pgsql: Update relation's stats in pg_class during vacuum full.

Update relation's stats in pg_class during vacuum full.

Hash index depends on estimation of numbers of tuples and pages of relations,
incorrect value could be a reason of significantly growing of index. Vacuum
full recreates heap and reindex all indexes before renewal stats. The patch
fixes that, so indexes will see correct values.

Backpatch to v10 only because earlier versions haven't usable hash index and
growing of hash index is a single user-visible symptom.

Author: Amit Kapila
Reviewed-by: Ashutosh Sharma, me
Discussion: https://www.postgresql.org/message-id/flat/20171115232922.5tomkxnw3iq6jsg7@inml.weebeastie.net

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/ad337c76b6f454157982309089c3302fe77c9cbc

Modified Files
--------------
src/backend/commands/cluster.c | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)