Josh Berkus <j...@agliodbs.com> writes: > On 08/14/2014 04:02 PM, Tom Lane wrote: >> It would be useful to see min/max/avg of pg_column_size() in both >> these cases.
> Well, this is 9.4, so I can do better than that. How about quartiles? > thetype | colsize_distribution > ---------+---------------------------- > json | {1777,1803,1890,1940,4424} > jsonb | {5902,5926,5978,6002,6208} OK. That matches with the observation about being mostly toasted or not --- the threshold for pushing out-of-line would be something a little under 2KB depending on the other columns you had in the table. What's more, it looks like the jsonb data is pretty much never getting compressed --- the min is too high for that. So I'm guessing that this example is mostly about the first_success_by threshold preventing any compression from happening. Please, before looking at my other patch, try this: in src/backend/utils/adt/pg_lzcompress.c, change line 221 thusly: - 1024, /* Give up if no compression in the first 1KB */ + INT_MAX, /* Give up if no compression in the first 1KB */ then reload the jsonb data and give us the same stats on that. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers