Hello David,
from what I understand, in PostgreSQL, tables are stored in one or more files called segments. There is no separation
bycolumns.
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
cacheif there is enough space. This means a table with only one large column large_a takes up less page cache compared
toa table with many large columns large_a and large_b, even though in both cases only large_a is selected.
Is that more or less correct? Ignoring toast?
Tim S.
---- On Mon, 05 Jun 2023 14:58:21 +0200 David G. Johnston wrote ---
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> On Monday, June 5, 2023, Tim Schwenke tim@trallnag.com> wrote:
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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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> Shared buffers is a page cache.
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> David J.
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