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Adding the pg_stat_backend_transaction view
This view displays one row per server process, showing transaction statistics related to the current activity of that process. It currently displays the pid, the number of XIDs generated, the number of commits, the number of rollbacks and the time at which these statistics were last reset. It's built on top of a new function (pg_stat_get_backend_transactions()). The idea is the same as pg_stat_activity and pg_stat_get_activity(). Adding documentation and tests. XXX: Bump catversion
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‎doc/src/sgml/monitoring.sgml‎

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@@ -320,6 +320,20 @@ postgres 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 postgres: ser
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</entry>
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</row>
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<row>
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<entry>
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<structname>pg_stat_backend_transaction</structname>
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<indexterm><primary>pg_stat_backend_transaction</primary></indexterm>
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</entry>
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<entry>
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One row per server process, showing statistics related to
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the current activity of that process, such as number of commits and
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rollbacks.
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See <link linkend="monitoring-pg-stat-backend-transaction-view">
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<structname>pg_stat_backend_transaction</structname></link> for details.
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</entry>
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</row>
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<row>
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<entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
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<entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
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</note>
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</sect2>
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<sect2 id="monitoring-pg-stat-backend-transaction-view">
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<title><structname>pg_stat_backend_transaction</structname></title>
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<indexterm>
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<primary>pg_stat_backend_transaction</primary>
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</indexterm>
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<para>
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The <structname>pg_stat_backend_transaction</structname> view will have one row
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per server process, showing statistics related to
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the current activity of that process.
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</para>
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<table id="pg-stat-backend-transaction-view" xreflabel="pg_stat_backend_transaction">
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<title><structname>pg_stat_backend_transaction</structname> View</title>
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<tgroup cols="1">
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<thead>
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<row>
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<entry role="catalog_table_entry"><para role="column_definition">
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Column Type
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</para>
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<para>
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Description
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</para></entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry role="catalog_table_entry"><para role="column_definition">
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<structfield>pid</structfield> <type>integer</type>
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</para>
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<para>
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Process ID of this backend
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</para></entry>
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</row>
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<row>
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<entry role="catalog_table_entry"><para role="column_definition">
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<structfield>xid_count</structfield> <type>bigint</type>
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</para>
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<para>
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The number of XID that have been generated by the backend. It does not take
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into account virtual transaction ID on purpose.
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</para></entry>
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</row>
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<row>
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<entry role="catalog_table_entry"><para role="column_definition">
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<structfield>xact_commit</structfield> <type>bigint</type>
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</para>
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<para>
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The number of transactions that have been committed.
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</para></entry>
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</row>
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<row>
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<entry role="catalog_table_entry"><para role="column_definition">
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<structfield>xact_rollback</structfield> <type>bigint</type>
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</para>
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<para>
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The number of transactions that have been rolled back.
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</para></entry>
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</row>
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<row>
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<entry role="catalog_table_entry"><para role="column_definition">
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<structfield>stats_reset</structfield> <type>timestamp with time zone</type>
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</para>
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<para>
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Time at which these statistics were last reset
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</para></entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<note>
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<para>
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The view does not return statistics for the checkpointer,
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the background writer, the startup process and the autovacuum launcher.
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</para>
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</note>
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</sect2>
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<sect2 id="monitoring-pg-stat-replication-view">
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<title><structname>pg_stat_replication</structname></title>
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@@ -4990,6 +5089,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
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</para></entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<indexterm>
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<primary>pg_stat_get_backend_transactions</primary>
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</indexterm>
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<function>pg_stat_get_backend_transactions</function> ( <type>integer</type> )
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<returnvalue>setof record</returnvalue>
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</para>
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<para>
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Returns a record of transaction statistics about the backend with the
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specified process ID, or one record for each active backend in the system
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if <literal>NULL</literal> is specified. The fields returned are a
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subset of those in the <structname>pg_stat_backend_transaction</structname> view.
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</para></entry>
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</row>
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<row>
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<entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
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<indexterm>

‎src/backend/catalog/system_views.sql‎

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@@ -925,6 +925,15 @@ CREATE VIEW pg_stat_activity AS
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LEFT JOIN pg_database AS D ON (S.datid = D.oid)
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LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
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CREATE VIEW pg_stat_backend_transaction AS
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SELECT
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S.pid,
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S.xid_count,
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S.xact_commit,
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S.xact_rollback,
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S.stats_reset
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FROM pg_stat_get_backend_transactions(NULL) AS S;
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CREATE VIEW pg_stat_replication AS
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SELECT
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S.pid,

