Re: AWS forcing PG upgrade from v9.6 a disaster

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?

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