On 2018-06-18 17:50:44 -0400, Andrew Dunstan wrote: > > > On 06/18/2018 05:46 PM, Jaime Casanova wrote: > > On 18 June 2018 at 16:36, Andrew Dunstan <andrew.duns...@2ndquadrant.com> > > wrote: > > > This is a MySQL feature, where an index is not considered by the planner. > > > Implementing it should be fairly straightforward, adding a new boolean to > > > pg_index, and options to CREATE INDEX and ALTER INDEX. I guess VISIBLE > > > would > > > become a new unreserved keyword. > > > > > > The most obvious use case is to see what the planner does when the index > > > is > > > not visible, for example which other index(es) it might use. There are > > > probably other cases where we might want an index to enforce a constraint > > > but not to be used in query planning. > > > > > > So, do we want this feature? If we do I'll go ahead and prepare a patch. > > > > > should pg_index.indisvalid works for this? in that case you only need > > the syntax for it... > > > > > I thought about that. But I think these are more or less orthogonal. I > doubt it will involve lots of extra code, though.
Be careful about that - currently it's not actually trivially possible to ever update pg_index rows. No, I'm not kidding you. pg_index.indexcheckxmin relies on the pg_index row's xmin. If you have ALTER do a non inplace update, you'll break things. Greetings, Andres Freund
