Implement rate-limiting logic on how often backends will attempt to send
messages to the stats collector. This avoids the problem that enabling stats_row_level for autovacuum has a significant overhead for short read-only transactions, as noted by Arjen van der Meijden. We can avoid an extra gettimeofday call by piggybacking on the one done for WAL-logging xact commit or abort (although that doesn't help read-only transactions, since they don't WAL-log anything). In my proposal for this, I noted that we could change the WAL log entries for commit/abort to record full TimestampTz precision, instead of only time_t as at present. That's not done in this patch, but will be committed separately.
This commit is contained in:
Tom Lane
parent
57b82bf324
commit
957d08c81f
@ -10,7 +10,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.240 2007/04/26 23:24:44 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.241 2007/04/30 03:23:48 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -160,11 +160,13 @@ static CommandId currentCommandId;
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/*
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* xactStartTimestamp is the value of transaction_timestamp().
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* stmtStartTimestamp is the value of statement_timestamp().
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* xactStopTimestamp is the time at which we log a commit or abort WAL record.
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* These do not change as we enter and exit subtransactions, so we don't
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* keep them inside the TransactionState stack.
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*/
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static TimestampTz xactStartTimestamp;
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static TimestampTz stmtStartTimestamp;
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static TimestampTz xactStopTimestamp;
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/*
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* GID to be used for preparing the current transaction. This is also
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@ -435,6 +437,20 @@ GetCurrentStatementStartTimestamp(void)
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return stmtStartTimestamp;
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}
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/*
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* GetCurrentTransactionStopTimestamp
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*
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* We return current time if the transaction stop time hasn't been set
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* (which can happen if we decide we don't need to log an XLOG record).
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*/
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TimestampTz
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GetCurrentTransactionStopTimestamp(void)
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{
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if (xactStopTimestamp != 0)
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return xactStopTimestamp;
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return GetCurrentTimestamp();
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}
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/*
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* SetCurrentStatementStartTimestamp
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*/
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@ -444,6 +460,15 @@ SetCurrentStatementStartTimestamp(void)
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stmtStartTimestamp = GetCurrentTimestamp();
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}
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/*
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* SetCurrentTransactionStopTimestamp
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*/
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static inline void
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SetCurrentTransactionStopTimestamp(void)
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{
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xactStopTimestamp = GetCurrentTimestamp();
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}
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/*
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* GetCurrentTransactionNestLevel
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*
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@ -747,7 +772,8 @@ RecordTransactionCommit(void)
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*/
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MyProc->inCommit = true;
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xlrec.xtime = time(NULL);
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SetCurrentTransactionStopTimestamp();
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xlrec.xtime = timestamptz_to_time_t(xactStopTimestamp);
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xlrec.nrels = nrels;
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xlrec.nsubxacts = nchildren;
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rdata[0].data = (char *) (&xlrec);
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@ -1042,7 +1068,8 @@ RecordTransactionAbort(void)
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xl_xact_abort xlrec;
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XLogRecPtr recptr;
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xlrec.xtime = time(NULL);
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SetCurrentTransactionStopTimestamp();
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xlrec.xtime = timestamptz_to_time_t(xactStopTimestamp);
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xlrec.nrels = nrels;
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xlrec.nsubxacts = nchildren;
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rdata[0].data = (char *) (&xlrec);
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@ -1415,9 +1442,11 @@ StartTransaction(void)
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/*
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* set transaction_timestamp() (a/k/a now()). We want this to be the same
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* as the first command's statement_timestamp(), so don't do a fresh
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* GetCurrentTimestamp() call (which'd be expensive anyway).
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* GetCurrentTimestamp() call (which'd be expensive anyway). Also,
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* mark xactStopTimestamp as unset.
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*/
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xactStartTimestamp = stmtStartTimestamp;
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xactStopTimestamp = 0;
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pgstat_report_txn_timestamp(xactStartTimestamp);
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/*
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/commands/analyze.c,v 1.106 2007/04/19 16:26:44 alvherre Exp $
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* $PostgreSQL: pgsql/src/backend/commands/analyze.c,v 1.107 2007/04/30 03:23:48 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -468,29 +468,15 @@ analyze_rel(Oid relid, VacuumStmt *vacstmt)
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/* Log the action if appropriate */
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if (IsAutoVacuumWorkerProcess() && Log_autovacuum >= 0)
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{
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long diff = 0L;
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if (Log_autovacuum > 0)
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{
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TimestampTz endtime;
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int usecs;
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long secs;
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endtime = GetCurrentTimestamp();
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TimestampDifference(starttime, endtime, &secs, &usecs);
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diff = secs * 1000 + usecs / 1000;
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}
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if (Log_autovacuum == 0 || diff >= Log_autovacuum)
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{
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if (Log_autovacuum == 0 ||
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TimestampDifferenceExceeds(starttime, GetCurrentTimestamp(),
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Log_autovacuum))
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ereport(LOG,
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(errmsg("automatic analyze of table \"%s.%s.%s\" system usage: %s",
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get_database_name(MyDatabaseId),
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get_namespace_name(RelationGetNamespace(onerel)),
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RelationGetRelationName(onerel),
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pg_rusage_show(&ru0))));
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}
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}
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}
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@ -36,7 +36,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.87 2007/04/19 16:26:44 alvherre Exp $
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* $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.88 2007/04/30 03:23:48 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -217,22 +217,9 @@ lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt)
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/* and log the action if appropriate */
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if (IsAutoVacuumWorkerProcess() && Log_autovacuum >= 0)
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{
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long diff = 0L;
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if (Log_autovacuum > 0)
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{
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TimestampTz endtime;
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int usecs;
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long secs;
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endtime = GetCurrentTimestamp();
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TimestampDifference(starttime, endtime, &secs, &usecs);
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diff = secs * 1000 + usecs / 1000;
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}
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if (Log_autovacuum == 0 || diff >= Log_autovacuum)
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{
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if (Log_autovacuum == 0 ||
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TimestampDifferenceExceeds(starttime, GetCurrentTimestamp(),
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Log_autovacuum))
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ereport(LOG,
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(errmsg("automatic vacuum of table \"%s.%s.%s\": index scans: %d\n"
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"pages: %d removed, %d remain\n"
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@ -245,7 +232,6 @@ lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt)
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vacrelstats->pages_removed, vacrelstats->rel_pages,
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vacrelstats->tuples_deleted, vacrelstats->rel_tuples,
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pg_rusage_show(&ru0))));
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}
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}
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}
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@ -13,7 +13,7 @@
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*
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* Copyright (c) 2001-2007, PostgreSQL Global Development Group
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*
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* $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.153 2007/04/21 04:10:53 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.154 2007/04/30 03:23:49 tgl Exp $
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* ----------
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*/
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#include "postgres.h"
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@ -608,15 +608,34 @@ void allow_immediate_pgstat_restart(void)
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/* ----------
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* pgstat_report_tabstat() -
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*
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* Called from tcop/postgres.c to send the so far collected
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* per table access statistics to the collector.
