<!--
-$Header: /cvsroot/pgsql/doc/src/sgml/monitoring.sgml,v 1.10 2002/08/04 19:51:30 momjian Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/monitoring.sgml,v 1.11 2002/08/17 13:04:14 momjian Exp $
-->
<chapter id="monitoring">
</sect2>
</sect1>
+
+ <sect1 id="monitoring-locks">
+ <title>Viewing Locks</title>
+
+ <para>
+ Another useful tool for monitoring database activity is the
+ <literal>pg_locks</literal> system catalog. This allows the
+ database administrator to view information about the outstanding
+ locks in the lock manager. For example, this capability can be
+ used to:
+ <itemizedlist>
+ <listitem>
+ <para>
+ View all the locks currently outstanding, all the locks on
+ relations in a particular database, all the locks on a
+ particular relation, or all the locks held by a particular
+ <productname>PostgreSQL</productname> backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ View the relation in the current database with the most
+ un-granted locks (which might be a source of contention among
+ database clients).
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ Determine the effect of lock contention on overall database
+ performance, as well as the extent to which contention varies
+ with overall database traffic.
+ </para>
+ </listitem>
+ </itemizedlist>
+
+ For more information on locking and managing concurrency with
+ <productname>PostgreSQL</productname>, refer to the
+ <citetitle>Administrator's Guide</citetitle>.
+ </para>
+
+ <note>
+ <para>
+ When the <literal>pg_locks</literal> view is accessed, an
+ exclusive lock on an internal lock manager data structure must be
+ acquired to ensure that the data produced by the view is
+ consistent. The lock held on this structure conflicts with normal
+ database operations, and can therefore have an effect on overall
+ database performance. Nevertheless, the performance impact of
+ accessing this view should be minimal in most situations.
+ </para>
+ </note>
+
+ <para>
+ The <literal>pg_locks</literal> view contains one row per
+ lock. This means that if there are multiple locks on a single
+ relation (which may or may not conflict with one another), a
+ single relation may show up many times. Furthermore, only
+ table-level locks are displayed (not row-level ones).
+ </para>
+
+ <table>
+ <title>Lock Status System View</title>
+
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Column Name</entry>
+ <entry>Type</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry><structfield>relation</structfield></entry>
+ <entry><type>oid</type></entry>
+ <entry>The OID of the locked relation. When querying
+ <literal>pg_locks</literal>, this column can be joined with the
+ <literal>pg_class</literal> system catalog to get more
+ information on the locked relation.</entry>
+ </row>
+
+ <row>
+ <entry><structfield>database</structfield></entry>
+ <entry><type>oid</type></entry>
+ <entry>The OID of the database in which the locked relation
+ exists. If the lock is on a globally-shared object, this value
+ will be 0. When querying <literal>pg_locks</literal>, this
+ column can be joined with the <literal>pg_database</literal>
+ system catalog to get more information on the locked object's
+ database.</entry>
+ </row>
+
+ <row>
+ <entry><structfield>backendpid</structfield></entry>
+ <entry><type>int4</type></entry>
+ <entry>The process ID of the
+ <productname>PostgreSQL</productname> backend that has
+ acquired or is attempting to acquire the lock. If you have
+ enabled the statistics collector, this column can be joined
+ with the <literal>pg_stat_activity</literal> view to access
+ more information on the backend holding or waiting to hold the
+ lock.</entry>
+ </row>
+
+ <row>
+ <entry><structfield>mode</structfield></entry>
+ <entry><type>text</type></entry>
+ <entry>The mode of the lock. For more information on the
+ different lock modes available in
+ <productname>PostgreSQL</productname>, refer to the
+ <citetitle>User's Guide</citetitle>.</entry>
+ </row>
+
+ <row>
+ <entry><structfield>isgranted</structfield></entry>
+ <entry><type>text</type></entry>
+ <entry>A boolean column indicating whether or not this
+ particular lock has been granted. If the lock has not been
+ granted, the backend atempting to acquire it will sleep until
+ the lock is released (or a deadlock situation is detected). A
+ single backend can be waiting to acquire at most one lock at
+ any given time.</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+ </sect1>
</chapter>
<!-- Keep this comment at the end of the file
<!--
-$Header: /cvsroot/pgsql/doc/src/sgml/mvcc.sgml,v 2.26 2002/08/05 19:43:31 petere Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/mvcc.sgml,v 2.27 2002/08/17 13:04:14 momjian Exp $
-->
<chapter id="mvcc">
modes on the same table at the same time. (However, a transaction
never conflicts with itself --- for example, it may acquire
<literal>ACCESS EXCLUSIVE</literal> lock and later acquire
- <literal>ACCESS SHARE</literal> lock on the same table.) Nonconflicting
+ <literal>ACCESS SHARE</literal> lock on the same table.) Non-conflicting
lock modes may be held concurrently by many transactions. Notice in
particular that some lock modes are self-conflicting (for example,
<literal>ACCESS EXCLUSIVE</literal> cannot be held by more than one
Once acquired, a lock mode is held till end of transaction.
