Re: Shared detoast Datum proposal

From: Nikita Malakhov <hukutoc(at)gmail(dot)com>
To: Andy Fan <zhihuifan1213(at)163(dot)com>
Cc: Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, Michael Zhilin <m(dot)zhilin(at)postgrespro(dot)ru>, Peter Smith <smithpb2250(at)gmail(dot)com>, vignesh C <vignesh21(at)gmail(dot)com>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: Shared detoast Datum proposal
Date: 2024-02-26 07:12:16
Message-ID: CAN-LCVMU_AzYNDQ-MgX3xc5qCnhTgO1LWKUCygOu3neBM-y94g@mail.gmail.com
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Hi!

I see this to be a very promising initiative, but some issues come into my
mind.
When we store and detoast large values, say, 1Gb - that's a very likely
scenario,
we have such cases from prod systems - we would end up in using a lot of
shared
memory to keep these values alive, only to discard them later. Also,
toasted values
are not always being used immediately and as a whole, i.e. jsonb values are
fully
detoasted (we're working on this right now) to extract the smallest value
from
big json, and these values are not worth keeping in memory. For text values
too,
we often do not need the whole value to be detoasted and kept in memory.

What do you think?

--
Regards,
Nikita Malakhov
Postgres Professional
The Russian Postgres Company
https://postgrespro.ru/

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