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Date: Sat, 29 Nov 2025 00:57:46 +0200
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To: pgsql-general <pgsql-general@postgresql.org>
From: Andrus <kobruleht2@hot.ee>
Subject: How to use index in simple select
Archived-At: <https://www.postgresql.org/message-id/bf6ab185-fb9d-4504-9ddc-61af2e4bc028%40hot.ee>
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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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    <p>Hi!</p>
    <p>Table has index on name column:<br>
      <br>
      <font face="monospace">        CREATE TABLE firma2.klient<br>
                (<br>
                    kood character(12) primary key,<br>
                     nimi character(100),<br>
                   ...<br>
                );<br>
                <br>
               CREATE INDEX IF NOT EXISTS klient_nimi_idx<br>
                ON firma2.klient USING btree<br>
                (nimi COLLATE pg_catalog."default" ASC NULLS LAST)<br>
                TABLESPACE pg_default;<br>
      </font><br>
      Database settings have default values:<br>
      <br>
      <font face="monospace">    enable_indexonlyscan       on<br>
            enable_indexscan           on<br>
            enable_indexonlyscan       on<br>
            enable_indexscan           on<br>
      </font><br>
      Query <br>
      <br>
      <font face="monospace">    SELECT * FROM firma2.klient WHERE
        nimi='John';<br>
      </font><br>
      Runs slowly.<br>
      <br>
      <font face="monospace">    analyze firma2.klient; <br>
            explain analyze select * from firma2.klient where
        nimi='John'<br>
      </font><br>
      Shows that index is not used:<br>
      <br>
          "Seq Scan on klient  (cost=0.00..2287976.20 rows=1 width=4002)
      (actual time=12769.987..12769.988 rows=0 loops=1)"<br>
          "  Filter: (nimi = 'John'::bpchar)"<br>
          "  Rows Removed by Filter: 849971"<br>
          "Planning Time: 4.751 ms"<br>
          "Execution Time: 12770.029 ms"<br>
      <br>
      How to force Postgres to use index? It probably worked long time
      but suddenly stopped working today.<br>
      Re-started whole windows server but problem persists.<br>
      <br>
      Using<br>
      <br>
      PostgreSQL 17.5 on x86_64-windows, compiled by msvc-19.43.34808,
      64-bit<br>
      <br>
      in Windows Server 2022 vers 21H2</p>
    <p>Andrus.</p>
    <p><br>
    </p>
    <p>Posted also in</p>
    <p><a class="moz-txt-link-freetext" href="https://stackoverflow.com/questions/79832965/how-to-use-index-in-simple-select">https://stackoverflow.com/questions/79832965/how-to-use-index-in-simple-select</a></p>
    <p><br>
    </p>
  </body>
</html>

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