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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
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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)
{