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From: Laurenz Albe <[email protected]>
To: Moreno Andreo <[email protected]>
To: [email protected]
Subject: Re: Functions and Indexes
Date: Tue, 19 Nov 2024 12:34:03 +0100
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
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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

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