Re: BUG #1916: selection criteria from one outer join - Mailing list pgsql-bugs

From Kevin Grittner
Subject Re: BUG #1916: selection criteria from one outer join
Date
Msg-id s33a6b5f.085@gwmta.wicourts.gov
Whole thread Raw
List pgsql-bugs
I agree that it looks like "overenthusiastic propagation
of implied equalities."  (Nicely put.)  I haven't tested
whether this fails in any other version (we've moved all
our instances to 8.1beta2 to pound it the best we can),
but I see that Klint Gore has reported the test case fails
in 7.4.7 and 8.0.0.
=20
Any idea on when a fix might be available, or what
conditions must exist in a query for this failure to occur?
If this is too big to fix in 8.1, we would want to try to
identify vulnerable queries proactively, to work around
it somehow.
=20
-Kevin
=20
=20
>>> Tom Lane <tgl@sss.pgh.pa.us> 09/27/05 11:34 PM >>>
"Kevin Grittner" <kevin.grittner@wicourts.gov> writes:
> Obviously, adding an outer join to a query which is already returning rows
> should never reduce the number of rows returned.

I think this is a case of overenthusiastic propagation of implied
equalities.  Do you know offhand if it fails in 8.0.* or earlier
branches?

            regards, tom lane

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