From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Shaheed Haque <shaheedhaque(at)gmail(dot)com> |
Cc: | pgsql-general(at)lists(dot)postgresql(dot)org |
Subject: | Re: JSONB index not in use, but is TOAST the real cause of slow query? |
Date: | 2022-05-28 19:59:12 |
Message-ID: | 3127818.1653767952@sss.pgh.pa.us |
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Lists: | pgsql-general |
Shaheed Haque <shaheedhaque(at)gmail(dot)com> writes:
> One last thought about TOAST. If the cost of the -> retrieving the
> data cannot be obviated, is there any way to tweak how that works?
The only thing that's readily tweakable is to disable data compression
for the out-of-line values (see ALTER TABLE ... SET STORAGE, and note
that you have to rebuild the table for already-stored values to be
changed). It seems unlikely that that will help you much though,
since doing that would save CPU at the cost of more disk I/O, and
it seems that the I/O side is your bottleneck already. It *would*
help if jsonb had logic for partial fetches, because that'd require
uncompressed storage to work. But AFAICS that's not there yet.
I distinctly recall that that was planned for when we were designing
jsonb's on-disk layout, but I see no code actually doing anything
of that sort ... the -> operator certainly doesn't.
regards, tom lane
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