Date: Wed, 16 Feb 2022 12:12:38 -0300
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: unmesh.joshi126@gmail.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #17407: trim trims more than expected
Message-ID: <202202161512.tsbczybuwa3i@alvherre.pgsql>
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On 2022-Feb-16, PG Bug reporting form wrote:

> Unexpected output
> 
> demo=# select trim ('nextval(''' from
> substring('nextval(''auth_table_id_seq''::regclass)' from '%#"%_id_seq#"%'
> for '#' ));
>       btrim       
> ------------------
>  uth_table_id_seq

Not a bug.  trim() receives a *set* of characters to remove, not a
*substring* to remove, so the 'a' in 'auth' is matched to the 'a' in
'nextval(' and gets removed.

You can probably achieve what you want by combining substring() with
position() and char_length(), or by using a regular expression in
regexp_replace().

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
"La conclusión que podemos sacar de esos estudios es que
no podemos sacar ninguna conclusión de ellos" (Tanenbaum)