        {
                ereport(LOG,
                                (errcode_for_file_access(),
-                          errmsg("could not close temporary statistics file \"%s\": %m",
-                                         tmpfile)));
+                                errmsg("could not close temporary statistics file \"%s\": %m",
+                                               tmpfile)));
                unlink(tmpfile);
        }
        else if (rename(tmpfile, statfile) < 0)
@@ -3706,27 +4884,8 @@ pgstat_write_statsfiles(bool permanent, bool allDbs)
         * Now throw away the list of requests.  Note that requests sent after we
         * started the write are still waiting on the network socket.
         */
-       if (!slist_is_empty(&last_statrequests))
-       {
-               slist_mutable_iter iter;
-
-               /*
-                * Strictly speaking we should do slist_delete_current() before
-                * freeing each request struct.  We skip that and instead
-                * re-initialize the list header at the end.  Nonetheless, we must use
-                * slist_foreach_modify, not just slist_foreach, since we will free
-                * the node's storage before advancing.
-                */
-               slist_foreach_modify(iter, &last_statrequests)
-               {
-                       DBWriteRequest *req;
-
-                       req = slist_container(DBWriteRequest, next, iter.cur);
-                       pfree(req);
-               }
-
-               slist_init(&last_statrequests);
-       }
+       list_free(pending_write_requests);
+       pending_write_requests = NIL;
 }
 
 /*
@@ -3745,7 +4904,7 @@ get_dbstat_filename(bool permanent, bool tempname, Oid databaseid,
                                           pgstat_stat_directory,
                                           databaseid,
                                           tempname ? "tmp" : "stat");
-       if (printed > len)
+       if (printed >= len)
                elog(ERROR, "overlength pgstat path");
 }
 
@@ -3776,7 +4935,7 @@ pgstat_write_db_statsfile(PgStat_StatDBEntry *dbentry, bool permanent)
        get_dbstat_filename(permanent, true, dbid, tmpfile, MAXPGPATH);
        get_dbstat_filename(permanent, false, dbid, statfile, MAXPGPATH);
 
-       elog(DEBUG2, "writing statsfile '%s'", statfile);
+       elog(DEBUG2, "writing stats file \"%s\"", statfile);
 
        /*
         * Open the statistics temp file to write out the current values.
@@ -3831,8 +4990,8 @@ pgstat_write_db_statsfile(PgStat_StatDBEntry *dbentry, bool permanent)
        {
                ereport(LOG,
                                (errcode_for_file_access(),
-                          errmsg("could not write temporary statistics file \"%s\": %m",
-                                         tmpfile)));
+                                errmsg("could not write temporary statistics file \"%s\": %m",
+                                               tmpfile)));
                FreeFile(fpout);
                unlink(tmpfile);
        }
@@ -3840,8 +4999,8 @@ pgstat_write_db_statsfile(PgStat_StatDBEntry *dbentry, bool permanent)
        {
                ereport(LOG,
                                (errcode_for_file_access(),
-                          errmsg("could not close temporary statistics file \"%s\": %m",
-                                         tmpfile)));
+                                errmsg("could not close temporary statistics file \"%s\": %m",
+                                               tmpfile)));
                unlink(tmpfile);
        }
        else if (rename(tmpfile, statfile) < 0)
@@ -3857,7 +5016,7 @@ pgstat_write_db_statsfile(PgStat_StatDBEntry *dbentry, bool permanent)
        {
                get_dbstat_filename(false, false, dbid, statfile, MAXPGPATH);
 
