On Sat, Mar 29, 2008 at 3:21 AM, Tom Lane <[EMAIL PROTECTED]> wrote: > I just realized that the patch I applied here > http://archives.postgresql.org/pgsql-committers/2008-03/msg00531.php > for Taiki Yamaguchi's bug report here > http://archives.postgresql.org/pgsql-bugs/2008-03/msg00275.php > really doesn't work. It assumes that an ungrouped aggregate > query can't return more than one row, which is true in straight > SQL ... but it's not true if you consider SRFs in the target list. > CVS HEAD gives the wrong answer for this example in the regression > database: > > regression=# select max(unique1), generate_series(1,3) as g from tenk1 > order by g desc; > max | g > ------+--- > 9999 | 1 > 9999 | 2 > 9999 | 3 > (3 rows) > > because it wrongly supposes it can discard the ORDER BY. > > So, back to the drawing board. I had thought of two approaches to > fixing the problem instead of just dodging it. Plan A was to > apply planagg.c's Aggref->Param substitution inside EquivalenceClasses, > as in the draft patch here: > http://archives.postgresql.org/pgsql-patches/2008-03/msg00388.php > which I didn't entirely like for reasons mentioned in that post. > Plan B was to try to revert to the way sort clause matching was > done pre-8.3, that is have make_sort_from_pathkeys check first > for a matching ressortgroupref tag before it goes looking for equal() > expressions. I had actually tried to do that first but got hung > up on the problem of identifying the correct sort operator --- > just taking the exposed type of the targetlist entry doesn't always > work, because of binary-compatible cases (eg, tlist entry may say > it yields varchar but we need to find the text opclass). Perhaps > thinking a bit harder would yield a solution though. > > Does anyone have comments for or against either of these approaches, > or perhaps a Plan C to consider? > > >
In the past I had seen suggestions (perhaps from you) that we should disallow SRFs in target list... Although not for 8.3, but would this be a good time for 8.4 to deprecate the usage of SRFs in targetlist? Best regards, -- [EMAIL PROTECTED] [EMAIL PROTECTED] gmail | hotmail | indiatimes | yahoo }.com EnterpriseDB http://www.enterprisedb.com Mail sent from my BlackLaptop device
