On 22 December 2017 at 14:29, Robert Haas <robertmh...@gmail.com> wrote: > On Thu, Dec 21, 2017 at 6:53 PM, David Rowley > <david.row...@2ndquadrant.com> wrote: >> Are you considering some sort of clauselist_selectivity() estimate on >> the given parameters and comparing that to the same selectivities that >> were determined for the previous custom plans? > > No, I don't think comparing to previous custom plans is a workable > approach. I was thinking, rather, that if we know for example that > we've doing pruning on partition_column = $1, then we know that only > one partition will match. That's probably a common case. If we've > got partition_column > $1, we could assume that, say, 75% of the > partitions would match. partition_column BETWEEN $1 and $2 is > probably a bit more selective, so maybe we assume 50% of the > partitions would match.
Okay. Do you think this is something we need to solve for this patch? When I complained originally I didn't quite see any way to even test the majority of this patch with the regression tests, but Beena has since proven me wrong about that. -- David Rowley http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
