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From: Junwang Zhao <[email protected]>
To: [email protected]
To: [email protected]
Subject: Re: BUG #19446: Domain DEFAULT not reflected in system catalogs and information_schema (PG 18.3)
Date: Mon, 30 Mar 2026 23:00:08 +0800
Message-ID: <CAEG8a3+n0GgeJYG5qOFsLY_txKVX8CE5TE_5oE2d0+SjQ9+DzQ@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>

On Mon, Mar 30, 2026 at 7:52 PM PG Bug reporting form
<[email protected]> wrote:
>
> The following bug has been logged on the website:
>
> Bug reference:      19446
> Logged by:          Xianghang Zheng
> Email address:      [email protected]
> PostgreSQL version: 18.3
> Operating system:   Linux x86_64
> Description:
>
> 1. PostgreSQL Version
> PostgreSQL 18.3 (x86_64)
> 2. Operating System
> Linux x86_64
> 3. Problem Description
> When a column uses a domain with DEFAULT value, all system catalogs fail to
> reflect the default:
> - pg_attribute.atthasdef = false
> - No entries in pg_attrdef
> - information_schema.columns.column_default is empty
> But the default value works correctly at runtime.
> This is a metadata bug.
> 4. Steps to Reproduce
> CREATE DOMAIN info_domain AS int DEFAULT 100;
> CREATE TABLE t (col info_domain);
> SELECT attname, atthasdef
> FROM pg_attribute
> WHERE attrelid = 't'::regclass AND attnum > 0;
> SELECT * FROM pg_attrdef WHERE adrelid = 't'::regclass;
> SELECT column_name, column_default
> FROM information_schema.columns
> WHERE table_name = 't' AND column_name = 'col';
> INSERT INTO t DEFAULT VALUES;
> SELECT * FROM t;
> 5. Actual Result
> - atthasdef = f
> - pg_attrdef returns empty
> - column_default is empty
> - But the default value 100 works
> 6. Expected Result
> System catalogs should show the domain's DEFAULT correctly.
> 7. Test Output
> postgres=# CREATE DOMAIN info_domain AS int DEFAULT 100;
> CREATE DOMAIN
> postgres=# CREATE TABLE t (col info_domain);
> CREATE TABLE
> postgres=# SELECT attname, atthasdef FROM pg_attribute WHERE attrelid =
> 't'::regclass AND attnum > 0;
>  attname | atthasdef
> ---------+-----------
>  col     | f
> (1 row)
> postgres=# SELECT * FROM pg_attrdef WHERE adrelid = 't'::regclass;
>  oid | adrelid | adnum | adbin
> -----+---------+-------+-------
> (0 rows)
> postgres=# SELECT column_name, column_default FROM
> information_schema.columns WHERE table_name = 't' AND column_name = 'col';
>  column_name | column_default
> -------------+----------------
>  col         |
> (1 row)
> postgres=# INSERT INTO t DEFAULT VALUES;
> INSERT 0 1
> postgres=# SELECT * FROM t;
>  col
> -----
>  100
> (1 row)
>
>
>
>

Same as your report of bug #19445, this should be by design.


-- 
Regards
Junwang Zhao

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  Subject: Re: BUG #19446: Domain DEFAULT not reflected in system catalogs and information_schema (PG 18.3)
  In-Reply-To: <CAEG8a3+n0GgeJYG5qOFsLY_txKVX8CE5TE_5oE2d0+SjQ9+DzQ@mail.gmail.com>

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