On 07/17/2012 12:41 PM, David Johnston wrote:
So the question that needs to be asked is what kind of performance increase can be had during DML (insert/update) statements and whether those gains are worth pursuing. Since these other engines appear to allow both cases you should be able to get at least a partial idea of the performance gains between "index (a,b,c,d)" and "index (a,b) covering (c,d)".
Tom's recent answer to me on this point (as I understood it) was that he would expect performance to degrade, not improve, since the btree code is known not to perform well when there are many non-unique values.
cheers andrew -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers