Date: Fri, 19 Jul 2019 20:39:46 +0200
From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: mayank rupareliya <mayankjr03@gmail.com>
Cc: pgsql-performance@lists.postgresql.org
Subject: Re: Searching in varchar column having 100M records
Message-ID: <20190719183946.ls5vmus7ukhbl63w@development>
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On Fri, Jul 19, 2019 at 07:43:26PM +0530, mayank rupareliya wrote:
>Well, you haven't shown us the execution plan, so it's hard to check why
>it did not help much and give you further advice.
>
>
>This is the latest query execution with explain after adding indexing on
>both columns.
>
>Aggregate  (cost=174173.57..174173.58 rows=1 width=8) (actual
>time=65087.657..65087.658 rows=1 loops=1)
>  ->  Bitmap Heap Scan on fields  (cost=1382.56..174042.61 rows=52386
>width=0) (actual time=160.340..65024.533 rows=31857 loops=1)
>        Recheck Cond: ((field)::text = 'Champlin'::text)
>        Heap Blocks: exact=31433
>        ->  Bitmap Index Scan on index_field  (cost=0.00..1369.46
>rows=52386 width=0) (actual time=125.078..125.079 rows=31857 loops=1)
>              Index Cond: ((field)::text = 'Champlin'::text)
>Planning Time: 8.595 ms
>Execution Time: 65093.508 ms
>

That very clearly does not use the index-only scan, so it's not
surprising it's not any faster. You need to find out why the planner
makes that decision.

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services