On 2014-02-15 21:01:07 +0530, Amit Kapila wrote: > >More importantly I don't think doing the compression on > > this level is that interesting. I know Heikki argued for it, but I think > > extending the bitmap that's computed for HOT to cover all columns and > > doing this on a column level sounds much more sensible to me. > > Previously we have tried to do at column boundaries, but the main problem > turned out to be in worst cases where we spend time in extracting values > from tuples based on column boundaries and later found that data is not > compressible.
I think that hugely depends on how you implement it. I think you'd need to have a loop traversing over the both tuples at the same time on the level of heap_deform_tuple(). If you'd use the result to get rid of HeapSatisfiesHOTandKeyUpdate() at the same time I am pretty sure you wouldn't see very high overhead. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
