Re: Query performance going from Oracle to Postgres - Mailing list pgsql-general

From David Rowley
Subject Re: Query performance going from Oracle to Postgres
Date
Msg-id CAApHDvrR18bk9qkfBpcAnFRpp5JZ0C0=iVXkOxAxD+aWwk8LEQ@mail.gmail.com
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In response to Re: Query performance going from Oracle to Postgres  (Peter Geoghegan <pg@bowt.ie>)
Responses Re: Query performance going from Oracle to Postgres  (Peter Geoghegan <pg@bowt.ie>)
List pgsql-general
On Thu, 7 Sept 2023 at 19:17, Peter Geoghegan <pg@bowt.ie> wrote:
> It seems likely that the problem here is that some of the predicates
> appear as so-called "Filter:" conditions, as opposed to true index
> quals.

hmm, if that were true we'd see "Rows Removed by Filter" in the
explain analyze.

I think all that's going on is that each tuple is on a different page
and the heap accesses are just causing many buffers to be accessed. It
seems to me that an IOS would likely fix that problem which is why I
suggested count(*) instead of
count(<not_null_column_thats_the_only_col_used_thats_not_in_the_index>)

David



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