Re: Strangeness with UNIQUE indexes and UTF-8 - Mailing list pgsql-hackers

From Omar Kilani
Subject Re: Strangeness with UNIQUE indexes and UTF-8
Date
Msg-id CA+8F9hgk+qv-YsiGiYgWF1MYTdNsbXy=UmbmzemDHki2BgE1Bg@mail.gmail.com
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In response to Re: Strangeness with UNIQUE indexes and UTF-8  (Chapman Flack <chap@anastigmatix.net>)
List pgsql-hackers
Hey Chap,

Yeah, I understand. Just ruling out the bad hardware scenario.

Plus the next person to Google this will hopefully stumble upon this thread. :)

Regards,
Omar

On Sun, Jun 6, 2021 at 9:36 AM Chapman Flack <chap@anastigmatix.net> wrote:
On 06/06/21 11:08, Omar Kilani wrote:
> I'm running pg_verify_checksums on the cluster, but the database is
> many TB so it'll be a bit.

Index corruption because of a locale change would not be the sort of thing
checksums would detect. Entries would be put into the index in the correct
order according to the old collation. The same entries can be still there,
intact, just fine according to the checksums, only the new collation would
have put them in a different order. Index search algorithms that are fast,
because they assume the entries to be correctly ordered, will skip regions
of the index where the desired key "couldn't possibly be", and if that's
where the old ordering put it, it won't be found.

Regards,
-Chap

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