| From: | Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Atri Sharma <atri(dot)jiit(at)gmail(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: WIP Patch for GROUPING SETS phase 1 |
| Date: | 2014-08-22 23:38:59 |
| Message-ID: | 87wqa0m7ev.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:
Tom> I'm not convinced of that; I think some creative hackery in the
Tom> grammar might be able to deal with this.
Making GROUP BY CUBE(a,b) parse as grouping sets rather than as a
function turned out to be the easy part: give CUBE a lower precedence
than '(' (equal to the one for IDENT and various other unreserved
keywords), and a rule that has an explicit CUBE '(' gets preferred
over one that reduces the CUBE to an unreserved_keyword.
The (relatively minor) ugliness required is mostly in the ruleutils
logic to decide how to output a cube(...) function call in such a way
that it doesn't get misparsed as a grouping set. See my other mail on
that.
--
Andrew (irc:RhodiumToad)
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