Hello,
This is a pg_upgrade known limitation that has been summarized by Greg
Sabino Mullane on
https://www.endpoint.com/blog/2016/12/07/postgres-statistics-and-pain-of-analyze
this way:
The nominal reason for not copying the data is that the table format may
change from version to version. The real reason is that nobody has
bothered to write the conversion logic yet, for pg_upgrade could
certainly copy the pg_statistics information: the table has not changed
for many years.
Regards
Pierre Forstmann
Le 31/03/2021 à 20:15, Virendra Kumar a écrit :
Hello Team,
I was doing an upgrade of one of our PG (9.6.11 to 11.9) database and
came across the question that what is reason PostgreSQL is not doing
copy of stats and we have to analyze right after upgrade. There are
two situations where this will help when we use this DB as our
enterprise database:
1. If DB is in magnitude of hundreds of TB and we have to do analyze
it might take several hours before we handover this to application
services.
2. We are loosing critical information like most common values and
most common freqs because these values are populated over time when
many-many sessions hit table and queries with different values of a
column.
Any input on this is higly appreciated.
Regards,
Virendra Kumar
