Insufficient description in collation mismatch error

Hi,

I tried applying a collation to a GROUP BY clause without applying the
collation to the corresponding column in the SELECT clause.

postgres=# SELECT things, count(*) FROM stuff GROUP BY things COLLATE "C";
ERROR: column "stuff.things" must appear in the GROUP BY clause or be
used in an aggregate function
LINE 1: SELECT things, count(*) FROM stuff GROUP BY things COLLATE "...

Firstly, does it even make sense for a GROUP BY clause to accept COLLATE?

Even if it does, this error message doesn't explain the problem, being
that the column with the necessary collation doesn't appear in the
SELECT.

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Thom Brown
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