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From: Tom Lane <tgl@sss.pgh.pa.us>
To: jian he <jian.universality@gmail.com>
cc: Paul Jungwirth <pj@illuminatedcomputing.com>,
        PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: altering a column's collation leaves an invalid foreign key
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Comments: In-reply-to jian he <jian.universality@gmail.com>
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jian he <jian.universality@gmail.com> writes:
>> * in TryReuseForeignKey, we can pass the information that our primary
>> key old collation is nondeterministic
>> and old collation != new collation to the foreign key constraint.

I have a basic question about this: why are we allowing FKs to be
based on nondeterministic collations at all?  ISTM that that breaks
the assumption that there is exactly one referenced row for any
referencing row.

			regards, tom lane