Feedback-ID: i76984098:Fastmail
Message-ID: <3093741e-6a84-43e8-a009-fccff8abe998@aklaver.com>
Date: Sat, 29 Nov 2025 09:27:43 -0800
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: How to use index in simple select
To: Andrus <kobruleht2@hot.ee>, pgsql-general <pgsql-general@postgresql.org>
References: <bf6ab185-fb9d-4504-9ddc-61af2e4bc028@hot.ee>
Content-Language: en-US
From: Adrian Klaver <adrian.klaver@aklaver.com>
In-Reply-To: <bf6ab185-fb9d-4504-9ddc-61af2e4bc028@hot.ee>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Archived-At: <https://www.postgresql.org/message-id/3093741e-6a84-43e8-a009-fccff8abe998%40aklaver.com>
Precedence: bulk

On 11/28/25 14:57, Andrus wrote:
> 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
> 
> 

Seems to be already answered:

"It looks like reindex table firma2.klient restored index scan. create 
index concurrently was used when lot of transactions using this table 
where running"


-- 
Adrian Klaver
adrian.klaver@aklaver.com