Re: "reverse()" on strings
От | h012@ied.com |
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Тема | Re: "reverse()" on strings |
Дата | |
Msg-id | no.Yo.N.nN.0208280400360.20016-100000@business.com обсуждение исходный текст |
Ответ на | Re: "reverse()" on strings (Josh Berkus <josh@agliodbs.com>) |
Список | pgsql-sql |
Jeff & Josh, thanks for showing me a solution ! John PS: just curious: is there anything I can do to affect effectiveness of the cache, when ISCACHABLE is used ? (I.e. size / expiring algorithm, or order of inputs - E.g. when building the index, is there anything that would order the inputs first, to maximize cache hit/miss ratio, such as "CREATE INDEX extension_idx ON file (reverse(name)) ORDER BY name" ? On Mon, 26 Aug 2002, Josh Berkus wrote: > Jeff, h012, > > > CREATE FUNCTION fn_strrev(text) returns text as ' > > return reverse($_[0]) > > ' language 'plperl' with (iscachable); > > If you make that "WITH (ISCACHABLE, ISSTRICT)" the index will be faster to > update on columns which contain large numbers of NULLs. "ISSTRICT" refers to > the fact that if the function receives a NULL, it will output a NULL, and > thus saves the parser the time running NULLs through the function. > > Also, remember to use this index, you'll have to call the exact same function > in your queries. > > -- -- Gospel of Jesus is the saving power of God for all who believe -- ## To some, nothing is impossible. ## http://Honza.Vicherek.com/
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