-               elog(DEBUG2, "removing temporary stat file '%s'", statfile);
+               elog(DEBUG2, "removing temporary stats file \"%s\"", statfile);
                unlink(statfile);
        }
 }
@@ -3865,13 +5024,20 @@ pgstat_write_db_statsfile(PgStat_StatDBEntry *dbentry, bool permanent)
 /* ----------
  * pgstat_read_statsfiles() -
  *
- *     Reads in the existing statistics collector files and initializes the
- *     databases' hash table.  If the permanent file name is requested (which
- *     only happens in the stats collector itself), also remove the file after
- *     reading; the in-memory status is now authoritative, and the permanent file
- *     would be out of date in case somebody else reads it.
+ *     Reads in some existing statistics collector files and returns the
+ *     databases hash table that is the top level of the data.
+ *
+ *     If 'onlydb' is not InvalidOid, it means we only want data for that DB
+ *     plus the shared catalogs ("DB 0").  We'll still populate the DB hash
+ *     table for all databases, but we don't bother even creating table/function
+ *     hash tables for other databases.
  *
- *     If a deep read is requested, table/function stats are read also, otherwise
+ *     'permanent' specifies reading from the permanent files not temporary ones.
+ *     When true (happens only when the collector is starting up), remove the
+ *     files after reading; the in-memory status is now authoritative, and the
+ *     files would be out of date in case somebody else reads them.
+ *
+ *     If a 'deep' read is requested, table/function stats are read, otherwise
  *     the table/function hash tables remain empty.
  * ----------
  */
@@ -3898,10 +5064,9 @@ pgstat_read_statsfiles(Oid onlydb, bool permanent, bool deep)
        memset(&hash_ctl, 0, sizeof(hash_ctl));
        hash_ctl.keysize = sizeof(Oid);
        hash_ctl.entrysize = sizeof(PgStat_StatDBEntry);
-       hash_ctl.hash = oid_hash;
        hash_ctl.hcxt = pgStatLocalContext;
        dbhash = hash_create("Databases hash", PGSTAT_DB_HASH_SIZE, &hash_ctl,
-                                                HASH_ELEM | HASH_FUNCTION | HASH_CONTEXT);
+                                                HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
 
        /*
         * Clear out global and archiver statistics so they start from zero in
@@ -3954,9 +5119,20 @@ pgstat_read_statsfiles(Oid onlydb, bool permanent, bool deep)
        {
                ereport(pgStatRunningInCollector ? LOG : WARNING,
                                (errmsg("corrupted statistics file \"%s\"", statfile)));
+               memset(&globalStats, 0, sizeof(globalStats));
                goto done;
        }
 
+       /*
+        * In the collector, disregard the timestamp we read from the permanent
+        * stats file; we should be willing to write a temp stats file immediately
+        * upon the first request from any backend.  This only matters if the old
+        * file's timestamp is less than PGSTAT_STAT_INTERVAL ago, but that's not
+        * an unusual scenario.
+        */
+       if (pgStatRunningInCollector)
+               globalStats.stats_timestamp = 0;
+
        /*
         * Read archiver stats struct
         */
@@ -3964,6 +5140,7 @@ pgstat_read_statsfiles(Oid onlydb, bool permanent, bool deep)
        {
                ereport(pgStatRunningInCollector ? LOG : WARNING,
                                (errmsg("corrupted statistics file \"%s\"", statfile)));
+               memset(&archiverStats, 0, sizeof(archiverStats));
                goto done;
        }
 
@@ -3993,7 +5170,7 @@ pgstat_read_statsfiles(Oid onlydb, bool permanent, bool deep)
                                 * Add to the DB hash
                                 */
                                dbentry = (PgStat_StatDBEntry *) hash_search(dbhash,
-                                                                                                 (void *) &dbbuf.databaseid,
+                                                                                                                        (void *) &dbbuf.databaseid,
                                                                                                                         HASH_ENTER,
                                                                                                                         &found);
                                if (found)
@@ -4009,8 +5186,17 @@ pgstat_read_statsfiles(Oid onlydb, bool permanent, bool deep)
                                dbentry->functions = NULL;
 
