On 5/28/21 1:40 PM, Dean Gibson (DB Administrator) wrote:
On 2021-05-28 08:12, Adrian Klaver wrote:
On 5/27/21 8:41 PM, Dean Gibson (DB Administrator) wrote:
I started to use PostgreSQL v7.3 in 2003 on my home Linux systems (4 at one point), gradually moving to v9.0 w/ replication in 2010. In 2017 I moved my 20GB database to AWS/RDS, gradually upgrading to v9.6, & was entirely satisfied with the result.
In March of this year, AWS announced that v9.6 was nearing end of support, & AWS would forcibly upgrade everyone to v12 on January 22, 2022, if users did not perform the upgrade earlier. My first attempt was successful as far as the upgrade itself, but complex queries that normally ran in a couple of seconds on v9.x, were taking minutes in v12.
Did you run a plain ANALYZE(https://www.postgresql.org/docs/12/sql-analyze.html) on the tables in the new install?
After each upgrade (to 10, 11, 12, & 13), I did a "VACUUM FULL ANALYZE". On 10 through 12, it took about 45 minutes & significant CPU activity, & temporarily doubled the size of the disk space required. As you know, that disk space is not shrinkable under AWS's RDS. On v13, it took 10 hours with limited CPU activity, & actually slightly less disk space required.
Under normal conditions, VACUUM FULL is pointless on a freshly-loaded database; in RDS, it's anti-useful.
That's why Adrian asked if you did a plain ANALYZE.
Just now did. No change in EXPLAIN ANALYZE output.
