pg_stats avg_width and null_frac
Started by Paul McGarryalmost 8 years ago2 messagesgeneral
Can anyone confirm that the "avg_width" reported in the pg_stats is the
avg_width not including any null rows?
ie if a field had:
avg_width: 6
null_frac: 0.5
Then
- 50% of the rows would be empty for this field
- The other 50% of the rows would have data with an avg_width of 6 bytes?
(according to the sampled data at least)
Paul
Re: pg_stats avg_width and null_frac
On Tue, Jun 5, 2018 at 5:49 PM, Paul McGarry <paul@paulmcgarry.com> wrote:
Can anyone confirm that the "avg_width" reported in the pg_stats is the
avg_width not including any null rows?
Yes.
https://github.com/postgres/postgres/blob/master/src/include/catalog/pg_statistic.h#L40
It actually is documented but only on the underlying catalog, not the view.
https://www.postgresql.org/docs/10/static/catalog-pg-statistic.html
David J.