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Count updates that move row to a new page.

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Add pgstat counter to track row updates that result in the successor
version going to a new heap page, leaving behind an original version
whose t_ctid points to the new version.  The current count is shown by
the n_tup_newpage_upd column of each of the pg_stat_*_tables views.

The new n_tup_newpage_upd column complements the existing n_tup_hot_upd
and n_tup_upd columns.  Tables that have high n_tup_newpage_upd values
(relative to n_tup_upd) are good candidates for tuning heap fillfactor.

Corey Huinker, with small tweaks by me.

Author: Corey Huinker <corey.huinker@gmail.com>
Reviewed-By: Peter Geoghegan <pg@bowt.ie>
Reviewed-By: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CADkLM=ded21M9iZ36hHm-vj2rE2d=zcKpUQMds__Xm2pxLfHKA@mail.gmail.com
This commit is contained in:
Peter Geoghegan 2023-03-23 11:16:17 -07:00
parent 3b50275b12
commit ae4fdde135
9 changed files with 80 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
doc/src/sgml/monitoring.sgml
View File

@ -4789,7 +4789,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
<structfield>n_tup_ins</structfield> <type>bigint</type>
</para>
<para>
Number of rows inserted
Total number of rows inserted
</para></entry>
</row>
@ -4798,7 +4798,10 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
<structfield>n_tup_upd</structfield> <type>bigint</type>
</para>
<para>
Number of rows updated (includes <link linkend="storage-hot">HOT updated rows</link>)
Total number of rows updated. (This includes row updates
counted in <structfield>n_tup_hot_upd</structfield> and
<structfield>n_tup_newpage_upd</structfield>, and remaining
non-<acronym>HOT</acronym> updates.)
</para></entry>
</row>
@ -4807,7 +4810,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
<structfield>n_tup_del</structfield> <type>bigint</type>
</para>
<para>
Number of rows deleted
Total number of rows deleted
</para></entry>
</row>
@ -4816,8 +4819,23 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
<structfield>n_tup_hot_upd</structfield> <type>bigint</type>
</para>
<para>
Number of rows HOT updated (i.e., with no separate index
update required)
Number of rows <link linkend="storage-hot">HOT updated</link>.
These are updates where no successor versions are required in
indexes.
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>n_tup_newpage_upd</structfield> <type>bigint</type>
</para>
<para>
Number of rows updated where the successor version goes onto a
<emphasis>new</emphasis> heap page, leaving behind an original
version with a
<link linkend="storage-tuple-layout"><structfield>t_ctid</structfield>
field</link> that points to a different heap page. These are
always non-<acronym>HOT</acronym> updates.
</para></entry>
</row>

2
src/backend/access/heap/heapam.c
View File

@ -3803,7 +3803,7 @@ l2:
if (have_tuple_lock)
UnlockTupleTuplock(relation, &(oldtup.t_self), *lockmode);
pgstat_count_heap_update(relation, use_hot_update);
pgstat_count_heap_update(relation, use_hot_update, newbuf != buffer);
/*
* If heaptup is a private copy, release it. Don't forget to copy t_self

4
src/backend/catalog/system_views.sql
View File

@ -665,6 +665,7 @@ CREATE VIEW pg_stat_all_tables AS
pg_stat_get_tuples_updated(C.oid) AS n_tup_upd,
pg_stat_get_tuples_deleted(C.oid) AS n_tup_del,
pg_stat_get_tuples_hot_updated(C.oid) AS n_tup_hot_upd,
pg_stat_get_tuples_newpage_updated(C.oid) AS n_tup_newpage_upd,
pg_stat_get_live_tuples(C.oid) AS n_live_tup,
pg_stat_get_dead_tuples(C.oid) AS n_dead_tup,
pg_stat_get_mod_since_analyze(C.oid) AS n_mod_since_analyze,
@ -696,7 +697,8 @@ CREATE VIEW pg_stat_xact_all_tables AS
pg_stat_get_xact_tuples_inserted(C.oid) AS n_tup_ins,
pg_stat_get_xact_tuples_updated(C.oid) AS n_tup_upd,
pg_stat_get_xact_tuples_deleted(C.oid) AS n_tup_del,
pg_stat_get_xact_tuples_hot_updated(C.oid) AS n_tup_hot_upd
pg_stat_get_xact_tuples_hot_updated(C.oid) AS n_tup_hot_upd,
pg_stat_get_xact_tuples_newpage_updated(C.oid) AS n_tup_newpage_upd
FROM pg_class C LEFT JOIN
pg_index I ON C.oid = I.indrelid
LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)

