From: | Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk> |
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To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Aggregate ORDER BY patch |
Date: | 2009-11-16 05:04:50 |
Message-ID: | 87zl6nhyhl.fsf@news-spur.riddles.org.uk |
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Lists: | pgsql-hackers |
>>>>> "Tom" == Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
>> What about error handling? If the user specifies agg(distinct x)
>> where x is not sortable, do we leave it to the planner to detect
>> that (which means not reporting the error position?)
Tom> Well, at the moment there's only going to be a sort-based
Tom> implementation, so I don't object to throwing an error for that
Tom> as soon as possible. OTOH I wouldn't recommend expending a lot
Tom> of code to do it there. I would hope that most of the parser's
Tom> work for this can be shared with the existing support for
Tom> query-level ORDER BY/DISTINCT.
The code already uses transformSortClause for most of the work, but
reusing the existing code for DISTINCT would have required more
refactoring than I was happy with, because transformDistinct etc.
all have error message text which is specific to SELECT DISTINCT etc.
Let's see how it falls out in the next patch.
--
Andrew.
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