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Amit Kapila
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Track statistics for spilling of changes from ReorderBuffer.
This adds the statistics about transactions spilled to disk from ReorderBuffer. Users can query the pg_stat_replication_slots view to check these stats and call pg_stat_reset_replication_slot to reset the stats of a particular slot. Users can pass NULL in pg_stat_reset_replication_slot to reset stats of all the slots. This commit extends the statistics collector to track this information about slots. Author: Sawada Masahiko and Amit Kapila Reviewed-by: Amit Kapila and Dilip Kumar Discussion: https://postgr.es/m/CA+fd4k5_pPAYRTDrO2PbtTOe0eHQpBvuqmCr8ic39uTNmR49Eg@mail.gmail.com
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‎doc/src/sgml/monitoring.sgml‎

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@@ -314,6 +314,15 @@ 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><structname>pg_stat_replication_slots</structname><indexterm><primary>pg_stat_replication_slots</primary></indexterm></entry>
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<entry>One row per replication slot, showing statistics about
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replication slot usage.
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See <link linkend="monitoring-pg-stat-replication-slots-view">
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<structname>pg_stat_replication_slots</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_wal_receiver</structname><indexterm><primary>pg_stat_wal_receiver</primary></indexterm></entry>
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<entry>Only one row, showing statistics about the WAL receiver from
@@ -2552,6 +2561,88 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
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</sect2>
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<sect2 id="monitoring-pg-stat-replication-slots-view">
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<title><structname>pg_stat_replication_slots</structname></title>
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<indexterm>
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<primary>pg_stat_replication_slots</primary>
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</indexterm>
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<para>
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The <structname>pg_stat_replication_slots</structname> view will contain
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one row per logical replication slot, showing statistics about its usage.
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</para>
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<table id="pg-stat-replication-slots-view" xreflabel="pg_stat_replication_slots">
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<title><structname>pg_stat_replication_slots</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>name</structfield> <type>text</type>
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</para>
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<para>
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A unique, cluster-wide identifier for the replication slot
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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>spill_txns</structfield> <type>bigint</type>
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</para>
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<para>
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Number of transactions spilled to disk after the memory used by
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logical decoding exceeds <literal>logical_decoding_work_mem</literal>. The
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counter gets incremented both for toplevel transactions and
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subtransactions.
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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>spill_count</structfield> <type>bigint</type>
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</para>
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<para>
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Number of times transactions were spilled to disk. Transactions
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may get spilled repeatedly, and this counter gets incremented on every
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such invocation.
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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>spill_bytes</structfield> <type>bigint</type>
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</para>
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<para>
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Amount of decoded transaction data spilled to disk.
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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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</sect2>
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<sect2 id="monitoring-pg-stat-wal-receiver-view">
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<title><structname>pg_stat_wal_receiver</structname></title>
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can be granted EXECUTE to run the function.
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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_reset_replication_slot</primary>
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</indexterm>
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<function>pg_stat_reset_replication_slot</function> ( <type>text</type> )
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<returnvalue>void</returnvalue>
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</para>
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<para>
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Resets statistics to zero for a single replication slot, or for all
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replication slots in the cluster. The argument can be either the name
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of the slot to reset the stats or NULL. If the argument is NULL, all
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counters shown in the <structname>pg_stat_replication_slots</structname>
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view for all replication slots are reset.
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</para>
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<para>
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This function is restricted to superusers by default, but other users
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can be granted EXECUTE to run the function.
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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>

‎src/backend/catalog/system_views.sql‎

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@@ -796,6 +796,15 @@ CREATE VIEW pg_stat_replication AS
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JOIN pg_stat_get_wal_senders() AS W ON (S.pid = W.pid)
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LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
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CREATE VIEW pg_stat_replication_slots AS
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SELECT
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s.name,
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s.spill_txns,
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s.spill_count,
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s.spill_bytes,
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s.stats_reset
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FROM pg_stat_get_replication_slots() AS s;
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CREATE VIEW pg_stat_slru AS
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SELECT
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s.name,
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REVOKE EXECUTE ON FUNCTION pg_stat_reset_slru(text) FROM public;
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REVOKE EXECUTE ON FUNCTION pg_stat_reset_single_table_counters(oid) FROM public;
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REVOKE EXECUTE ON FUNCTION pg_stat_reset_single_function_counters(oid) FROM public;
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REVOKE EXECUTE ON FUNCTION pg_stat_reset_replication_slot(text) FROM public;
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REVOKE EXECUTE ON FUNCTION lo_import(text) FROM public;
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REVOKE EXECUTE ON FUNCTION lo_import(text, oid) FROM public;

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