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List:       postgresql-sql
Subject:    Re: [SQL] "reverse()" on strings
From:       h012 () ied ! com
Date:       2002-08-28 8:07:53
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 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.
> 
> 

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