| From: | David Rowley <dgrowleyml(at)gmail(dot)com> |
|---|---|
| To: | Peter Geoghegan <pg(at)bowt(dot)ie> |
| Cc: | "Dirschel, Steve" <steve(dot)dirschel(at)thomsonreuters(dot)com>, "pgsql-general(at)lists(dot)postgresql(dot)org" <pgsql-general(at)lists(dot)postgresql(dot)org>, "Wong, Kam Fook (TR Technology)" <kamfook(dot)wong(at)thomsonreuters(dot)com> |
| Subject: | Re: Query performance going from Oracle to Postgres |
| Date: | 2023-09-07 10:48:06 |
| Message-ID: | CAApHDvrR18bk9qkfBpcAnFRpp5JZ0C0=iVXkOxAxD+aWwk8LEQ@mail.gmail.com |
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| Lists: | pgsql-general |
On Thu, 7 Sept 2023 at 19:17, Peter Geoghegan <pg(at)bowt(dot)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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