                                /*
-                                * Don't collect tables if not the requested DB (or the
-                                * shared-table info)
+                                * In the collector, disregard the timestamp we read from the
+                                * permanent stats file; we should be willing to write a temp
+                                * stats file immediately upon the first request from any
+                                * backend.
+                                */
+                               if (pgStatRunningInCollector)
+                                       dbentry->stats_timestamp = 0;
+
+                               /*
+                                * Don't create tables/functions hashtables for uninteresting
+                                * databases.
                                 */
                                if (onlydb != InvalidOid)
                                {
@@ -4022,27 +5208,23 @@ pgstat_read_statsfiles(Oid onlydb, bool permanent, bool deep)
                                memset(&hash_ctl, 0, sizeof(hash_ctl));
                                hash_ctl.keysize = sizeof(Oid);
                                hash_ctl.entrysize = sizeof(PgStat_StatTabEntry);
-                               hash_ctl.hash = oid_hash;
                                hash_ctl.hcxt = pgStatLocalContext;
                                dbentry->tables = hash_create("Per-database table",
                                                                                          PGSTAT_TAB_HASH_SIZE,
                                                                                          &hash_ctl,
-                                                                  HASH_ELEM | HASH_FUNCTION | HASH_CONTEXT);
+                                                                                         HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
 
                                hash_ctl.keysize = sizeof(Oid);
                                hash_ctl.entrysize = sizeof(PgStat_StatFuncEntry);
-                               hash_ctl.hash = oid_hash;
                                hash_ctl.hcxt = pgStatLocalContext;
                                dbentry->functions = hash_create("Per-database function",
                                                                                                 PGSTAT_FUNCTION_HASH_SIZE,
                                                                                                 &hash_ctl,
-                                                                  HASH_ELEM | HASH_FUNCTION | HASH_CONTEXT);
+                                                                                                HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
 
                                /*
                                 * If requested, read the data from the database-specific
-                                * file. If there was onlydb specified (!= InvalidOid), we
-                                * would not get here because of a break above. So we don't
-                                * need to recheck.
+                                * file.  Otherwise we just leave the hashtables empty.
                                 */
                                if (deep)
                                        pgstat_read_db_statsfile(dbentry->databaseid,
@@ -4069,7 +5251,7 @@ done:
        /* If requested to read the permanent file, also get rid of it. */
        if (permanent)
        {
-               elog(DEBUG2, "removing permanent stats file '%s'", statfile);
+               elog(DEBUG2, "removing permanent stats file \"%s\"", statfile);
                unlink(statfile);
        }
 
@@ -4081,10 +5263,14 @@ done:
  * pgstat_read_db_statsfile() -
  *
  *     Reads in the existing statistics collector file for the given database,
- *     and initializes the tables and functions hash tables.
+ *     filling the passed-in tables and functions hash tables.
  *
- *     As pgstat_read_statsfiles, if the permanent file is requested, it is
+ *     As in pgstat_read_statsfiles, if the permanent file is requested, it is
  *     removed after reading.
+ *
+ *     Note: this code has the ability to skip storing per-table or per-function
+ *     data, if NULL is passed for the corresponding hashtable.  That's not used
+ *     at the moment though.
  * ----------
  */
 static void
@@ -4154,14 +5340,14 @@ pgstat_read_db_statsfile(Oid databaseid, HTAB *tabhash, HTAB *funchash,
                                }
 
                                /*
-                                * Skip if table belongs to a not requested database.
+                                * Skip if table data not wanted.
                                 */
                                if (tabhash == NULL)
                                        break;
 
                                tabentry = (PgStat_StatTabEntry *) hash_search(tabhash,
-                                                                                                       (void *) &tabbuf.tableid,
-                                                                                                                HASH_ENTER, &found);
+                                                                                                                          (void *) &tabbuf.tableid,
+                                                                                                                          HASH_ENTER, &found);
 
                                if (found)
                                {
@@ -4188,14 +5374,14 @@ pgstat_read_db_statsfile(Oid databaseid, HTAB *tabhash, HTAB *funchash,
                                }
 
                                /*
-                                * Skip if function belongs to a not requested database.
+                                * Skip if function data not wanted.
                                 */
                                if (funchash == NULL)
                                        break;
 
