On Sun, Aug 7, 2016 at 10:49:45AM -0400, Bruce Momjian wrote: > OK, crazy idea time --- what if we only do WARM chain additions when all > indexed values are increasing (with NULLs higher than all values)? (If > a key is always-increasing, it can't match a previous value in the > chain.) That avoids the problem of having to check the WARM chain, > except for the previous tuple, and the problem of pruning removing > changed rows. It avoids having to check the index for matching key/ctid > values, and it prevents CREATE INDEX from having to index WARM chain > values. > > Any decreasing value would cause a normal tuple be created.
Actually, when we add the first WARM tuple, we can mark the HOT/WARM chain as either all-incrementing or all-decrementing. We would need a bit to indicate that. Also, it would be possible for keys involved in multi-key indexes to not match the direction of the chain as long as keys earlier in the index matched, e.g. key (1,5,6) would be less than (2,1,1) since 1 < 2, even though 5 > 1. I am not sure it would be worth detecting this. -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + As you are, so once was I. As I am, so you will be. + + Ancient Roman grave inscription + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