</para>
+ <para>
+ To examine a list of the currently outstanding locks in a
+ database server, use the <literal>pg_locks</literal> system
+ view. For more information on monitoring the status of the lock
+ manager subsystem, refer to the <citetitle>Administrator's
+ Guide</citetitle>.
+ </para>
+
<variablelist>
<title>Table-level lock modes</title>
<varlistentry>
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/storage/lmgr/lock.c,v 1.111 2002/08/01 05:18:33 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/storage/lmgr/lock.c,v 1.112 2002/08/17 13:04:14 momjian Exp $
*
* NOTES
* Outside modules can create a lock table and acquire/release
return size;
}
+/*
+ * GetLockStatusData - Return a summary of the lock manager's internal
+ * status, for use in a user-level statistical reporting function.
+ *
+ * This function should be passed a pointer to a LockData struct. It fills
+ * the structure with the appropriate information and returns. The goal
+ * is to hold the LockMgrLock for as short a time as possible; thus, the
+ * function simply makes a copy of the necessary data and releases the
+ * lock, allowing the caller to contemplate and format the data for
+ * as long as it pleases.
+ */
+void
+GetLockStatusData(LockData *data)
+{
+ HTAB *holderTable;
+ PROCLOCK *holder;
+ HASH_SEQ_STATUS seqstat;
+ int i = 0;
+
+ data->currIdx = 0;
+
+ LWLockAcquire(LockMgrLock, LW_EXCLUSIVE);
+
+ holderTable = LockMethodTable[DEFAULT_LOCKMETHOD]->holderHash;
+
+ data->nelements = holderTable->hctl->nentries;
+
+ data->procs = (PGPROC *) palloc(sizeof(PGPROC) * data->nelements);
+ data->locks = (LOCK *) palloc(sizeof(LOCK) * data->nelements);
+ data->holders = (PROCLOCK *) palloc(sizeof(PROCLOCK) * data->nelements);
+
+ hash_seq_init(&seqstat, holderTable);
+
+ while ( (holder = hash_seq_search(&seqstat)) )
+ {
+ PGPROC *proc;
+ LOCK *lock;
+
+ /* Only do a shallow copy */
+ proc = (PGPROC *) MAKE_PTR(holder->tag.proc);
+ lock = (LOCK *) MAKE_PTR(holder->tag.lock);
+
+ memcpy(&(data->procs[i]), proc, sizeof(PGPROC));
+ memcpy(&(data->locks[i]), lock, sizeof(LOCK));
+ memcpy(&(data->holders[i]), holder, sizeof(PROCLOCK));
+
+ i++;
+ }
+
+ Assert(i == data->nelements);
+
+ LWLockRelease(LockMgrLock);
+}
+
+char *
+GetLockmodeName(LOCKMODE mode)
+{
+ Assert(mode <= MAX_LOCKMODES);
+ return lock_mode_names[mode];
+}
#ifdef LOCK_DEBUG
/*
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/tcop/utility.c,v 1.171 2002/08/17 12:15:49 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/tcop/utility.c,v 1.172 2002/08/17 13:04:15 momjian Exp $
*
*-------------------------------------------------------------------------
*/
break;
/*
- * ******************************** portal manipulation ********************************
- *
+ * ************************* portal manipulation ***************************
*/
case T_ClosePortalStmt:
{
#
# Makefile for utils/adt
#
-# $Header: /cvsroot/pgsql/src/backend/utils/adt/Makefile,v 1.51 2001/10/04 04:13:40 ishii Exp $
+# $Header: /cvsroot/pgsql/src/backend/utils/adt/Makefile,v 1.52 2002/08/17 13:04:15 momjian Exp $
