Re: Contradicting information on the "vacuum threshold"
| От | Erwin Brandstetter |
|---|---|
| Тема | Re: Contradicting information on the "vacuum threshold" |
| Дата | |
| Msg-id | CAGHENJ4S6fZnqDEnhUrkmmfjEBeA+WD+oOwZtMHs11GNoy8ftA@mail.gmail.com обсуждение исходный текст |
| Ответ на | [DOCS] Contradicting information on the "vacuum threshold" (Erwin Brandstetter <brsaweda@gmail.com>) |
| Список | pgsql-docs |
On 11 August 2017 at 23:54, Erwin Brandstetter <brsaweda@gmail.com> wrote:
On the one hand the manual for autovacuum_analyze_threshold claims here:I suggest to either clarify the manual or change the code to actually use >= instead of > ... and update the explanation for autovacuum accordingly.
https://www.postgresql.org/docs/current/static/runtime- config-autovacuum.html#GUC- AUTOVACUUM-ANALYZE-THRESHOLD
> Specifies the minimum number of inserted, updated or deleted tuples needed to trigger an ANALYZE in any one table.
Similar in pg_settings.short_desc:
> Minimum number of tuple inserts, updates, or deletes prior to analyze.
"Minimum" indicates "row_count >= vacuum threshold". (Well "prior" makes that less clear ..)
On the other hand the manual explains here:
https://www.postgresql.org/docs/current/static/routine- vacuuming.html#AUTOVACUUM
> Otherwise, if the number of tuples obsoleted since the last VACUUM exceeds the "vacuum threshold", the table is vacuumed.
"Exceeds" indicates "row_count > vacuum threshold".
Actual test results seem to support "row_count > vacuum threshold". See test case here:
https://dba.stackexchange.com/questions/181960/tiny-table- causes-extreme-performance- degradation-fixed-by-forced- vacuum-why/183283#183283
Same for autovacuum_vacuum_threshold.
Still incorrect in the manual. The specified number of obsoleted rows does *not* yet trigger an
ANALYZE. Only the next one does. Off-by-one error.minimum number of inserted, updated or deleted tuples
with:
number of inserted, updated or deleted tuples that must be exceeded
Regards
Erwin
В списке pgsql-docs по дате отправления: