Re: like/ilike improvements

From: Andrew Dunstan <andrew(at)dunslane(dot)net>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: like/ilike improvements
Date: 2007-05-22 16:30:37
Message-ID: 46531AAD.9030209@dunslane.net
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Tom Lane wrote:
> Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
>
>> ... It turns out (according to the analysis) that the
>> only time we actually need to use NextChar is when we are matching an
>> "_" in a like/ilike pattern.
>>
>
> I thought we'd determined that advancing bytewise for "%" was also risky,
> in two cases:
>
> 1. Multibyte character set that is not UTF8 (more specifically, does not
> have a guarantee that first bytes and not-first bytes are distinct)
>

I will review - I thought we had ruled that out.

Which non-UTF8 multi-byte charset would be best to test with?

> 2. "_" immediately follows the "%".
>
>
>

The patch in fact calls NextChar in this case.

cheers

andrew

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