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From: Andrew Gierth <andrew@tao11.riddles.org.uk>
To: pgsql-hackers@postgresql.org
Subject: parseCheckAggregates vs. assign_query_collations
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Precedence: bulk

Looking into a bug report on the -general list about grouping sets,
which turns out to be an issue of collation assignment: if the query has

  CASE GROUPING(expr) WHEN 1 ...

then the expression is rejected as not matching the one in the GROUP BY
clause, because CASE already assigned collations to the expression (as a
special case in its transform function) while the rest of the query
hasn't yet had them assigned, because parseCheckAggregates gets run
before assign_query_collations.

I'll be looking into this in detail later, but right now, cam anyone
think of any reason why parseCheckAggregates couldn't be moved to after
assign_query_collations?

-- 
Andrew (irc:RhodiumToad)