Re: [PG19] ILIKE index scan misses rows with a libc UTF-8 collation on macOS

From: Jeff Davis <pgsql(at)j-davis(dot)com>
To: Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com>, shihao zhong <zhong950419(at)gmail(dot)com>
Cc: pgsql-hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Noah Misch <noah(at)leadboat(dot)com>
Subject: Re: [PG19] ILIKE index scan misses rows with a libc UTF-8 collation on macOS
Date: 2026-10-20 15:26:03
Message-ID: a1c1fac7acab60084188c1485be01fef2bbdea33.camel@j-davis.com
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On Tue, 2026-10-20 at 11:16 +0800, Chao Li wrote:
>
> Not really. On unaffected platforms, an unmatched char originally
> goes through 2 checks, now 4 checks, and the latter two are
> redundant, which adds overhead on unaffected platforms.

The checks are in the planner, trying to extract prefixes for an index
search. Those extra checks are insignificant.

Regards,
Jeff Davis

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