From b56b6d8c8686e7dd2b77c25d3d9d61908b769878 Mon Sep 17 00:00:00 2001 From: jcoleman Date: Fri, 9 Jun 2023 20:12:31 -0500 Subject: [PATCH v2] Add last commit's LSN to pg_stat_database --- doc/src/sgml/monitoring.sgml | 9 ++++++++ src/backend/access/transam/twophase.c | 11 +++++---- src/backend/access/transam/xact.c | 11 +++++---- src/backend/catalog/system_views.sql | 1 + src/backend/utils/activity/pgstat_database.c | 20 +++++++++++++++- src/backend/utils/activity/pgstat_xact.c | 4 ++-- src/backend/utils/adt/pgstatfuncs.c | 3 +++ src/include/catalog/pg_proc.dat | 4 ++++ src/include/pgstat.h | 4 +++- src/include/utils/pgstat_internal.h | 2 +- src/test/regress/expected/rules.out | 1 + src/test/regress/expected/stats.out | 24 ++++++++++++++++++++ src/test/regress/sql/stats.sql | 10 ++++++++ 13 files changed, 90 insertions(+), 14 deletions(-) diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml index df5242fa80..6f2ea1ddbe 100644 --- a/doc/src/sgml/monitoring.sgml +++ b/doc/src/sgml/monitoring.sgml @@ -4414,6 +4414,15 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i + + + last_commit_lsn pg_lsn + + + Write-ahead log location of the last commit in this database + + + xact_commit bigint diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c index 068e59bec0..c38e36e37c 100644 --- a/src/backend/access/transam/twophase.c +++ b/src/backend/access/transam/twophase.c @@ -200,7 +200,7 @@ static GlobalTransaction MyLockedGxact = NULL; static bool twophaseExitRegistered = false; -static void RecordTransactionCommitPrepared(TransactionId xid, +static XLogRecPtr RecordTransactionCommitPrepared(TransactionId xid, int nchildren, TransactionId *children, int nrels, @@ -1494,6 +1494,7 @@ FinishPreparedTransaction(const char *gid, bool isCommit) xl_xact_stats_item *commitstats; xl_xact_stats_item *abortstats; SharedInvalidationMessage *invalmsgs; + XLogRecPtr commit_lsn = InvalidXLogRecPtr; /* * Validate the GID, and lock the GXACT to ensure that two backends do not @@ -1549,7 +1550,7 @@ FinishPreparedTransaction(const char *gid, bool isCommit) * callbacks will release the locks the transaction held. */ if (isCommit) - RecordTransactionCommitPrepared(xid, + commit_lsn = RecordTransactionCommitPrepared(xid, hdr->nsubxacts, children, hdr->ncommitrels, commitrels, hdr->ncommitstats, @@ -1644,7 +1645,7 @@ FinishPreparedTransaction(const char *gid, bool isCommit) LWLockRelease(TwoPhaseStateLock); /* Count the prepared xact as committed or aborted */ - AtEOXact_PgStat(isCommit, false); + AtEOXact_PgStat(isCommit, commit_lsn, false); /* * And now we can clean up any files we may have left. @@ -2278,7 +2279,7 @@ ProcessTwoPhaseBuffer(TransactionId xid, * We know the transaction made at least one XLOG entry (its PREPARE), * so it is never possible to optimize out the commit record. */ -static void +static XLogRecPtr RecordTransactionCommitPrepared(TransactionId xid, int nchildren, TransactionId *children, @@ -2366,6 +2367,8 @@ RecordTransactionCommitPrepared(TransactionId xid, * in the procarray and continue to hold locks. */ SyncRepWaitForLSN(recptr, true); + + return recptr; } /* diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c index 8daaa535ed..895e103c70 100644 --- a/src/backend/access/transam/xact.c +++ b/src/backend/access/transam/xact.c @@ -1280,7 +1280,7 @@ AtSubStart_ResourceOwner(void) * If you change this function, see RecordTransactionCommitPrepared also. */ static TransactionId -RecordTransactionCommit(void) +RecordTransactionCommit(XLogRecPtr *commit_lsn) { TransactionId