Re:Jepsen Disputes MongoDB's Data Consistency Claims
by orf on Sunday May 24, 2020 @01:22PM
(#23293004)
> SELECT most_common_vals
> FROM pg_stats
> WHERE tablename = 'json_test'
> AND attname = 'json_column';
> {"{\"name\": \"john\"}"}
Hmm. Looks like it does though. Not that it makes a damn bit of difference because if you haven't got a functional index (i.e the stats are next to useless) then you're doing a full table scan, and in that case it sounds like you “expect full table scans to always be fast” :)
And sure, the statistics don't help with the query planner, unless you've got a computed column, but again see "I expect full table scans to always be fast" and re-consider the statement "postgres doesn't keep statistics on json columns" given the fact that it actually does, just like any other column.
> FROM pg_stats
> WHERE tablename = 'json_test'
> AND attname = 'json_column';
> {"{\"name\": \"john\"}"}
Hmm. Looks like it does though. Not that it makes a damn bit of difference because if you haven't got a functional index (i.e the stats are next to useless) then you're doing a full table scan, and in that case it sounds like you “expect full table scans to always be fast” :)
And sure, the statistics don't help with the query planner, unless you've got a computed column, but again see "I expect full table scans to always be fast" and re-consider the statement "postgres doesn't keep statistics on json columns" given the fact that it actually does, just like any other column.
Read up indeed!