Thread: best index for ~ ordering?

Hi all, i have a large table with one varchar field, and im triyng to 
get information about what index should i use in order to using that 
index (if this is possible) for ~ searching, and/or using LIKE searching.

Thanks!
Gerardo

On Tue, Mar 06, 2007 at 06:34:23PM -0300, Gerardo Herzig wrote:
> Hi all, i have a large table with one varchar field, and im triyng to 
> get information about what index should i use in order to using that 
> index (if this is possible) for ~ searching, and/or using LIKE searching.

What sort of match are you doing?  If you're doing left-anchored
searches (LIKE 'blah%') then your standard btree is good.  If you're
doing unanchored searches (LIKE '%blah%' or similar) you're best doing
tsearch.  If it's right-anchored, you can do an index on the reverse
of the string.

A 

-- 
Andrew Sullivan  | ajs@crankycanuck.ca
Unfortunately reformatting the Internet is a little more painful 
than reformatting your hard drive when it gets out of whack.    --Scott Morris

Well, im wondering if is possible using LIKE '%blah%', even better would be
upper/lower(string) like '%blah%',

Im not at work right now, i will try it latter and makes you know about
the results of using tsearch indexing.

Thanks a lot, man!
Gerardo
> On Tue, Mar 06, 2007 at 06:34:23PM -0300, Gerardo Herzig wrote:
>> Hi all, i have a large table with one varchar field, and im triyng to
>> get information about what index should i use in order to using that
>> index (if this is possible) for ~ searching, and/or using LIKE
>> searching.
>
> What sort of match are you doing?  If you're doing left-anchored
> searches (LIKE 'blah%') then your standard btree is good.  If you're
> doing unanchored searches (LIKE '%blah%' or similar) you're best doing
> tsearch.  If it's right-anchored, you can do an index on the reverse
> of the string.
>
> A
>
> --
> Andrew Sullivan  | ajs@crankycanuck.ca
> Unfortunately reformatting the Internet is a little more painful
> than reformatting your hard drive when it gets out of whack.
>         --Scott Morris
>
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>


-- 
Gerardo Herzig
Direccion General de Organizacion y Sistemas
Facultad de Medicina
U.B.A.

On Wed, Mar 07, 2007 at 12:28:57AM -0300, gherzig@fmed.uba.ar wrote:
> Well, im wondering if is possible using LIKE '%blah%', even better would be
> upper/lower(string) like '%blah%',

Your better bet then is either to index lower(string) or better, on
insert convert everything to lower().

A

-- 
Andrew Sullivan  | ajs@crankycanuck.ca
The plural of anecdote is not data.    --Roger Brinner