database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-06-13 07:41:39 +03:00
Code Activity

pgstat: scaffolding for transactional stats creation / drop.

Browse Source 
One problematic part of the current statistics collector design is that there
is no reliable way of getting rid of statistics entries. Because of that
pgstat_vacuum_stat() (called by [auto-]vacuum) matches all stats for the
current database with the catalog contents and tries to drop now-superfluous
entries. That's quite expensive. What's worse, it doesn't work on physical
replicas, despite physical replicas collection statistics entries.

This commit introduces infrastructure to create / drop statistics entries
transactionally, together with the underlying catalog objects (functions,
relations, subscriptions). pgstat_xact.c maintains a list of stats entries
created / dropped transactionally in the current transaction. To ensure the
removal of statistics entries is durable dropped statistics entries are
included in commit / abort (and prepare) records, which also ensures that
stats entries are dropped on standbys.

Statistics entries created separately from creating the underlying catalog
object (e.g. when stats were previously lost due to an immediate restart)
are *not* WAL logged. However that can only happen outside of the transaction
creating the catalog object, so it does not lead to "leaked" statistics
entries.

For this to work, functions creating / dropping functions / relations /
subscriptions need to call into pgstat. For subscriptions this was already
done when dropping subscriptions, via pgstat_report_subscription_drop() (now
renamed to pgstat_drop_subscription()).

This commit does not actually drop stats yet, it just provides the
infrastructure. It is however a largely independent piece of infrastructure,
so committing it separately makes sense.

Bumps XLOG_PAGE_MAGIC.

Author: Andres Freund <andres@anarazel.de>
Reviewed-By: Thomas Munro <thomas.munro@gmail.com>
Reviewed-By: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Discussion: https://postgr.es/m/20220303021600.hs34ghqcw6zcokdh@alap3.anarazel.de
This commit is contained in:
Andres Freund
2022-04-06 18:22:22 -07:00
parent 8fb580a35c
commit 8b1dccd37c
18 changed files with 526 additions and 38 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
src/backend/commands/subscriptioncmds.c
View File

@ -738,6 +738,8 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
table_close(rel, RowExclusiveLock);
pgstat_create_subscription(subid);
if (opts.enabled)
ApplyLauncherWakeupAtCommit();
@ -1592,7 +1594,7 @@ DropSubscription(DropSubscriptionStmt *stmt, bool isTopLevel)
* gets lost.
*/
if (slotname)
pgstat_report_subscription_drop(subid);
pgstat_drop_subscription(subid);
table_close(rel, NoLock);
}