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From: David G. Johnston <[email protected]>
To: Tim Schwenke <[email protected]>
Cc: Pgsql Novice <[email protected]>
Subject: Re: Does PostgreSQL cache all columns of a table after SELECT?
Date: Mon, 5 Jun 2023 07:26:08 -0700
Message-ID: <CAKFQuwa-KCHhYi5Z5LKBK+H2H84G7S-dZVqZy-AH3gRUanexnA@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<CAKFQuwamUDxtmA3G4mUP1y4DvntoJ4EA4o02465dfiRO3O9rBQ@mail.gmail.com>
	<[email protected]>

On Mon, Jun 5, 2023, 06:17 Tim Schwenke <[email protected]> wrote:

> Hello David,
>
> from what I understand, in PostgreSQL, tables are stored in one or more
> files called segments. There is no separation by columns.
>
> https://www.postgresql.org/docs/8.1/storage.html
>
> This means if I select a single column from a table the first time, the
> full file / segment is read and put into page cache if there is enough
> space.


Pages are subsegment.

You may also wish to take care to notice the version of documentation pages
you look at and reference.  8.1 is long past its expiration date.

David J.

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