On Wed, Sep 14, 2016 at 12:17 PM, Robert Haas <robertmh...@gmail.com> wrote: > For instance, one idea to grow memory usage incrementally would be to > store dead tuple information separately for each 1GB segment of the > relation. So we have an array of dead-tuple-representation objects, > one for every 1GB of the relation. If there are no dead tuples in a > given 1GB segment, then this pointer can just be NULL. Otherwise, it > can point to either the bitmap representation (which will take ~4.5MB) > or it can point to an array of TIDs (which will take 6 bytes/TID). > That could handle an awfully wide variety of usage patterns > efficiently; it's basically never worse than what we're doing today, > and when the dead tuple density is high for any portion of the > relation it's a lot better.
If you compress the list into a bitmap a posteriori, you know the number of tuples per page, so you could encode the bitmap even more efficiently. It's not a bad idea, one that can be slapped on top of the multiarray patch - when closing a segment, it can be decided whether to turn it into a bitmap or not. -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers