On 2021-05-28 16:51, Ron wrote:
> On 5/28/21 5:06 PM, Dean Gibson (DB Administrator) wrote:
>> On 2021-05-28 12:38, Ron wrote:
>>> 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.
>
> Did it run in less than 10 hours?
>
The original VACUUM FULL ANALYZE ran in 10 hours. The plain ANALYZE ran
in 88 seconds.