                                funcentry = (PgStat_StatFuncEntry *) hash_search(funchash,
-                                                                                               (void *) &funcbuf.functionid,
-                                                                                                                HASH_ENTER, &found);
+                                                                                                                                (void *) &funcbuf.functionid,
+                                                                                                                                HASH_ENTER, &found);
 
                                if (found)
                                {
@@ -4227,18 +5413,16 @@ done:
 
        if (permanent)
        {
-               elog(DEBUG2, "removing permanent stats file '%s'", statfile);
+               elog(DEBUG2, "removing permanent stats file \"%s\"", statfile);
                unlink(statfile);
        }
-
-       return;
 }
 
 /* ----------
  * pgstat_read_db_statsfile_timestamp() -
  *
  *     Attempt to determine the timestamp of the last db statfile write.
- *     Returns TRUE if successful; the timestamp is stored in *ts.
+ *     Returns true if successful; the timestamp is stored in *ts.
  *
  *     This needs to be careful about handling databases for which no stats file
  *     exists, such as databases without a stat entry or those not yet written:
@@ -4375,6 +5559,7 @@ backend_read_statsfile(void)
 {
        TimestampTz min_ts = 0;
        TimestampTz ref_ts = 0;
+       Oid                     inquiry_db;
        int                     count;
 
        /* already read it? */
@@ -4382,6 +5567,17 @@ backend_read_statsfile(void)
                return;
        Assert(!pgStatRunningInCollector);
 
+       /*
+        * In a normal backend, we check staleness of the data for our own DB, and
+        * so we send MyDatabaseId in inquiry messages.  In the autovac launcher,
+        * check staleness of the shared-catalog data, and send InvalidOid in
+        * inquiry messages so as not to force writing unnecessary data.
+        */
+       if (IsAutoVacuumLauncherProcess())
+               inquiry_db = InvalidOid;
+       else
+               inquiry_db = MyDatabaseId;
+
        /*
         * Loop until fresh enough stats file is available or we ran out of time.
         * The stats inquiry message is sent repeatedly in case collector drops
@@ -4395,7 +5591,7 @@ backend_read_statsfile(void)
 
                CHECK_FOR_INTERRUPTS();
 
-               ok = pgstat_read_db_statsfile_timestamp(MyDatabaseId, false, &file_ts);
+               ok = pgstat_read_db_statsfile_timestamp(inquiry_db, false, &file_ts);
 
                cur_ts = GetCurrentTimestamp();
                /* Calculate min acceptable timestamp, if we didn't already */
@@ -4454,7 +5650,7 @@ backend_read_statsfile(void)
                                pfree(mytime);
                        }
 
-                       pgstat_send_inquiry(cur_ts, min_ts, MyDatabaseId);
+                       pgstat_send_inquiry(cur_ts, min_ts, inquiry_db);
                        break;
                }
 
@@ -4464,17 +5660,20 @@ backend_read_statsfile(void)
 
                /* Not there or too old, so kick the collector and wait a bit */
                if ((count % PGSTAT_INQ_LOOP_COUNT) == 0)
-                       pgstat_send_inquiry(cur_ts, min_ts, MyDatabaseId);
+                       pgstat_send_inquiry(cur_ts, min_ts, inquiry_db);
 
                pg_usleep(PGSTAT_RETRY_DELAY * 1000L);
        }
 
        if (count >= PGSTAT_POLL_LOOP_COUNT)
-               elog(WARNING, "pgstat wait timeout");
+               ereport(LOG,
+                               (errmsg("using stale statistics instead of current ones "
+                                               "because stats collector is not responding")));
 
