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From: Andrus <[email protected]>
To: pgsql-general <[email protected]>
Subject: How to use index in simple select
Date: Sat, 29 Nov 2025 00:57:46 +0200
Message-ID: <[email protected]> (raw)

Hi!

Table has index on name column:

         CREATE TABLE firma2.klient
         (
             kood character(12) primary key,
              nimi character(100),
            ...
         );

        CREATE INDEX IF NOT EXISTS klient_nimi_idx
         ON firma2.klient USING btree
         (nimi COLLATE pg_catalog."default" ASC NULLS LAST)
         TABLESPACE pg_default;

Database settings have default values:

     enable_indexonlyscan       on
     enable_indexscan           on
     enable_indexonlyscan       on
     enable_indexscan           on

Query

     SELECT * FROM firma2.klient WHERE nimi='John';

Runs slowly.

     analyze firma2.klient;
     explain analyze select * from firma2.klient where nimi='John'

Shows that index is not used:

     "Seq Scan on klient  (cost=0.00..2287976.20 rows=1 width=4002) 
(actual time=12769.987..12769.988 rows=0 loops=1)"
     "  Filter: (nimi = 'John'::bpchar)"
     "  Rows Removed by Filter: 849971"
     "Planning Time: 4.751 ms"
     "Execution Time: 12770.029 ms"

How to force Postgres to use index? It probably worked long time but 
suddenly stopped working today.
Re-started whole windows server but problem persists.

Using

PostgreSQL 17.5 on x86_64-windows, compiled by msvc-19.43.34808, 64-bit

in Windows Server 2022 vers 21H2

Andrus.


Posted also in

https://stackoverflow.com/questions/79832965/how-to-use-index-in-simple-select

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