Tomas Vondra <tomas.von...@2ndquadrant.com> writes: > On Tue, Jan 14, 2020 at 03:12:21PM -0500, Tom Lane wrote: >> cc'ing Tomas in case he has any thoughts about it.
> Well, I certainly do thoughts about this - it's pretty much exactly what > I proposed yesterday in this thread: > > https://www.postgresql.org/message-id/flat/20200113230008.g67iyk4cs3xbnjju@development > The third part of that patch series is exactly about supporting extended > statistics on expressions, about the way you described here. The current > status of the WIP patch is that grammar + ANALYZE mostly works, but > there is no support in the planner. It's obviously still very hackish. Cool. We should probably take the discussion to that thread, then. > I'm also wondering if we could/should 100% rely on extended statistics, > because those are really meant to track correlations between columns, Yeah, it seems likely to me that the infrastructure for this would be somewhat different --- the user-facing syntax could be basically the same, but ultimately we want to generate entries in pg_statistic not pg_statistic_ext_data. Or at least entries that look the same as what you could find in pg_statistic. regards, tom lane