        /*
         * Autovacuum launcher wants stats about all databases, but a shallow read
-        * is sufficient.
+        * is sufficient.  Regular backends want a deep read for just the tables
+        * they can see (MyDatabaseId + shared catalogs).
         */
        if (IsAutoVacuumLauncherProcess())
                pgStatDBHash = pgstat_read_statsfiles(InvalidOid, false, false);
@@ -4495,9 +5694,7 @@ pgstat_setup_memcxt(void)
        if (!pgStatLocalContext)
                pgStatLocalContext = AllocSetContextCreate(TopMemoryContext,
                                                                                                   "Statistics snapshot",
-                                                                                                  ALLOCSET_SMALL_MINSIZE,
-                                                                                                  ALLOCSET_SMALL_INITSIZE,
-                                                                                                  ALLOCSET_SMALL_MAXSIZE);
+                                                                                                  ALLOCSET_SMALL_SIZES);
 }
 
 
@@ -4535,43 +5732,27 @@ pgstat_clear_snapshot(void)
 static void
 pgstat_recv_inquiry(PgStat_MsgInquiry *msg, int len)
 {
-       slist_iter      iter;
-       DBWriteRequest *newreq;
        PgStat_StatDBEntry *dbentry;
 
-       elog(DEBUG2, "received inquiry for %d", msg->databaseid);
+       elog(DEBUG2, "received inquiry for database %u", msg->databaseid);
 
        /*
-        * Find the last write request for this DB.  If it's older than the
-        * request's cutoff time, update it; otherwise there's nothing to do.
+        * If there's already a write request for this DB, there's nothing to do.
         *
         * Note that if a request is found, we return early and skip the below
         * check for clock skew.  This is okay, since the only way for a DB
         * request to be present in the list is that we have been here since the
-        * last write round.
+        * last write round.  It seems sufficient to check for clock skew once per
+        * write round.
         */
-       slist_foreach(iter, &last_statrequests)
-       {
-               DBWriteRequest *req = slist_container(DBWriteRequest, next, iter.cur);
-
-               if (req->databaseid != msg->databaseid)
-                       continue;
-
-               if (msg->cutoff_time > req->request_time)
-                       req->request_time = msg->cutoff_time;
+       if (list_member_oid(pending_write_requests, msg->databaseid))
                return;
-       }
-
-       /*
-        * There's no request for this DB yet, so create one.
-        */
-       newreq = palloc(sizeof(DBWriteRequest));
-
-       newreq->databaseid = msg->databaseid;
-       newreq->request_time = msg->clock_time;
-       slist_push_head(&last_statrequests, &newreq->next);
 
        /*
+        * Check to see if we last wrote this database at a time >= the requested
+        * cutoff time.  If so, this is a stale request that was generated before
+        * we updated the DB file, and we don't need to do so again.
+        *
         * If the requestor's local clock time is older than stats_timestamp, we
         * should suspect a clock glitch, ie system time going backwards; though
         * the more likely explanation is just delayed message receipt.  It is
@@ -4580,7 +5761,17 @@ pgstat_recv_inquiry(PgStat_MsgInquiry *msg, int len)
         * to update the stats file for a long time.
         */
        dbentry = pgstat_get_db_entry(msg->databaseid, false);
-       if ((dbentry != NULL) && (msg->clock_time < dbentry->stats_timestamp))
+       if (dbentry == NULL)
+       {
+               /*
+                * We have no data for this DB.  Enter a write request anyway so that
+                * the global stats will get updated.  This is needed to prevent
+                * backend_read_statsfile from waiting for data that we cannot supply,
+                * in the case of a new DB that nobody has yet reported any stats for.
+                * See the behavior of pgstat_read_db_statsfile_timestamp.
+                */
+       }
+       else if (msg->clock_time < dbentry->stats_timestamp)
        {
                TimestampTz cur_ts = GetCurrentTimestamp();
 
