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From: Igor Korot <[email protected]>
To: Tom Lane <[email protected]>
Cc: David G. Johnston <[email protected]>
Cc: Adrian Klaver <[email protected]>
Cc: pgsql-generallists.postgresql.org <[email protected]>
Subject: Re: Determine server version from psql script
Date: Sun, 23 Mar 2025 12:38:18 -0500
Message-ID: <CA+FnnTztyXpMxEiKTZhxMtcQ8Nm6D+M1jbfJFfkJYU9dyvTeLg@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <CA+FnnTyWEsYi=_QTeSXoGXd7Fkd8C7_AnCc5=hho-DZF9_iunQ@mail.gmail.com>
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	<[email protected]>

Hi, Tom,



On Sat, Mar 22, 2025, 10:01 PM Tom Lane <[email protected]> wrote:

> Igor Korot <[email protected]> writes:
> > On Sat, Mar 22, 2025, 8:58 PM David G. Johnston <
> [email protected]>
> > wrote:
> >> Then read the psql docs.  Your version has \if and you’ll find server
> >> version listed as the available client variables.
>
> > I was hoping for something like
>
> > If server_version >= X:
> >      CREATE OR REPLACE TRIGGER...
>
> psql's \if doesn't (yet) have any native expression evaluation
> ability, so you have to farm out the ">=" comparison.  The
> psql docs suggest relying on the server to do it, which would
> go along the lines of
>
> select current_setting('server_version_num')::int >= 130000 as v13
> \gset
> \if :v13
>    ... do something
> \else
>    ... do something else
> \endif
>

Thank for the code.

2 things, however.
1. Apparently CREATE OR RELACE TRIGGER syntax is available since v17, which
is the current one. So I hadto adjust the numbers.. 😀
2. Is there a way to do CREATE TRIGGER IF NOT EXIST for the earlier version?

Thank you.

>
> You could also do the comparison client-side, along the lines of
>
> \set v13 `expr :SERVER_VERSION_NUM \>= 130000`
> \if :v13
>   ... etc
>
> But that introduces assorted platform dependencies and requires
> close attention to correct shell quoting, so it's seldom
> preferable IMO.
>
>                         regards, tom lane
>


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