Re: todo: Hash index creation
От | Hannu Krosing |
---|---|
Тема | Re: todo: Hash index creation |
Дата | |
Msg-id | 1183366377.6370.4.camel@hannu-laptop обсуждение исходный текст |
Ответ на | Re: todo: Hash index creation (Naz Gassiep <naz@mira.net>) |
Список | pgsql-hackers |
Ühel kenal päeval, E, 2007-07-02 kell 04:27, kirjutas Naz Gassiep: > I've been warned away from hash indexes before, however I had no idea > that it's performance was that abysmal that BTREE beat it and I was > definitely not aware that they were not included in WAL logs. I was told > it wasn't as good as it could be, but I wasn't told it was pretty much > an alpha piece of code. > > As a result, when creating tables containing large blocks of text I wish > to index, I've been using HASH as an index method. If you just wish to have smaller indexes, then you can use functional btree indexes over text hash, like this: CREATE INDEX largetextindex on mytable(hashtext(largetext)); and use SELECT * FROM mytable where hashtext(largetext) = hastext('searchvalue') and largetext = 'searchvalue' ; btw, if the real hash indexes don't get fixes soon, maybe we could redefine hash index to actually mean usage like this and do the rewrites in parser? > Please can we state > in the manual that HASH index types are in a beta stage of development > or something similar, or perhaps remove the manual entry altogether > until HASH is at a point where it is usable in production. > > Regards, > A very surprised n00b. > > ---------------------------(end of broadcast)--------------------------- > TIP 3: Have you checked our extensive FAQ? > > http://www.postgresql.org/docs/faq
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