@@ -4597,15 +5788,31 @@ pgstat_recv_inquiry(PgStat_MsgInquiry *msg, int len)
                        writetime = pstrdup(timestamptz_to_str(dbentry->stats_timestamp));
                        mytime = pstrdup(timestamptz_to_str(cur_ts));
                        elog(LOG,
-                       "stats_timestamp %s is later than collector's time %s for db %d",
+                                "stats_timestamp %s is later than collector's time %s for database %u",
                                 writetime, mytime, dbentry->databaseid);
                        pfree(writetime);
                        pfree(mytime);
-
-                       newreq->request_time = cur_ts;
-                       dbentry->stats_timestamp = cur_ts - 1;
+               }
+               else
+               {
+                       /*
+                        * Nope, it's just an old request.  Assuming msg's clock_time is
+                        * >= its cutoff_time, it must be stale, so we can ignore it.
+                        */
+                       return;
                }
        }
+       else if (msg->cutoff_time <= dbentry->stats_timestamp)
+       {
+               /* Stale request, ignore it */
+               return;
+       }
+
+       /*
+        * We need to write this DB, so create a request.
+        */
+       pending_write_requests = lappend_oid(pending_write_requests,
+                                                                                msg->databaseid);
 }
 
 
@@ -4641,7 +5848,7 @@ pgstat_recv_tabstat(PgStat_MsgTabstat *msg, int len)
                PgStat_TableEntry *tabmsg = &(msg->m_entry[i]);
 
                tabentry = (PgStat_StatTabEntry *) hash_search(dbentry->tables,
-                                                                                                       (void *) &(tabmsg->t_id),
+                                                                                                          (void *) &(tabmsg->t_id),
                                                                                                           HASH_ENTER, &found);
 
                if (!found)
@@ -4684,6 +5891,12 @@ pgstat_recv_tabstat(PgStat_MsgTabstat *msg, int len)
                        tabentry->tuples_updated += tabmsg->t_counts.t_tuples_updated;
                        tabentry->tuples_deleted += tabmsg->t_counts.t_tuples_deleted;
                        tabentry->tuples_hot_updated += tabmsg->t_counts.t_tuples_hot_updated;
+                       /* If table was truncated, first reset the live/dead counters */
+                       if (tabmsg->t_counts.t_truncated)
+                       {
+                               tabentry->n_live_tuples = 0;
+                               tabentry->n_dead_tuples = 0;
+                       }
                        tabentry->n_live_tuples += tabmsg->t_counts.t_delta_live_tuples;
                        tabentry->n_dead_tuples += tabmsg->t_counts.t_delta_dead_tuples;
                        tabentry->changes_since_analyze += tabmsg->t_counts.t_changed_tuples;
@@ -4769,7 +5982,7 @@ pgstat_recv_dropdb(PgStat_MsgDropdb *msg, int len)
 
                get_dbstat_filename(false, false, dbid, statfile, MAXPGPATH);
 
-               elog(DEBUG2, "removing %s", statfile);
+               elog(DEBUG2, "removing stats file \"%s\"", statfile);
                unlink(statfile);
 
                if (dbentry->tables != NULL)
@@ -4956,10 +6169,12 @@ pgstat_recv_analyze(PgStat_MsgAnalyze *msg, int len)
        tabentry->n_dead_tuples = msg->m_dead_tuples;
 
        /*
-        * We reset changes_since_analyze to zero, forgetting any changes that
-        * occurred while the ANALYZE was in progress.
+        * If commanded, reset changes_since_analyze to zero.  This forgets any
+        * changes that were committed while the ANALYZE was in progress, but we
+        * have no good way to estimate how many of those there were.
         */
-       tabentry->changes_since_analyze = 0;
+       if (msg->m_resetcounter)
+               tabentry->changes_since_analyze = 0;
 
        if (msg->m_autovacuum)
        {
@@ -5078,6 +6293,22 @@ pgstat_recv_deadlock(PgStat_MsgDeadlock *msg, int len)
        dbentry->n_deadlocks++;
 }
 
