Improve the performance of relation deletes during recovery.

When multiple relations are deleted at the same transaction,
the files of those relations are deleted by one call to smgrdounlinkall(),
which leads to scan whole shared_buffers only one time. OTOH,
previously, during recovery, smgrdounlink() (not smgrdounlinkall()) was
called for each file to delete, which led to scan shared_buffers
multiple times. Obviously this could cause to increase the WAL replay
time very much especially when shared_buffers was huge.

To alleviate this situation, this commit changes the recovery so that
it also calls smgrdounlinkall() only one time to delete multiple
relation files.

This is just fix for oversight of commit 279628a0a7, not new feature.
So, per discussion on pgsql-hackers, we concluded to backpatch this
to all supported versions.

Author: Fujii Masao
Reviewed-by: Michael Paquier, Andres Freund, Thomas Munro, Kyotaro Horiguchi, Takayuki Tsunakawa
Discussion: https://postgr.es/m/CAHGQGwHVQkdfDqtvGVkty+19cQakAydXn1etGND3X0PHbZ3+6w@mail.gmail.com

diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 10d615068ce6b91d7d7ea1996ccb764aa008e657..faf590b7709e618ff679e3807614d77eb45d6269 100644 (file)
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1373,7 +1373,6 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
        RelFileNode *delrels;
        int                     ndelrels;
        SharedInvalidationMessage *invalmsgs;
-       int                     i;
 
        /*
         * Validate the GID, and lock the GXACT to ensure that two backends do not
@@ -1463,13 +1462,9 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
                delrels = abortrels;
                ndelrels = hdr->nabortrels;
        }
-       for (i = 0; i < ndelrels; i++)
-       {
-               SMgrRelation srel = smgropen(delrels[i], InvalidBackendId);
 
-               smgrdounlink(srel, false);
-               smgrclose(srel);
-       }
+       /* Make sure files supposed to be dropped are dropped */
+       DropRelationFiles(delrels, ndelrels, false);
 
        /*
         * Handle cache invalidation messages.

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index f4ddd2604f8b7c46c4e773ed78b662bc343cb9ff..d3632c25cae2c1d72ecf2f78b8998205b00b397b 100644 (file)
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -5322,7 +5322,6 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
                                 RepOriginId origin_id)
 {
        TransactionId max_xid;
-       int                     i;
        TimestampTz commit_time;
 
        max_xid = TransactionIdLatest(xid, parsed->nsubxacts, parsed->subxacts);
@@ -5439,16 +5438,8 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
                 */
                XLogFlush(lsn);
 
-               for (i = 0; i < parsed->nrels; i++)
-               {
-                       SMgrRelation srel = smgropen(parsed->xnodes[i], InvalidBackendId);
-                       ForkNumber      fork;
-
-                       for (fork = 0; fork <= MAX_FORKNUM; fork++)
-                               XLogDropRelation(parsed->xnodes[i], fork);
-                       smgrdounlink(srel, true);
-                       smgrclose(srel);
-               }
+               /* Make sure files supposed to be dropped are dropped */
+               DropRelationFiles(parsed->xnodes, parsed->nrels, true);
        }
 
        /*
@@ -5480,7 +5471,6 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 static void
 xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)
 {
-       int                     i;
        TransactionId max_xid;
 
        /*
@@ -5542,16 +5532,7 @@ xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)
        }
 
        /* Make sure files supposed to be dropped are dropped */
-       for (i = 0; i < parsed->nrels; i++)
-       {
-               SMgrRelation srel = smgropen(parsed->xnodes[i], InvalidBackendId);
-               ForkNumber      fork;
-
-               for (fork = 0; fork <= MAX_FORKNUM; fork++)
-                       XLogDropRelation(parsed->xnodes[i], fork);
-               smgrdounlink(srel, true);
-               smgrclose(srel);
-       }
+       DropRelationFiles(parsed->xnodes, parsed->nrels, true);
 }
 
 void

diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c
index b36198ed4a8277bcfd43def6e495f57baaca303f..849055b191a36a9586f283f99a098e3330a2df96 100644 (file)
--- a/src/backend/storage/smgr/md.c
+++ b/src/backend/storage/smgr/md.c
@@ -26,6 +26,7 @@
 #include <sys/file.h>
 
 #include "miscadmin.h"
+#include "access/xlogutils.h"
 #include "access/xlog.h"
 #include "catalog/catalog.h"
 #include "portability/instr_time.h"
@@ -1641,6 +1642,43 @@ ForgetDatabaseFsyncRequests(Oid dbid)
        }
 }
 
+/*
+ * DropRelationFiles -- drop files of all given relations
+ */
+void
+DropRelationFiles(RelFileNode *delrels, int ndelrels, bool isRedo)
+{
+       SMgrRelation *srels;
+       int                     i;
+
+       srels = palloc(sizeof(SMgrRelation) * ndelrels);
+       for (i = 0; i < ndelrels; i++)
+       {
+               SMgrRelation srel = smgropen(delrels[i], InvalidBackendId);
+
+               if (isRedo)
+               {
+                       ForkNumber      fork;
+
+                       for (fork = 0; fork <= MAX_FORKNUM; fork++)
+                               XLogDropRelation(delrels[i], fork);
+               }
+               srels[i] = srel;
+       }
+
+       smgrdounlinkall(srels, ndelrels, isRedo);
+
+       /*
+        * Call smgrclose() in reverse order as when smgropen() is called.
+        * This trick enables remove_from_unowned_list() in smgrclose()
+        * to search the SMgrRelation from the unowned list,
+        * with O(1) performance.
+        */
+       for (i = ndelrels - 1; i >= 0; i--)
+               smgrclose(srels[i]);
+       pfree(srels);
+}
+
 
 /*
  *     _fdvec_alloc() -- Make a MdfdVec object.

diff --git a/src/include/storage/smgr.h b/src/include/storage/smgr.h
index 69a624fe237e5832394ca111e3facadccc04c511..dfb7e98e9328380bdc8cc08466a024cb9b9289a8 100644 (file)
--- a/src/include/storage/smgr.h
+++ b/src/include/storage/smgr.h
@@ -135,6 +135,7 @@ extern void RememberFsyncRequest(RelFileNode rnode, ForkNumber forknum,
                                         BlockNumber segno);
 extern void ForgetRelationFsyncRequests(RelFileNode rnode, ForkNumber forknum);
 extern void ForgetDatabaseFsyncRequests(Oid dbid);
+extern void DropRelationFiles(RelFileNode *delrels, int ndelrels, bool isRedo);
 
 /* smgrtype.c */
 extern Datum smgrout(PG_FUNCTION_ARGS);