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From: Victor Dobrovolsky <booby.stager@gmail.com>
Date: Sun, 26 May 2024 16:20:10 +0300
Message-ID: <CAJFsatN_5EkCuk8GqUG_1iOD0ON6x4BTeMWU08Jierr5m+GD7Q@mail.gmail.com>
Subject: scalar plpgsql functions and their stability flags
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Good day experts...

Question on scalar plpgsql functions stability flags (immutable, stable)
regarding how it works in sql queries.

It is clear that for immutable/stable functions with constant parameters,
 query planner could/should calculate value in a parse time and use it
directly in query, or at least once per query.

But it is unclear for me what exactly should/can happens when parameters
are bounded not to constant values but to query fields.
In such a case there could be some caching mechanics involved for
parameters combinations and result values.
Like building a hash table for that or something similar.

Can someone give me guidance on this matter.
What limits the usefulness of such a mechanism, if it exists.

Thank you.

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<div dir=3D"ltr">Good day experts...<br><br>Question on scalar plpgsql func=
tions stability flags (immutable, stable) regarding how it works in sql que=
ries.<br><br>It is clear that for immutable/stable functions with constant =
parameters,<br>=C2=A0query planner could/should calculate value in a parse =
time and use it directly in query, or at least once per query.<br><br>But i=
t is unclear for me what exactly should/can happens when parameters are bou=
nded not to constant values but to query fields.<br>In such a case there co=
uld be some caching mechanics involved for parameters combinations and resu=
lt values.<br>Like building a hash table for that or something similar.<br>=
<br>Can someone give me guidance on this matter.<br>What limits the usefuln=
ess of such a mechanism, if it exists.<br><br>Thank you.=C2=A0<br><div><br>=
</div></div>

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