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Subject: Re: Does PostgreSQL cache all columns of a table after SELECT?
From: William Alves Da Silva <william_silva@unochapeco.edu.br>
In-Reply-To: <1888b7bb7fa.112313046679561.2788161417267896332@trallnag.com>
Date: Mon, 5 Jun 2023 09:19:53 -0300
Cc: pgsql-novice <pgsql-novice@lists.postgresql.org>
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Message-Id: <686C8E94-4B50-40E1-9A5C-6500B47C3622@unochapeco.edu.br>
References: <1888b7bb7fa.112313046679561.2788161417267896332@trallnag.com>
To: Tim Schwenke <tim@trallnag.com>
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Hello Tim,

Can you send the EXPLAIN (BUFFERS, ANALYZE, VERBOSE) of your query? This =
will show you whether the plan is using caching or not.


> On 5 Jun 2023, at 09:15, Tim Schwenke <tim@trallnag.com> wrote:
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> Hello,
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> I have the following table with the following columns:
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> large_a: text (few dozen characters up to a few hundred)
> large_b: text (few dozen characters up to a few hundred)
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> The table has several million rows. The DB is running on a large =
machine.
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> I perform the following query:
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> select large_a from table;
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> The first query takes a few minutes. Afterwards I see that the cache =
in memory has grown. Next query only takes a few seconds.
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> What I want to know:
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> Does the cache also contain large_b? Or is only large_a cached? =
Assumption is that memory is large enough to fit everything.
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>=20
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Regards,
William Alves=