From: Tom Lane <tgl@sss.pgh.pa.us>
To: Shrikant Bhende <shrikantpostgresql@gmail.com>
cc: Jeff Janes <jeff.janes@gmail.com>,
        Avinash Kumar <avinash.vallarapu@gmail.com>,
        dbatoCloud Solution <dbatocloud17@gmail.com>,
        pgsql-admin@lists.postgresql.org
Subject: Re: Query taking seq scan on a table
In-reply-to: 
 <CAMTQpJCguViOXL5kY=h90u40iS3MkRzLS39umnNYcQDLoFZ9oA@mail.gmail.com>
References: 
 <CAMTQpJA7eNEXJuLk=Yu5ubo0Wp8xYRwFzzpghRshDYCYPmJHJQ@mail.gmail.com>
 <CAN0TujdziL1CD7FFwKogObZSoe-b1rLLHUPc9m-H+GNbLm5naQ@mail.gmail.com>
 <CAMTQpJCrPLcbw6vmR2i8S6qbXVG3bLioTG7aCBm1JkBHoFtmrw@mail.gmail.com>
 <CAN0TujdQdT=H2EUAQLXzC0Pkc+zhoFyXFj3ayA4t4uz4sokPnw@mail.gmail.com>
 <CAMTQpJBgo03JVO1fRnmMDqsqQZJ-NsuubRL3EyXjKj4UU0v0YQ@mail.gmail.com>
 <CAMkU=1zeEd2Q1yLKBDaKC1DW1UVxtYJiAX+ifp6mwodTOGqCnw@mail.gmail.com>
 <CAMTQpJCguViOXL5kY=h90u40iS3MkRzLS39umnNYcQDLoFZ9oA@mail.gmail.com>
Comments: In-reply-to Shrikant Bhende <shrikantpostgresql@gmail.com>
	message dated "Tue, 22 Sep 2020 18:29:19 +0530"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <1176450.1600783646.1@sss.pgh.pa.us>
Date: Tue, 22 Sep 2020 10:07:26 -0400
Message-ID: <1176451.1600783646@sss.pgh.pa.us>
Precedence: bulk

Shrikant Bhende <shrikantpostgresql@gmail.com> writes:
> *create index concurrently lname_test_btree_txt_pat_ops on wldbowner.member
> (lname text_pattern_ops) where fname like LOWER(unaccent_string(lname) ||
> '%')*
> Is this the correct way to create a b-tree index with text_pattern_ops for
> my requirement ?

No.  What you're trying to optimize is

                            Filter: ((lower(unaccent_string((lname)::text))
~~ 'info%'::text) AND (lower(unaccent_string((fname)::text)) ~~
'travel%'::text))

so you need one or both of

create index on member (lower(unaccent_string(lname)) text_pattern_ops);
create index on member (lower(unaccent_string(fname)) text_pattern_ops);

If one of those two conditions is reliably more selective than the
other, perhaps just one index would do.

			regards, tom lane