2011/1/17 Magnus Hagander <mag...@hagander.net>: > On Mon, Jan 17, 2011 at 06:51, Itagaki Takahiro > <itagaki.takah...@gmail.com> wrote: >> On Mon, Jan 17, 2011 at 04:05, Andy Colson <a...@squeakycode.net> wrote: >>> This is a review of: >>> https://commitfest.postgresql.org/action/patch_view?id=468 >>> >>> Purpose: >>> ======== >>> Equal and not-equal _may_ be quickly determined if their lengths are >>> different. This _may_ be a huge speed up if we don't have to detoast. >> >> We can skip detoast to compare lengths of two text/bytea values >> with the patch, but we still need detoast to compare the contents >> of the values. >> >> If we always generate same toasted byte sequences from the same raw >> values, we don't need to detoast at all to compare the contents. >> Is it possible or not? > > For bytea, it seems it would be possible. > > For text, I think locales may make that impossible. Aren't there > locale rules where two different characters can "behave the same" when > comparing them? I know in Swedish at least w and v behave the same > when sorting (but not when comparing) in some variants of the locale. > > In fact, aren't there cases where the *length test* also fails? I > don't know this for sure, but unless we know for certain that two > different length strings can never be the same *independent of > locale*, this whole patch has a big problem... >
Some string's comparation operations are binary now too. But it is question what will be new with collate support. Regards Pavel Stehule > -- > Magnus Hagander > Me: http://www.hagander.net/ > Work: http://www.redpill-linpro.com/ > > -- > Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-hackers > -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
