Обсуждение: Allow to specify a index name as ANALYZE parameter
Hi, 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! Regards, -- Yugo Nagata <nagata@sraoss.co.jp>
Вложения
Hi! On Wed, Jul 11, 2018 at 12:04 PM Yugo Nagata <nagata@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. 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". ------ Alexander Korotkov Postgres Professional: http://www.postgrespro.com The Russian Postgres Company
On Wed, 11 Jul 2018 14:26:03 +0300 Alexander Korotkov <a.korotkov@postgrespro.ru> wrote: > On Wed, Jul 11, 2018 at 12:04 PM Yugo Nagata <nagata@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 <nagata@sraoss.co.jp>
On 11/07/18 11:04, Yugo Nagata wrote: > A usecase I suppose is that when a new expression index is created and that > we need only the statistics for the new index. I wonder if this shouldn't just be done automatically. -- Vik Fearing +33 6 46 75 15 36 http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support
On 7/12/18, Yugo Nagata <nagata@sraoss.co.jp> wrote: > On Wed, 11 Jul 2018 14:26:03 +0300 > Alexander Korotkov <a.korotkov@postgrespro.ru> wrote: >> 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. Hi, I'm interested in this feature, so I've signed up to help review. Given the above, I thought it appropriate to mark the patch Waiting on Author. -John Naylor > Thanks, > > -- > Yugo Nagata <nagata@sraoss.co.jp> > >
On Sun, Sep 09, 2018 at 01:25:49PM +0700, John Naylor wrote: > I'm interested in this feature, so I've signed up to help review. > Given the above, I thought it appropriate to mark the patch Waiting on > Author. I find this feature interesting as well. The patch has been waiting on author input for a couple of weeks unfortunately, so I am marking as returned with feedback. Could you update the patch? -- Michael