‎src/backend/utils/adt/pgstatfuncs.c‎

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@@ -706,6 +706,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
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return (Datum) 0;
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}
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/*
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* Returns statistics of PG backends.
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*/
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Datum
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pg_stat_get_backend_transactions(PG_FUNCTION_ARGS)
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{
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#define PG_STAT_GET_BACKEND_STATS_COLS 5
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int num_backends = pgstat_fetch_stat_numbackends();
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int curr_backend;
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int pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
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ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
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InitMaterializedSRF(fcinfo, 0);
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/* 1-based index */
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for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
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{
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/* for each row */
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Datum values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
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bool nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
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LocalPgBackendStatus *local_beentry;
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PgBackendStatus *beentry;
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PgStat_Backend *backend_stats;
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/* Get the next one in the list */
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local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
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beentry = &local_beentry->backendStatus;
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/* If looking for specific PID, ignore all the others */
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if (pid != -1 && beentry->st_procpid != pid)
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continue;
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backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
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values[0] = Int32GetDatum(beentry->st_procpid);
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if (!backend_stats)
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continue;
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values[1] = Int64GetDatum(backend_stats->xid_count);
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values[2] = Int64GetDatum(backend_stats->xact_commit);
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values[3] = Int64GetDatum(backend_stats->xact_rollback);
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if (backend_stats->stat_reset_timestamp != 0)
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values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
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else
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nulls[4] = true;
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tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
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/* If only a single backend was requested, and we found it, break. */
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if (pid != -1)
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break;
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}
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return (Datum) 0;
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}
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Datum
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pg_backend_pid(PG_FUNCTION_ARGS)

‎src/include/catalog/pg_proc.dat‎

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@@ -5657,6 +5657,15 @@
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proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
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proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
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prosrc => 'pg_stat_get_activity' },
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{ oid => '9555',
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descr => 'statistics: statistics about currently active backends',
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proname => 'pg_stat_get_backend_transactions', prorows => '100', proisstrict => 'f',
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proretset => 't', provolatile => 's', proparallel => 'r',
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prorettype => 'record', proargtypes => 'int4',
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proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
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proargmodes => '{i,o,o,o,o,o}',
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proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
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prosrc => 'pg_stat_get_backend_transactions' },
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{ oid => '6318', descr => 'describe wait events',
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proname => 'pg_get_wait_events', procost => '10', prorows => '250',
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proretset => 't', provolatile => 'v', prorettype => 'record',

‎src/test/regress/expected/rules.out‎

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@@ -1857,6 +1857,12 @@ pg_stat_archiver| SELECT archived_count,
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last_failed_time,
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stats_reset
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FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
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pg_stat_backend_transaction| SELECT pid,
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xid_count,
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xact_commit,
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xact_rollback,
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stats_reset
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FROM pg_stat_get_backend_transactions(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
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pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
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pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
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pg_stat_get_buf_alloc() AS buffers_alloc,

‎src/test/regress/expected/stats.out‎

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@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
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INSERT INTO trunc_stats_test1 DEFAULT VALUES;
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UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
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DELETE FROM trunc_stats_test1 WHERE id = 3;
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-- in passing, check that backend's commit is incrementing
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SELECT xact_commit AS xact_commit_before
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FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
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BEGIN;
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UPDATE trunc_stats_test1 SET id = id + 100;
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TRUNCATE trunc_stats_test1;
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INSERT INTO trunc_stats_test1 DEFAULT VALUES;
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COMMIT;
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SELECT pg_stat_force_next_flush();
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pg_stat_force_next_flush
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--------------------------
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(1 row)
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SELECT xact_commit AS xact_commit_after
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FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
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SELECT :xact_commit_after > :xact_commit_before;
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?column?
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----------
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t
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(1 row)
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-- use a savepoint: 1 insert, 1 live
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BEGIN;
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INSERT INTO trunc_stats_test2 DEFAULT VALUES;

‎src/test/regress/sql/stats.sql‎

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@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
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UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
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DELETE FROM trunc_stats_test1 WHERE id = 3;
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-- in passing, check that backend's commit is incrementing
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SELECT xact_commit AS xact_commit_before
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FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
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BEGIN;
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UPDATE trunc_stats_test1 SET id = id + 100;
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TRUNCATE trunc_stats_test1;
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INSERT INTO trunc_stats_test1 DEFAULT VALUES;
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COMMIT;
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SELECT pg_stat_force_next_flush();
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SELECT xact_commit AS xact_commit_after
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FROM pg_stat_backend_transaction WHERE pid = pg_backend_pid() \gset
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SELECT :xact_commit_after > :xact_commit_before;
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-- use a savepoint: 1 insert, 1 live
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BEGIN;
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INSERT INTO trunc_stats_test2 DEFAULT VALUES;

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