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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
This commit is contained in:
Amit Kapila
2020-10-08 09:09:08 +05:30
parent 8d2a01ae12
commit 9868167500
16 changed files with 700 additions and 8 deletions

View File

@ -314,6 +314,15 @@ postgres 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 postgres: ser
</entry>
</row>
<row>
<entry><structname>pg_stat_replication_slots</structname><indexterm><primary>pg_stat_replication_slots</primary></indexterm></entry>
<entry>One row per replication slot, showing statistics about
replication slot usage.
See <link linkend="monitoring-pg-stat-replication-slots-view">
<structname>pg_stat_replication_slots</structname></link> for details.
</entry>
</row>
<row>
<entry><structname>pg_stat_wal_receiver</structname><indexterm><primary>pg_stat_wal_receiver</primary></indexterm></entry>
<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
</sect2>
<sect2 id="monitoring-pg-stat-replication-slots-view">
<title><structname>pg_stat_replication_slots</structname></title>
<indexterm>
<primary>pg_stat_replication_slots</primary>
</indexterm>
<para>
The <structname>pg_stat_replication_slots</structname> view will contain
one row per logical replication slot, showing statistics about its usage.
</para>
<table id="pg-stat-replication-slots-view" xreflabel="pg_stat_replication_slots">
<title><structname>pg_stat_replication_slots</structname> View</title>
<tgroup cols="1">
<thead>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
Column Type
</para>
<para>
Description
</para></entry>
</row>
</thead>
<tbody>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>name</structfield> <type>text</type>
</para>
<para>
A unique, cluster-wide identifier for the replication slot
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>spill_txns</structfield> <type>bigint</type>
</para>
<para>
Number of transactions spilled to disk after the memory used by
logical decoding exceeds <literal>logical_decoding_work_mem</literal>. The
counter gets incremented both for toplevel transactions and
subtransactions.
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>spill_count</structfield> <type>bigint</type>
</para>
<para>
Number of times transactions were spilled to disk. Transactions
may get spilled repeatedly, and this counter gets incremented on every
such invocation.
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>spill_bytes</structfield> <type>bigint</type>
</para>
<para>
Amount of decoded transaction data spilled to disk.
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>stats_reset</structfield> <type>timestamp with time zone</type>
</para>
<para>
Time at which these statistics were last reset
</para></entry>
</row>
</tbody>
</tgroup>
</table>
</sect2>
<sect2 id="monitoring-pg-stat-wal-receiver-view">
<title><structname>pg_stat_wal_receiver</structname></title>
@ -4802,6 +4893,27 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
can be granted EXECUTE to run the function.
</para></entry>
</row>
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
<primary>pg_stat_reset_replication_slot</primary>
</indexterm>
<function>pg_stat_reset_replication_slot</function> ( <type>text</type> )
<returnvalue>void</returnvalue>
</para>
<para>
Resets statistics to zero for a single replication slot, or for all
replication slots in the cluster. The argument can be either the name
of the slot to reset the stats or NULL. If the argument is NULL, all
counters shown in the <structname>pg_stat_replication_slots</structname>
view for all replication slots are reset.
</para>
<para>
This function is restricted to superusers by default, but other users
can be granted EXECUTE to run the function.
</para></entry>
</row>
</tbody>
</tgroup>
</table>