On 12/12/2018 16:57, Tom Lane wrote: > Attached is a draft patch for same. It adds storage to pg_statistic > to record the collation of each statistics "slot". A plausible > alternative design would be to just say "look at the collation of the > underlying column", but that would require extra catcache lookups in > the selectivity functions that need the info.
That looks like a good approach to me. > Doing it like this also > makes it theoretically feasible to track stats computed with respect > to different collations for the same column, though I'm not really > convinced that we'd ever do that. It's a good option to keep around. Maybe someday extended statistics could be used to ask for additional statistics to be collected. > * Probably this conflicts to some extent with Peter's "Reorganize > collation lookup" patch, but I haven't studied that yet. I've looked it over, and it's nothing that can't be easily fixed up. In fact, it simplifies a few things, so I'm in favor of moving your patch along first. -- Peter Eisentraut http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
