From: Tom Lane <tgl@sss.pgh.pa.us>
To: Adrian Klaver <adrian.klaver@aklaver.com>
cc: Marcos Pegoraro <marcos@f10.com.br>,
        pgsql-general <pgsql-general@postgresql.org>
Subject: Re: Trying to understand pg_get_expr()
In-reply-to: <5179b412-2eaa-4c96-89f3-53c2fb10dd31@aklaver.com>
References: <ddb9b483-d1fc-4380-84ce-fff20e35893e@aklaver.com> <CAB-JLwZdyUfnC047MzV9woskWH2dToNJEudR34AD8WprEn8Cig@mail.gmail.com> <114fe468-204a-43a9-8edc-26ffd6d598a4@aklaver.com> <CAB-JLwbwKi6q_fG7ByGRJe-L+m9Nx+WHiTP0qhEw7qKzv37QQA@mail.gmail.com> <5179b412-2eaa-4c96-89f3-53c2fb10dd31@aklaver.com>
Comments: In-reply-to Adrian Klaver <adrian.klaver@aklaver.com>
	message dated "Tue, 17 Mar 2026 13:36:34 -0700"
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Date: Tue, 17 Mar 2026 17:04:50 -0400
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Adrian Klaver <adrian.klaver@aklaver.com> writes:
>     adrelid    | pg_typeof |        pg_get_expr
>  --------------+-----------+---------------------------
>   default_test | text      | 'test'::character varying
>   default_test | text      | 0

> Why is the second case not?:
> '0'::integer

PG's parser automatically attributes type integer to an unadorned
integer literal, so no cast is necessary there, and pg_get_expr
doesn't add one.  But an unadorned string like 'test' does not
have a determinate type (well, it has type "unknown", but that
is an implementation artifact).  We emit a cast construct to show
what type the constant was resolved as.

The bigger picture here is that pg_get_expr relies on the same
code that is used for purposes like dumping views.  We want the
output to be such that subexpressions of a view will certainly
be parsed as the same type they were interpreted as before.

			regards, tom lane