xid = GetTopTransactionIdIfAny(); bool markXidCommitted = TransactionIdIsValid(xid); @@ -1397,7 +1397,7 @@ RecordTransactionCommit(void) /* * Insert the commit XLOG record. */ - XactLogCommitRecord(GetCurrentTransactionStopTimestamp(), + *commit_lsn = XactLogCommitRecord(GetCurrentTransactionStopTimestamp(), nchildren, children, nrels, rels, ndroppedstats, droppedstats, nmsgs, invalMessages, @@ -2153,6 +2153,7 @@ CommitTransaction(void) { TransactionState s = CurrentTransactionState; TransactionId latestXid; + XLogRecPtr commit_lsn = InvalidXLogRecPtr; bool is_parallel_worker; is_parallel_worker = (s->blockState == TBLOCK_PARALLEL_INPROGRESS); @@ -2264,7 +2265,7 @@ CommitTransaction(void) * We need to mark our XIDs as committed in pg_xact. This is where we * durably commit. */ - latestXid = RecordTransactionCommit(); + latestXid = RecordTransactionCommit(&commit_lsn); } else { @@ -2368,7 +2369,7 @@ CommitTransaction(void) AtEOXact_Files(true); AtEOXact_ComboCid(); AtEOXact_HashTables(true); - AtEOXact_PgStat(true, is_parallel_worker); + AtEOXact_PgStat(true, commit_lsn, is_parallel_worker); AtEOXact_Snapshot(true, false); AtEOXact_ApplyLauncher(true); AtEOXact_LogicalRepWorkers(true); @@ -2869,7 +2870,7 @@ AbortTransaction(void) AtEOXact_Files(false); AtEOXact_ComboCid(); AtEOXact_HashTables(false); - AtEOXact_PgStat(false, is_parallel_worker); + AtEOXact_PgStat(false, InvalidXLogRecPtr, is_parallel_worker); AtEOXact_ApplyLauncher(false); AtEOXact_LogicalRepWorkers(false); pgstat_report_xact_timestamp(0); diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql index c18fea8362..014d1d0433 100644 --- a/src/backend/catalog/system_views.sql +++ b/src/backend/catalog/system_views.sql @@ -1029,6 +1029,7 @@ CREATE VIEW pg_stat_database AS WHEN (D.oid = (0)::oid) THEN 0 ELSE pg_stat_get_db_numbackends(D.oid) END AS numbackends, + pg_stat_get_db_last_commit_lsn(D.oid) AS last_commit_lsn, pg_stat_get_db_xact_commit(D.oid) AS xact_commit, pg_stat_get_db_xact_rollback(D.oid) AS xact_rollback, pg_stat_get_db_blocks_fetched(D.oid) - diff --git a/src/backend/utils/activity/pgstat_database.c b/src/backend/utils/activity/pgstat_database.c index 7149f22f72..529cf0dee3 100644 --- a/src/backend/utils/activity/pgstat_database.c +++ b/src/backend/utils/activity/pgstat_database.c @@ -34,6 +34,7 @@ SessionEndType pgStatSessionEndCause = DISCONNECT_NORMAL; static int pgStatXactCommit = 0; static int pgStatXactRollback = 0; +static XLogRecPtr pgStatLastCommitLSN = InvalidXLogRecPtr; static PgStat_Counter pgLastSessionReportTime = 0; @@ -246,7 +247,7 @@ pgstat_fetch_stat_dbentry(Oid dboid) } void -AtEOXact_PgStat_Database(bool isCommit, bool parallel) +AtEOXact_PgStat_Database(bool isCommit, XLogRecPtr commit_lsn, bool parallel) { /* Don't count parallel worker transaction stats */ if (!parallel) @@ -256,7 +257,12 @@ AtEOXact_PgStat_Database(bool isCommit, bool parallel) * bools, in case the reporting message isn't sent right away.) */ if (isCommit) + { pgStatXactCommit++; + /* For commits also track the LSN of the commit record. */ + if (!XLogRecPtrIsInvalid(commit_lsn)) + pgStatLastCommitLSN = commit_lsn; + } else pgStatXactRollback++; } @@ -273,6 +279,13 @@ pgstat_update_dbstats(TimestampTz ts) dbentry = pgstat_prep_database_pending(MyDatabaseId); + /* + * pgStatLastCommitLSN is only ever set when there's a valid commit, so we + * know the LSN must be valid, and since we're local to the current backend + * we don't have to worry if we're advancing or not. + */ + dbentry->last_commit_lsn = pgStatLastCommitLSN; + /* * Accumulate xact commit/rollback and I/O timings to stats entry of the * current database. @@ -304,6 +317,7 @@ pgstat_update_dbstats(TimestampTz ts) pgStatBlockWriteTime = 0; pgStatActiveTime = 0; pgStatTransactionIdleTime = 0; + /* No reason to zero out pgStatLastCommitLSN; it's not accumulative. */ } /* @@ -414,6 +428,10 @@ pgstat_database_flush_cb(PgStat_EntryRef *entry_ref, bool nowait) PGSTAT_ACCUM_DBCOUNT(sessions_killed); #undef PGSTAT_ACCUM_DBCOUNT + /* Only update last_commit_lsn if our backend has the newest commit. */ + if (pendingent->last_commit_lsn > sharedent->stats.last_commit_lsn) + sharedent->stats.last_commit_lsn = pendingent->last_commit_lsn; + pgstat_unlock_entry(entry_ref); memset(pendingent, 0, sizeof(*pendingent)); diff --git a/src/backend/utils/activity/pgstat_xact.c b/src/backend/utils/activity/pgstat_xact.c index 369239d501..2713b6a4e6 100644 --- a/src/backend/utils/activity/pgstat_xact.c +++ b/src/backend/utils/activity/pgstat_xact.c @@ -38,11 +38,11 @@ static PgStat_SubXactStatus *pgStatXactStack = NULL; * Called from access/transam/xact.c at top-level transaction commit/abort. */ void -AtEOXact_PgStat(bool isCommit, bool parallel) +AtEOXact_PgStat(bool isCommit, XLogRecPtr commit_lsn, bool parallel) { PgStat_SubXactStatus *xact_state; - AtEOXact_PgStat_Database(isCommit, parallel); + AtEOXact_PgStat_Database(isCommit, commit_lsn, parallel); /* handle transactional stats information */ xact_state = pgStatXactStack; diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c index 49adc319fc..d1a4222458 100644 --- a/src/backend/utils/adt/pgstatfuncs.c +++ b/src/backend/utils/adt/pgstatfuncs.c @@ -1065,6 +1065,9 @@ PG_STAT_GET_DBENTRY_INT64(tuples_returned) /* pg_stat_get_db_tuples_updated */ PG_STAT_GET_DBENTRY_INT64(tuples_updated) +/* pg_stat_get_db_last_commit_lsn */ +PG_STAT_GET_DBENTRY_INT64(last_commit_lsn) + /* pg_stat_get_db_xact_commit */ PG_STAT_GET_DBENTRY_INT64(xact_commit) diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat index 6996073989..377a0a6ae0 100644 --- a/src/include/catalog/pg_proc.dat +++ b/src/include/catalog/pg_proc.dat @@ -5534,6 +5534,10 @@ proname => 'pg_stat_get_db_numbackends', provolatile => 's', proparallel => 'r', prorettype => 'int4', proargtypes => 'oid', prosrc => 'pg_stat_get_db_numbackends' }, +{ oid => '8000', descr => 'statistics: wal location of last committed transaction', + proname => 'pg_stat_get_db_last_commit_lsn', provolatile => 's', + proparallel => 'r', prorettype => 'pg_lsn', proargtypes => 'oid', + prosrc => 'pg_stat_get_db_last_commit_lsn' }, { oid => '1942', descr => 'statistics: transactions committed', proname => 'pg_stat_get_db_xact_commit', provolatile => 's', proparallel => 'r', prorettype => 'int8', proargtypes => 'oid', diff --git a/src/include/pgstat.h b/src/include/pgstat.h index 57a2c0866a..c492759a71 100644 --- a/src/include/pgstat.h +++ b/src/include/pgstat.h @@ -18,6 +18,7 @@ #include "utils/backend_status.h" /* for backward compatibility */ #include "utils/relcache.h" #include "utils/wait_event.h" /* for backward compatibility */ +#include "access/xlogdefs.h" /* ---------- @@ -320,6 +321,7 @@ typedef struct PgStat_IO typedef struct PgStat_StatDBEntry { + XLogRecPtr last_commit_lsn; PgStat_Counter xact_commit; PgStat_Counter xact_rollback; PgStat_Counter blocks_fetched; @@ -702,7 +704,7 @@ extern PgStat_StatSubEntry *pgstat_fetch_stat_subscription(Oid subid); * Functions in pgstat_xact.c */ -extern void AtEOXact_PgStat(bool