12
src/backend/utils/activity/pgstat_relation.c
View File

@ -373,8 +373,10 @@ pgstat_count_heap_insert(Relation rel, PgStat_Counter n)
* count a tuple update
*/
void
pgstat_count_heap_update(Relation rel, bool hot)
pgstat_count_heap_update(Relation rel, bool hot, bool newpage)
{
Assert(!(hot && newpage));
if (pgstat_should_count_relation(rel))
{
PgStat_TableStatus *pgstat_info = rel->pgstat_info;
@ -382,9 +384,14 @@ pgstat_count_heap_update(Relation rel, bool hot)
ensure_tabstat_xact_level(pgstat_info);
pgstat_info->trans->tuples_updated++;
/* t_tuples_hot_updated is nontransactional, so just advance it */
/*
* t_tuples_hot_updated and t_tuples_newpage_updated counters are
* nontransactional, so just advance them
*/
if (hot)
pgstat_info->t_counts.t_tuples_hot_updated++;
else if (newpage)
pgstat_info->t_counts.t_tuples_newpage_updated++;
}
}
@ -804,6 +811,7 @@ pgstat_relation_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
tabentry->tuples_updated += lstats->t_counts.t_tuples_updated;
tabentry->tuples_deleted += lstats->t_counts.t_tuples_deleted;
tabentry->tuples_hot_updated += lstats->t_counts.t_tuples_hot_updated;
tabentry->tuples_newpage_updated += lstats->t_counts.t_tuples_newpage_updated;
/*
* If table was truncated/dropped, first reset the live/dead counters.

18
src/backend/utils/adt/pgstatfuncs.c
View File

@ -92,6 +92,9 @@ PG_STAT_GET_RELENTRY_INT64(tuples_fetched)
/* pg_stat_get_tuples_hot_updated */
PG_STAT_GET_RELENTRY_INT64(tuples_hot_updated)
/* pg_stat_get_tuples_newpage_updated */
PG_STAT_GET_RELENTRY_INT64(tuples_newpage_updated)
/* pg_stat_get_tuples_inserted */
PG_STAT_GET_RELENTRY_INT64(tuples_inserted)
@ -1618,6 +1621,21 @@ pg_stat_get_xact_tuples_hot_updated(PG_FUNCTION_ARGS)
PG_RETURN_INT64(result);
}
Datum
pg_stat_get_xact_tuples_newpage_updated(PG_FUNCTION_ARGS)
{
Oid relid = PG_GETARG_OID(0);
int64 result;
PgStat_TableStatus *tabentry;
if ((tabentry = find_tabstat_entry(relid)) == NULL)
result = 0;
else
result = (int64) (tabentry->t_counts.t_tuples_newpage_updated);
PG_RETURN_INT64(result);
}
Datum
pg_stat_get_xact_blocks_fetched(PG_FUNCTION_ARGS)
{

2
src/include/catalog/catversion.h
View File

@ -57,6 +57,6 @@
*/
/* yyyymmddN */
#define CATALOG_VERSION_NO 202303181
#define CATALOG_VERSION_NO 202303231
#endif

10
src/include/catalog/pg_proc.dat
View File

@ -5360,6 +5360,11 @@
proname => 'pg_stat_get_tuples_hot_updated', provolatile => 's',
proparallel => 'r', prorettype => 'int8', proargtypes => 'oid',
prosrc => 'pg_stat_get_tuples_hot_updated' },
{ oid => '8614',
descr => 'statistics: number of tuples updated onto a new page',
proname => 'pg_stat_get_tuples_newpage_updated', provolatile => 's',
proparallel => 'r', prorettype => 'int8', proargtypes => 'oid',
prosrc => 'pg_stat_get_tuples_newpage_updated' },
{ oid => '2878', descr => 'statistics: number of live tuples',
proname => 'pg_stat_get_live_tuples', provolatile => 's', proparallel => 'r',
prorettype => 'int8', proargtypes => 'oid',
@ -5823,6 +5828,11 @@
proname => 'pg_stat_get_xact_tuples_hot_updated', provolatile => 'v',
proparallel => 'r', prorettype => 'int8', proargtypes => 'oid',
prosrc => 'pg_stat_get_xact_tuples_hot_updated' },
{ oid => '8615',
descr => 'statistics: number of tuples updated onto a new page in current transaction',
proname => 'pg_stat_get_xact_tuples_newpage_updated', provolatile => 'v',
proparallel => 'r', prorettype => 'int8', proargtypes => 'oid',
prosrc => 'pg_stat_get_xact_tuples_newpage_updated' },
{ oid => '3044',
descr => 'statistics: number of blocks fetched in current transaction',
proname => 'pg_stat_get_xact_blocks_fetched', provolatile => 'v',

