Re: Surprising dead_tuple_count from pgstattuple - Mailing list pgsql-hackers

From Itagaki Takahiro
Subject Re: Surprising dead_tuple_count from pgstattuple
Date
Msg-id AANLkTim0F1XV6LY6z8hFhDU4N5-6FcHh8nikEpkCF9vr@mail.gmail.com
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In response to Surprising dead_tuple_count from pgstattuple  (Gordon Shannon <gordo169@gmail.com>)
Responses Re: Surprising dead_tuple_count from pgstattuple
List pgsql-hackers
2010/8/7 Gordon Shannon <gordo169@gmail.com>:
> 1. I delete 10,000 rows.
> pgstattuple.dead_tuple_count -> 10000
>
> 2. I delete 15,000 more rows.
> pgstattuple.dead_tuple_count -> 15000 ??
>
> pgstattuple now appears to count the earlier 10K deleted tuples as no longer
> dead, but free space.

I think it's expected behavior that comes from HOT page reclaim.
The second DELETE not only deleted rows but also removed physical
tuples that were deleted in 1. Missing dead rows were pruned by HOT.

-- 
Itagaki Takahiro


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