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[DOCS] Contradicting information on the "vacuum threshold" - Mailing list pgsql-docs

From Erwin Brandstetter
Subject [DOCS] Contradicting information on the "vacuum threshold"
Date
Msg-id CAGHENJ53HMDAWn64g9hDW5Rg-UtFvExu4VoDhjYKS-CSCmOSTw@mail.gmail.com
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Responses Re: Contradicting information on the "vacuum threshold"
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On the one hand the manual for autovacuum_analyze_threshold claims here:

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

I suggest to either clarify the manual or change the code to actually use >= instead of > ... and update the explanation for autovacuum accordingly.

Same for autovacuum_vacuum_threshold.

Regards
Erwin Brandstetter

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