Re: query planner: automatic rescribe of LIKE to BETWEEN ?

Thomas Samson wrote:
> On 8/22/06, Alvaro Herrera <alvherre(at)commandprompt(dot)com> wrote:
> >Ulrich Habel wrote:
> >> Hello all,
> >> had an idea of optimizing a query that may work generally.
> >>
> >> In case a 'column' is indexed, following two alterations could be done
> >> I think:
> >>
> >> A)
> >>
> >> select ... where column ~ '^Foo' --> Seq Scan
> >
> >This is not true. You can make this query use an index if you create it
> >with opclass varchar_pattern_ops or text_pattern_ops, as appropiate.
> >
> >Thus you don't need any hack here.
> >
>
> And in the case of more general expression, like:
> select ... where column ~ 'something';
>
> Is there a way to optimise this ? (in the case where 'something' is not
> a word, but a part of a word)

Not sure. I'd try tsearch2 or pg_trgm (or pg_tgrm, whatever it's
called). It's trigram indexing.

--
Alvaro Herrera http://www.CommandPrompt.com/
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