AW: AW: [HACKERS] create index updates nrows statistics

Jan wrote:
> From memory not verified:
>
> Doesn't CREATE INDEX update pg_statistics?
>
No.

> I think it does so
> the faked statistics only cause different joins to happen as
> long as there is no index created immediately after CREATE
> TABLE (HASHJOIN vs. NESTLOOP).
>
No, create index on a newly created table does:
1. set reltuples and relpages of the table to 0
2. set relpages=2 and a calculated reltuples of 2048 or below
on the index depending on how many multy columns

This leads to a rather strange state where reltuples of table <
reltuples of index. It forces seq scans on update and select
of single table. (see E. Mergl's update problem)

Andreas