On Fri, Jun 29, 2012 at 08:10:03AM +0200, Csaba Nagy wrote: > Hi all, > > > On Thu, Jun 28, 2012 at 5:16 AM, David E. Wheeler <da...@justatheory.com> > > wrote: > > I don't see the virtue of this in this case. Since the index is not > > unique, why not just put the index on (a,b,c,d) and be done with it? > > Is there some advantage to be had in inventing a way to store c and d > > in the index without having them usable for indexing? > > Why not restrict it to UNIQUE indexes ? > > For not unique indexes it has no advantages (it could be in fact indexed > on all columns anyway as an implementation detail). > > For the unique case the problem of many identical entries mentioned by > Tom is not relevant, so the additional data will only bloat the index > but not otherwise affect the index performance. > > Would this get close enough to index-covered table ? _That_ would be > interesting - I have a really big table (table/index size: 370G/320G, > ~8*10^9 rows) which is basically using double space because it's primary > key is covering all columns of the table.
I was wondering if there was some way to specify an expression index that did a unique index check on some columns but included more columns not part of the unique index. -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers