Re: Functions and Indexes

On Tue, 2024-11-19 at 11:53 +0100, Moreno Andreo wrote:
> > > What about if query becomes
> > > SELECT foo1, foo2 FROM bar WHERE (POSITION(foo1 IN 'blah blah') >0)
> >
> > You could create an index like
> >
> >     CREATE INDEX ON bar (position(foo1 IN 'blah blah'));
> >
> > Alternatively, you could have a partial index:
> >
> >     CREATE INDEX ON bar (foo1) INCLUDE (foo2)
> >     WHERE position(foo1 IN 'blah blah') > 0;
>
> Interesting. Never seen this form, I'll look further on it.
>
> I stumbled into
> https://www.cybertec-postgresql.com/en/indexing-like-postgresql-oracle/
> and discovered text_pattern_ops.
> I'm wondering if it can be of any use in my index, that should hold a
> WHERE condition with a combination of LIKE and the POSITION expression
> above.
> More docs to read ... :-)

I don't think "text_pattern_ops" will help here - queries that use LIKE
to search for a substring (LIKE '%string%') cannot make use of a b-tree
index.

Yours,
Laurenz Albe