#
subdir = src/backend/utils/adt
OBJS = acl.o arrayfuncs.o arrayutils.o bool.o cash.o char.o \
date.o datetime.o datum.o float.o format_type.o \
- geo_ops.o geo_selfuncs.o int.o int8.o like.o \
+ geo_ops.o geo_selfuncs.o int.o int8.o like.o lockfuncs.o \
misc.o nabstime.o name.o not_in.o numeric.o numutils.o \
oid.o oracle_compat.o \
regexp.o regproc.o ruleutils.o selfuncs.o sets.o \
# Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
# Portions Copyright (c) 1994, Regents of the University of California
#
-# $Header: /cvsroot/pgsql/src/bin/initdb/Attic/initdb.sh,v 1.166 2002/08/15 02:51:26 momjian Exp $
+# $Header: /cvsroot/pgsql/src/bin/initdb/Attic/initdb.sh,v 1.167 2002/08/17 13:04:15 momjian Exp $
#
#-------------------------------------------------------------------------
FROM pg_class C LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace) \
WHERE C.relkind = 'v';
--- XXX why does pg_tables include sequences?
-
CREATE VIEW pg_tables AS \
SELECT \
N.nspname AS schemaname, \
pg_stat_get_db_blocks_hit(D.oid) AS blks_hit \
FROM pg_database D;
+CREATE VIEW pg_locks_result AS \
+ SELECT \
+ ''::oid AS relation, \
+ ''::oid AS database, \
+ ''::int4 AS backendpid, \
+ ''::text AS mode, \
+ NULL::bool AS isgranted;
+
+UPDATE pg_proc SET \
+ prorettype = (SELECT oid FROM pg_type \
+ WHERE typname = 'pg_locks_result') \
+ WHERE proname = 'pg_lock_status';
+
+CREATE VIEW pg_locks AS SELECT * FROM pg_lock_status();
+
CREATE VIEW pg_settings AS \
SELECT \
A.name, \
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $Id: catversion.h,v 1.149 2002/08/16 23:01:20 tgl Exp $
+ * $Id: catversion.h,v 1.150 2002/08/17 13:04:15 momjian Exp $
*
*-------------------------------------------------------------------------
*/
*/
/* yyyymmddN */
-#define CATALOG_VERSION_NO 200208161
+#define CATALOG_VERSION_NO 200208171
#endif
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $Id: pg_proc.h,v 1.255 2002/08/16 23:01:20 tgl Exp $
+ * $Id: pg_proc.h,v 1.256 2002/08/17 13:04:15 momjian Exp $
*
* NOTES
* The script catalog/genbki.sh reads this file and generates .bki
DATA(insert OID = 1915 ( numeric_uplus PGNSP PGUID 12 f f t f i 1 1700 "1700" numeric_uplus - _null_ ));
DESCR("unary plus");
+DATA(insert OID = 1920 ( pg_lock_status PGNSP PGUID 12 f f f t v 0 0 "0" lock_status_srf - _null_ ));
+DESCR("view system lock information");
DATA(insert OID = 1922 ( has_table_privilege PGNSP PGUID 12 f f t f s 3 16 "19 25 25" has_table_privilege_name_name - _null_ ));
DESCR("user privilege on relation by username, rel name");
DATA(insert OID = 1923 ( has_table_privilege PGNSP PGUID 12 f f t f s 3 16 "19 26 25" has_table_privilege_name_id - _null_ ));
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $Id: lock.h,v 1.64 2002/08/01 05:18:34 momjian Exp $
+ * $Id: lock.h,v 1.65 2002/08/17 13:04:18 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#define PROCLOCK_LOCKMETHOD(holder) \
(((LOCK *) MAKE_PTR((holder).tag.lock))->tag.lockmethod)
+/*
+ * This struct is used to encapsulate information passed from lmgr
+ * internals to the lock listing statistical functions (lockfuncs.c).