8
src/include/pgstat.h
View File

@ -151,8 +151,8 @@ typedef struct PgStat_BackendSubEntry
* the index AM, while tuples_fetched is the number of tuples successfully
* fetched by heap_fetch under the control of simple indexscans for this index.
*
* tuples_inserted/updated/deleted/hot_updated count attempted actions,
* regardless of whether the transaction committed. delta_live_tuples,
* tuples_inserted/updated/deleted/hot_updated/newpage_updated count attempted
* actions, regardless of whether the transaction committed. delta_live_tuples,
* delta_dead_tuples, and changed_tuples are set depending on commit or abort.
* Note that delta_live_tuples and delta_dead_tuples can be negative!
* ----------
@ -168,6 +168,7 @@ typedef struct PgStat_TableCounts
PgStat_Counter t_tuples_updated;
PgStat_Counter t_tuples_deleted;
PgStat_Counter t_tuples_hot_updated;
PgStat_Counter t_tuples_newpage_updated;
bool t_truncdropped;
PgStat_Counter t_delta_live_tuples;
@ -401,6 +402,7 @@ typedef struct PgStat_StatTabEntry
PgStat_Counter tuples_updated;
PgStat_Counter tuples_deleted;
PgStat_Counter tuples_hot_updated;
PgStat_Counter tuples_newpage_updated;
PgStat_Counter live_tuples;
PgStat_Counter dead_tuples;
@ -616,7 +618,7 @@ extern void pgstat_report_analyze(Relation rel,
} while (0)
extern void pgstat_count_heap_insert(Relation rel, PgStat_Counter n);
extern void pgstat_count_heap_update(Relation rel, bool hot);
extern void pgstat_count_heap_update(Relation rel, bool hot, bool newpage);
extern void pgstat_count_heap_delete(Relation rel);
extern void pgstat_count_truncate(Relation rel);
extern void pgstat_update_heap_dead_tuples(Relation rel, int delta);

12
src/test/regress/expected/rules.out
View File

@ -1789,6 +1789,7 @@ pg_stat_all_tables| SELECT c.oid AS relid,
pg_stat_get_tuples_updated(c.oid) AS n_tup_upd,
pg_stat_get_tuples_deleted(c.oid) AS n_tup_del,
pg_stat_get_tuples_hot_updated(c.oid) AS n_tup_hot_upd,
pg_stat_get_tuples_newpage_updated(c.oid) AS n_tup_newpage_upd,
pg_stat_get_live_tuples(c.oid) AS n_live_tup,
pg_stat_get_dead_tuples(c.oid) AS n_dead_tup,
pg_stat_get_mod_since_analyze(c.oid) AS n_mod_since_analyze,
@ -2146,6 +2147,7 @@ pg_stat_sys_tables| SELECT relid,
n_tup_upd,
n_tup_del,
n_tup_hot_upd,
n_tup_newpage_upd,
n_live_tup,
n_dead_tup,
n_mod_since_analyze,
@ -2193,6 +2195,7 @@ pg_stat_user_tables| SELECT relid,
n_tup_upd,
n_tup_del,
n_tup_hot_upd,
n_tup_newpage_upd,
n_live_tup,
n_dead_tup,
n_mod_since_analyze,
@ -2244,7 +2247,8 @@ pg_stat_xact_all_tables| SELECT c.oid AS relid,
pg_stat_get_xact_tuples_inserted(c.oid) AS n_tup_ins,
pg_stat_get_xact_tuples_updated(c.oid) AS n_tup_upd,
pg_stat_get_xact_tuples_deleted(c.oid) AS n_tup_del,
pg_stat_get_xact_tuples_hot_updated(c.oid) AS n_tup_hot_upd
pg_stat_get_xact_tuples_hot_updated(c.oid) AS n_tup_hot_upd,
pg_stat_get_xact_tuples_newpage_updated(c.oid) AS n_tup_newpage_upd
FROM ((pg_class c
LEFT JOIN pg_index i ON ((c.oid = i.indrelid)))
LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace)))
@ -2260,7 +2264,8 @@ pg_stat_xact_sys_tables| SELECT relid,
n_tup_ins,
n_tup_upd,
n_tup_del,
n_tup_hot_upd
n_tup_hot_upd,
n_tup_newpage_upd
FROM pg_stat_xact_all_tables
WHERE ((schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (schemaname ~ '^pg_toast'::text));
pg_stat_xact_user_functions| SELECT p.oid AS funcid,
@ -2282,7 +2287,8 @@ pg_stat_xact_user_tables| SELECT relid,
n_tup_ins,
n_tup_upd,
n_tup_del,
n_tup_hot_upd
n_tup_hot_upd,
n_tup_newpage_upd
FROM pg_stat_xact_all_tables
WHERE ((schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (schemaname !~ '^pg_toast'::text));
pg_statio_all_indexes| SELECT c.oid AS relid,