Re: [HACKERS] like/ilike improvements

ITAGAKI Takahiro wrote:
> Andrew Dunstan <andrew(at)dunslane(dot)net> wrote:
>
>
>> OK, here is a patch that I think incorporates all the ideas discussed
>> (including part of Mark Mielke's suggestion about optimising %_). There
>> is now no special treatment of UTF8 other than its use of a faster
>> NextChar macro.
>>
>
> This is a benchmark result of 1000 loops of
> SELECT count(*) INTO cnt FROM item WHERE i_title LIKE '%BABABABABARIBA%'
> on the table with 10000 rows.
>
> | SQL_ASCII | LATIN1 | UTF8 | EUC_JP
> ---------+-----------+--------+-------+---------
> HEAD | 8017 | 8029 | 16928 | 18213
> Patched | 7899 | 7887 | 9985 | 10370 [ms]
>
> It improved the performance not only for UTF8, but also for other
> multi-byte encodings and a bit for single-byte encodings.
>
>
>

Interesting. I infer from these results that the biggest bang here comes
from abandoning CHAREQ and doing all comparisons byte-wise.

cheers

andrew