+ * It's just a convenient bundle of other lock.h structures. All
+ * the information at a given index (holders[i], procs[i], locks[i])
+ * is related.
+ */
+typedef struct
+{
+ int nelements; /* The length of holders, procs, & locks */
+ int currIdx; /* Current element being examined */
+ PGPROC *procs;
+ LOCK *locks;
+ PROCLOCK *holders;
+} LockData;
/*
* function prototypes
extern int LockShmemSize(int maxBackends);
extern bool DeadLockCheck(PGPROC *proc);
extern void InitDeadLockChecking(void);
+extern void GetLockStatusData(LockData *data);
+extern char *GetLockmodeName(LOCKMODE mode);
#ifdef LOCK_DEBUG
extern void DumpLocks(void);
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $Id: shmem.h,v 1.37 2002/06/20 20:29:52 momjian Exp $
+ * $Id: shmem.h,v 1.38 2002/08/17 13:04:19 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#define SHM_OFFSET_VALID(xx_offs)\
(((xx_offs) != 0) && ((xx_offs) != INVALID_OFFSET))
-
-/* shmemqueue.c */
+/* shmqueue.c */
typedef struct SHM_QUEUE
{
SHMEM_OFFSET prev;
--------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
iexit | SELECT ih.name, ih.thepath, interpt_pp(ih.thepath, r.thepath) AS exit FROM ihighway ih, ramp r WHERE (ih.thepath ## r.thepath);
pg_indexes | SELECT n.nspname AS schemaname, c.relname AS tablename, i.relname AS indexname, pg_get_indexdef(i.oid) AS indexdef FROM (((pg_index x JOIN pg_class c ON ((c.oid = x.indrelid))) JOIN pg_class i ON ((i.oid = x.indexrelid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE ((c.relkind = 'r'::"char") AND (i.relkind = 'i'::"char"));
+ pg_locks | SELECT pg_lock_status.relation, pg_lock_status."database", pg_lock_status.backendpid, pg_lock_status."mode", pg_lock_status.isgranted FROM pg_lock_status();
+ pg_locks_result | SELECT 0::oid AS relation, 0::oid AS "database", 0 AS backendpid, ''::text AS "mode", NULL::boolean AS isgranted;
pg_rules | SELECT n.nspname AS schemaname, c.relname AS tablename, r.rulename, pg_get_ruledef(r.oid) AS definition FROM ((pg_rewrite r JOIN pg_class c ON ((c.oid = r.ev_class))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (r.rulename <> '_RETURN'::name);
pg_settings | SELECT a.name, a.setting FROM pg_show_all_settings() a;
pg_stat_activity | SELECT d.oid AS datid, d.datname, pg_stat_get_backend_pid(s.backendid) AS procpid, pg_stat_get_backend_userid(s.backendid) AS usesysid, u.usename, pg_stat_get_backend_activity(s.backendid) AS current_query FROM pg_database d, (SELECT pg_stat_get_backend_idset() AS backendid) s, pg_shadow u WHERE ((pg_stat_get_backend_dbid(s.backendid) = d.oid) AND (pg_stat_get_backend_userid(s.backendid) = u.usesysid));
shoelace_obsolete | SELECT shoelace.sl_name, shoelace.sl_avail, shoelace.sl_color, shoelace.sl_len, shoelace.sl_unit, shoelace.sl_len_cm FROM shoelace WHERE (NOT (EXISTS (SELECT shoe.shoename FROM shoe WHERE (shoe.slcolor = shoelace.sl_color))));
street | SELECT r.name, r.thepath, c.cname FROM ONLY road r, real_city c WHERE (c.outline ## r.thepath);
toyemp | SELECT emp.name, emp.age, emp."location", (12 * emp.salary) AS annualsal FROM emp;
-(39 rows)
+(41 rows)
SELECT tablename, rulename, definition FROM pg_rules
ORDER BY tablename, rulename;
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