Re: Does PostgreSQL cache all columns of a table after SELECT?

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От David G. Johnston
Тема Re: Does PostgreSQL cache all columns of a table after SELECT?
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Msg-id CAKFQuwa-KCHhYi5Z5LKBK+H2H84G7S-dZVqZy-AH3gRUanexnA@mail.gmail.com
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Ответ на Re: Does PostgreSQL cache all columns of a table after SELECT?  (Tim Schwenke <tim@trallnag.com>)
Ответы Re: Does PostgreSQL cache all columns of a table after SELECT?  (Tim Schwenke <tim@trallnag.com>)
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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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