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Re: Support LIKE with nondeterministic collations

Daniel Verite <daniel@manitou-mail.org>

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From: "Daniel Verite" <daniel@manitou-mail.org>
To: "Jeff Davis" <pgsql@j-davis.com>
Cc: Peter Eisentraut <peter@eisentraut.org>, Robert Haas <robertmhaas@gmail.com>, Pgsql-Hackers <pgsql-hackers@postgresql.org>
Date: 2024-08-01T19:55:55Z
Lists: pgsql-hackers

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  1. Support LIKE with nondeterministic collations

	Jeff Davis wrote:

> >   col LIKE 'smith%' collate "nd"
> > 
> > is equivalent to:
> > 
> >   col >= 'smith' collate "nd" AND col < U&'smith\ffff' collate "nd"
> 
> That logic seems to assume something about the collation. If you have a
> collation that orders strings by their sha256 hash, that would entirely
> break the connection between prefixes and ranges, and it wouldn't work.

Indeed I would not trust this trick to work outside of ICU collations.


Best regards,
-- 
Daniel Vérité
https://postgresql.verite.pro/
Twitter: @DanielVerite