On 16 July 2010 14:14, Brendan Jurd <dire...@gmail.com> wrote: > On 16 July 2010 22:51, Richard Huxton <d...@archonet.com> wrote: >> On 16/07/10 13:44, Brendan Jurd wrote:> >>> At this scale we should be seeing around 2 million bytes saved, but >>> instead the tables are identical. Is there some kind of disconnect in >>> how the new short numeric is making it to the disk, or perhaps another >>> effect interfering with my test? >> >> You've probably got rows being aligned to a 4-byte boundary. You're probably >> not going to see any change unless you have a couple of 1-byte columns that >> get placed after the numeric. If you went from 10 bytes down to 8, that >> should be visible. > > Ah, thanks for the hint Richard. I didn't see any change with two > 1-byte columns after the numeric, but with four such columns I did > finally see a difference. > > Test script: > > BEGIN; > > CREATE TEMP TABLE foo (a numeric, b bool, c bool, d bool, e bool); > > INSERT INTO foo (a, b, c, d, e) > SELECT 0::numeric, false, true, i % 2 = 0, i % 2 = 1 > FROM generate_series(1, 1000000) i; > > SELECT pg_total_relation_size('foo'::regclass); > > ROLLBACK; > > Results: > > 8.4: 44326912 > HEAD with patch: 36290560 > > That settles my concern and I'm happy to pass this along to a commiter. > > Cheers, > BJ >
Joy! :) Nice patch Robert. Thom -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers