Re: Does PostgreSQL cache all columns of a table after SELECT? - Mailing list pgsql-novice

From Tim Schwenke
Subject Re: Does PostgreSQL cache all columns of a table after SELECT?
Date
Msg-id 1888c20926e.d2fc55ae8791.8729366224157085719@trallnag.com
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In response to Re: Does PostgreSQL cache all columns of a table after SELECT?  ("David G. Johnston" <david.g.johnston@gmail.com>)
List pgsql-novice
Thanks, you all helped me



---- On Mon, 05 Jun 2023 16:26:08 +0200 David G. Johnston <david.g.johnston@gmail.com> wrote ---

On Mon, Jun 5, 2023, 06:17 Tim Schwenke <tim@trallnag.com> 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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