isCommit, bool parallel); +extern void AtEOXact_PgStat(bool isCommit, XLogRecPtr commit_lsn, bool parallel); extern void AtEOSubXact_PgStat(bool isCommit, int nestDepth); extern void AtPrepare_PgStat(void); extern void PostPrepare_PgStat(void); diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h index 60fbf9394b..700d9c27bb 100644 --- a/src/include/utils/pgstat_internal.h +++ b/src/include/utils/pgstat_internal.h @@ -548,7 +548,7 @@ extern void pgstat_checkpointer_snapshot_cb(void); extern void pgstat_report_disconnect(Oid dboid); extern void pgstat_update_dbstats(TimestampTz ts); -extern void AtEOXact_PgStat_Database(bool isCommit, bool parallel); +extern void AtEOXact_PgStat_Database(bool isCommit, XLogRecPtr commit_lsn, bool parallel); extern PgStat_StatDBEntry *pgstat_prep_database_pending(Oid dboid); extern void pgstat_reset_database_timestamp(Oid dboid, TimestampTz ts); diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out index 7fd81e6a7d..62b909ca92 100644 --- a/src/test/regress/expected/rules.out +++ b/src/test/regress/expected/rules.out @@ -1833,6 +1833,7 @@ pg_stat_database| SELECT oid AS datid, WHEN (oid = (0)::oid) THEN 0 ELSE pg_stat_get_db_numbackends(oid) END AS numbackends, + pg_stat_get_db_last_commit_lsn(oid) AS last_commit_lsn, pg_stat_get_db_xact_commit(oid) AS xact_commit, pg_stat_get_db_xact_rollback(oid) AS xact_rollback, (pg_stat_get_db_blocks_fetched(oid) - pg_stat_get_db_blocks_hit(oid)) AS blks_read, diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out index 8e63340782..fb4dbad15d 100644 --- a/src/test/regress/expected/stats.out +++ b/src/test/regress/expected/stats.out @@ -782,6 +782,30 @@ SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC t (1 row) +-- Test that last_commit_lsn is incremented when a transaction commits +SELECT last_commit_lsn AS db_stat_last_commit_lsn FROM pg_stat_database WHERE datname = (SELECT current_database()) \gset +BEGIN; +CREATE TABLE test_commit_increments(i int); +COMMIT; +SELECT pg_stat_force_next_flush(); + pg_stat_force_next_flush +-------------------------- + +(1 row) + +SELECT last_commit_lsn > :'db_stat_last_commit_lsn'::pg_lsn FROM pg_stat_database WHERE datname = (SELECT current_database()); + ?column? +---------- + t +(1 row) + +SELECT :'db_stat_last_commit_lsn'::pg_lsn < pg_current_wal_insert_lsn(); + ?column? +---------- + t +(1 row) + +DROP TABLE test_commit_increments; -- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset -- Test pg_stat_wal (and make a temp table so our temp schema exists) diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql index fddf5a8277..7f6180826b 100644 --- a/src/test/regress/sql/stats.sql +++ b/src/test/regress/sql/stats.sql @@ -387,6 +387,16 @@ SELECT sessions AS db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC SELECT pg_stat_force_next_flush(); SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELECT current_database()); +-- Test that last_commit_lsn is incremented when a transaction commits +SELECT last_commit_lsn AS db_stat_last_commit_lsn FROM pg_stat_database WHERE datname = (SELECT current_database()) \gset +BEGIN; +CREATE TABLE test_commit_increments(i int); +COMMIT; +SELECT pg_stat_force_next_flush(); +SELECT last_commit_lsn > :'db_stat_last_commit_lsn'::pg_lsn FROM pg_stat_database WHERE datname = (SELECT current_database()); +SELECT :'db_stat_last_commit_lsn'::pg_lsn < pg_current_wal_insert_lsn(); +DROP TABLE test_commit_increments; + -- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset -- 2.39.3 (Apple Git-145)