On Jul 15, 2010, at 11:58 AM, Brendan Jurd <dire...@gmail.com> wrote: > On 10 July 2010 00:58, Robert Haas <robertmh...@gmail.com> wrote: >> EnterpriseDB asked me to develop the attached patch to reduce the >> on-disk size of numeric and to submit it for inclusion in PG 9.1. >> After searching the archives, I found a possible design for this by >> Tom Lane based on an earlier proposal by Simon Riggs. > > Hi Robert, > > I'm reviewing this patch for the commitfest, and so far everything in > the patch looks good. Compile and regression tests worked fine. > > However, I was trying to find a simple way to verify that it really > was reducing the on-disk size of compact numeric values and didn't get > the results I was expecting. > > I dropped one thousand numerics with value zero into a table and > checked the on-disk size of the relation with your patch and on a > stock 8.4 instance. In both cases the result was exactly the same. > > Shouldn't the table be smaller with your patch? Or is there something > wrong with my test? > > CREATE TEMP TABLE numeric_short (a numeric); > > INSERT INTO numeric_short (a) > SELECT 0::numeric FROM generate_series(1, 1000) i;
Well, on that test, you'll save only 2000 bytes, which is less than a full block, so there's no guarantee the difference would be noticeable at the relation level. Scale it up by a factor of 10 and the difference should be measurable. You might also look at testing with pg_column_size(). ...Robert -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