+/* ----------
+ * pgstat_recv_checksum_failure() -
+ *
+ *     Process a CHECKSUMFAILURE message.
+ * ----------
+ */
+static void
+pgstat_recv_checksum_failure(PgStat_MsgChecksumFailure *msg, int len)
+{
+       PgStat_StatDBEntry *dbentry;
+
+       dbentry = pgstat_get_db_entry(msg->m_databaseid, true);
+
+       dbentry->n_checksum_failures += msg->m_failurecount;
+}
+
 /* ----------
  * pgstat_recv_tempfile() -
  *
@@ -5118,7 +6349,7 @@ pgstat_recv_funcstat(PgStat_MsgFuncstat *msg, int len)
        for (i = 0; i < msg->m_nentries; i++, funcmsg++)
        {
                funcentry = (PgStat_StatFuncEntry *) hash_search(dbentry->functions,
-                                                                                                  (void *) &(funcmsg->f_id),
+                                                                                                                (void *) &(funcmsg->f_id),
                                                                                                                 HASH_ENTER, &found);
 
                if (!found)
@@ -5178,13 +6409,13 @@ pgstat_recv_funcpurge(PgStat_MsgFuncpurge *msg, int len)
 /* ----------
  * pgstat_write_statsfile_needed() -
  *
- *     Do we need to write out the files?
+ *     Do we need to write out any stats files?
  * ----------
  */
 static bool
 pgstat_write_statsfile_needed(void)
 {
-       if (!slist_is_empty(&last_statrequests))
+       if (pending_write_requests != NIL)
                return true;
 
        /* Everything was written recently */
@@ -5200,16 +6431,62 @@ pgstat_write_statsfile_needed(void)
 static bool
 pgstat_db_requested(Oid databaseid)
 {
-       slist_iter      iter;
-
-       /* Check the databases if they need to refresh the stats. */
-       slist_foreach(iter, &last_statrequests)
-       {
-               DBWriteRequest *req = slist_container(DBWriteRequest, next, iter.cur);
+       /*
+        * If any requests are outstanding at all, we should write the stats for
+        * shared catalogs (the "database" with OID 0).  This ensures that
+        * backends will see up-to-date stats for shared catalogs, even though
+        * they send inquiry messages mentioning only their own DB.
+        */
+       if (databaseid == InvalidOid && pending_write_requests != NIL)
+               return true;
 
-               if (req->databaseid == databaseid)
-                       return true;
-       }
+       /* Search to see if there's an open request to write this database. */
+       if (list_member_oid(pending_write_requests, databaseid))
+               return true;
 
        return false;
 }
+
+/*
+ * Convert a potentially unsafely truncated activity string (see
+ * PgBackendStatus.st_activity_raw's documentation) into a correctly truncated
+ * one.
+ *
+ * The returned string is allocated in the caller's memory context and may be
+ * freed.
+ */
+char *
+pgstat_clip_activity(const char *raw_activity)
+{
+       char       *activity;
+       int                     rawlen;
+       int                     cliplen;
+
+       /*
+        * Some callers, like pgstat_get_backend_current_activity(), do not
+        * guarantee that the buffer isn't concurrently modified. We try to take
+        * care that the buffer is always terminated by a NUL byte regardless, but
+        * let's still be paranoid about the string's length. In those cases the
+        * underlying buffer is guaranteed to be pgstat_track_activity_query_size
+        * large.
+        */
+       activity = pnstrdup(raw_activity, pgstat_track_activity_query_size - 1);
+
+       /* now double-guaranteed to be NUL terminated */
+       rawlen = strlen(activity);
+
+       /*
+        * All supported server-encodings make it possible to determine the length
+        * of a multi-byte character from its first byte (this is not the case for
+        * client encodings, see GB18030). As st_activity is always stored using
+        * server encoding, this allows us to perform multi-byte aware truncation,
+        * even if the string earlier was truncated in the middle of a multi-byte
+        * character.
+        */
+       cliplen = pg_mbcliplen(activity, rawlen,
+                                                  pgstat_track_activity_query_size - 1);
+
+       activity[cliplen] = '\0';
+
+       return activity;
+}