Re: How to boost performance of ilike queries ?

On Tue, 25 Jan 2005 07:23 pm, Antony Paul wrote:
> Creating an index and using lower(column) does not change the explain
> plan estimates.
> It seems that it is not using index for like or ilike queries
> irrespective of whether it have a pattern matching character in it or
> not. (using PostgreSQL 7.3.3)
>
> On googling I found this thread
>
> http://archives.postgresql.org/pgsql-sql/2004-11/msg00285.php
>
> It says that index is not used if the search string begins with a % symbol.

What exactly are the type of like queries you are going?  there is a solution
for having the % at the start, but you can win everyway.

>
> rgds
> Antony Paul
>
> On Mon, 24 Jan 2005 20:58:54 +1100, Russell Smith <mr-russ@pws.com.au> wrote:
> > On Mon, 24 Jan 2005 08:18 pm, Antony Paul wrote:
> > > Hi,
> > >     I have a query which is executed using ilike. The query values are
> > > received from user and it is executed using PreparedStatement.
> > > Currently all queries are executed as it is using iilike irrespective
> > > of whether it have a pattern matching character or not. Can using =
> > > instead of ilike boot performance ?.  If creating index can help then
> > > how the index should be created on lower case or uppercase ?.
> > >
> > It depends on the type of queries you are doing.
> >
> > changing it to something like  lower(column) like lower('text%'), and
> > creating an index on lower(column) will give you much better performance.
> >
> > If you have % in the middle of the query, it will still be slow, but I assume that is not
> > the general case.
> >
> > I am not sure what the effect of it being prepared will be, however I've had much success
> > with the method above without the queries being prepared.  Others may be able to offer advice
> > about if prepare will effect it.
> >
> > Regards
> >
> > Russell Smith
> >
>
>