From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alex Zeng <Alex.Zeng@datam.co.nz>
cc: "pgsql-bugs@lists.postgresql.org" <pgsql-bugs@lists.postgresql.org>
Subject: Re: information_schema.constraint_column_usage shows wrong table name
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Comments: In-reply-to Alex Zeng <Alex.Zeng@datam.co.nz>
	message dated "Tue, 10 Aug 2021 02:57:00 -0000"
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Date: Tue, 10 Aug 2021 11:51:23 -0400
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Alex Zeng <Alex.Zeng@datam.co.nz> writes:
> When creating a constraint from table A to table B, the table name and c=
olumn name in information_schema.constraint_column_usage  shows table B. T=
hat makes impossible to check whether a constraint exists as we can have a=
 constraint from table C to B and they will have same value in information=
_schema.constraint_column_usage.

The SQL standard says the purpose of this view is to

    Identify the columns used by referential constraints, unique
    constraints, check constraints, and assertions defined in this catalog
    and owned by a given user or role.

so I think the view is showing the column name it is supposed to,
ie the referenced column name not the referencing column name.
The key_column_usage view might help you with the other thing.

			regards, tom lane