On Wed, 11 Jul 2018 14:26:03 +0300 Alexander Korotkov <a.korot...@postgrespro.ru> wrote: > On Wed, Jul 11, 2018 at 12:04 PM Yugo Nagata <nag...@sraoss.co.jp> wrote: > > When we specify column names for ANALYZE, only the statistics for those > > columns > > are collected. Similarly, is it useful if we have a option to specify an > > index > > for ANALYZE to collect only the statistics for expression in the specified > > index? > > > > A usecase I suppose is that when a new expression index is created and that > > we need only the statistics for the new index. Although ANALYZE of all the > > indexes > > is usually fast because ANALYZE uses a random sampling of the table rows, > > ANALYZE > > on the specific index may be still useful if there are other index whose > > "statistics > > target" is large and/or whose expression takes time to compute, for example. > > > > Attached is the WIP patch to allow to specify a index name as ANALYZE > > parameter. > > Any documatation is not yet included. I would appreciate any feedback! > > I think this makes sense. Once we can collect statistics individually > for regular columns, we should be able to do the same for indexed > expression. Please, register this patch on the next commitfest.
Thank you for your comment! I registered this to CF 2018-09. > Regarding current implementation I found message "ANALYZE option must > be specified when a column list is provided" to be confusing. > Perhaps, you've missed some negation in this message, since in fact > you disallow analyze with column list. > > However, since multicolumn index may contain multiple expression, I > think we should support specifying columns for ANALYZE index clause. > We could support specifying columns by their numbers in the same way > we did for "ALTER INDEX index ALTER COLUMN colnum SET STATISTICS > number". Make sense. I'll fix the patch to support specifying columns of index. Thanks, -- Yugo Nagata <nag...@sraoss.co.jp>