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* Called from tcop/postgres.c to send the so far collected per-table
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* access statistics to the collector. Note that this is called only
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* when not within a transaction, so it is fair to use transaction stop
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* time as an approximation of current time.
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* ----------
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*/
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void
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pgstat_report_tabstat(void)
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{
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static TimestampTz last_report = 0;
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TimestampTz now;
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/* Don't expend a clock check if nothing to do */
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if (RegularTabStat.tsa_used == 0 &&
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SharedTabStat.tsa_used == 0)
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return;
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/*
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* For each message buffer used during the last query set the header
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* Don't send a message unless it's been at least PGSTAT_STAT_INTERVAL
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* msec since we last sent one.
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*/
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now = GetCurrentTransactionStopTimestamp();
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if (!TimestampDifferenceExceeds(last_report, now, PGSTAT_STAT_INTERVAL))
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return;
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last_report = now;
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/*
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* For each message buffer used during the last queries, set the header
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* fields and send it out; then mark the entries unused.
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*/
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pgstat_report_one_tabstat(&RegularTabStat, MyDatabaseId);
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/utils/adt/timestamp.c,v 1.174 2007/02/27 23:48:09 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/utils/adt/timestamp.c,v 1.175 2007/04/30 03:23:49 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -1238,6 +1238,27 @@ TimestampDifference(TimestampTz start_time, TimestampTz stop_time,
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}
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}
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/*
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* TimestampDifferenceExceeds -- report whether the difference between two
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* timestamps is >= a threshold (expressed in milliseconds)
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*
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* Both inputs must be ordinary finite timestamps (in current usage,
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* they'll be results from GetCurrentTimestamp()).
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*/
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bool
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TimestampDifferenceExceeds(TimestampTz start_time,
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TimestampTz stop_time,
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int msec)
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{
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TimestampTz diff = stop_time - start_time;
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#ifdef HAVE_INT64_TIMESTAMP
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return (diff >= msec * INT64CONST(1000));
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#else
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return (diff * 1000.0 >= msec);
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#endif
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}
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/*
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* Convert a time_t to TimestampTz.
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*
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/access/xact.h,v 1.85 2007/03/13 00:33:42 tgl Exp $
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* $PostgreSQL: pgsql/src/include/access/xact.h,v 1.86 2007/04/30 03:23:49 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -142,6 +142,7 @@ extern SubTransactionId GetCurrentSubTransactionId(void);
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extern CommandId GetCurrentCommandId(void);
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extern TimestampTz GetCurrentTransactionStartTimestamp(void);
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extern TimestampTz GetCurrentStatementStartTimestamp(void);
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extern TimestampTz GetCurrentTransactionStopTimestamp(void);
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extern void SetCurrentStatementStartTimestamp(void);
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extern int GetCurrentTransactionNestLevel(void);
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extern bool TransactionIdIsCurrentTransactionId(TransactionId xid);
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@ -6,7 +6,7 @@
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* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/utils/timestamp.h,v 1.67 2007/02/16 03:39:45 momjian Exp $
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* $PostgreSQL: pgsql/src/include/utils/timestamp.h,v 1.68 2007/04/30 03:23:49 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -311,6 +311,9 @@ extern TimestampTz GetCurrentTimestamp(void);
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extern void TimestampDifference(TimestampTz start_time, TimestampTz stop_time,
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long *secs, int *microsecs);
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extern bool TimestampDifferenceExceeds(TimestampTz start_time,
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TimestampTz stop_time,
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int msec);
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extern TimestampTz time_t_to_timestamptz(time_t tm);
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extern time_t timestamptz_to_time_t(TimestampTz t);
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@ -73,6 +73,14 @@ SELECT count(*) FROM tenk2 WHERE unique1 = 1;
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1
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(1 row)
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-- force the rate-limiting logic in pgstat_report_tabstat() to time out
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-- and send a message
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SELECT pg_sleep(1.0);
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pg_sleep
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----------
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(1 row)
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-- wait for stats collector to update
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SELECT wait_for_stats();
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wait_for_stats
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@ -60,6 +60,10 @@ SELECT count(*) FROM tenk2;
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-- do an indexscan
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SELECT count(*) FROM tenk2 WHERE unique1 = 1;
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-- force the rate-limiting logic in pgstat_report_tabstat() to time out
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-- and send a message
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SELECT pg_sleep(1.0);
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-- wait for stats collector to update
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SELECT wait_for_stats();
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