Re: Can get GiST RECHECK clause to work

"Mark Cave-Ayland" <m.cave-ayland@webbased.co.uk> writes:
> I'm trying to mark a GiST index as lossy using the RECHECK operator as
> part of some work on PostGIS, but what happens is that the original
> operator function is never reapplied to the results of the index scan.

You sure?  I'm pretty sure that a number of the contrib gist index
opclasses would fail their regression tests if this were broken.

As of 7.5 you cannot see the reapplication in the generated plan's
filter condition; perhaps that got you confused?

2004-01-05 23:31  tgl
* src/: backend/executor/nodeIndexscan.c,backend/nodes/copyfuncs.c,
backend/nodes/outfuncs.c,backend/optimizer/path/costsize.c,backend/optimizer/plan/createplan.c,backend/optimizer/plan/setrefs.c,
include/nodes/execnodes.h,include/nodes/plannodes.h:Instead of rechecking lossy indexoperators by putting them into the
regularqpqual ('filtercondition'), add special-purpose code to nodeIndexscan.c to recheckthem.  This ends being almost
nonet addition of code, because theremoval of planner code balances out the extra executor code, butit is significantly
moreefficient when a lossy operator isinvolved in an OR indexscan.  The old implementation had to recheckthe entire
indexqualin such cases.
 

        regards, tom lane