Re: [HACKERS] bumping HASH_VERSION to 3

On Tue, Apr 11, 2017 at 2:23 PM, Bruce Momjian <bruce@momjian.us> wrote:
> On Fri, Mar 31, 2017 at 02:48:05PM -0400, Tom Lane wrote:
>> +1, as long as we're clear on what will happen when pg_upgrade'ing
>> an installation containing hash indexes.  I think a minimum requirement is
>> that it succeed and be able to start up, and allow the user to manually
>> REINDEX such indexes afterwards.  Bonus points for:
>>
>> 1. teaching pg_upgrade to create a script containing the required REINDEX
>> commands.  (I think it's produced scripts for similar requirements in the
>> past.)
>>
>> 2. marking the index invalid so that the system would silently ignore it
>> until it's been reindexed.  I think there might be adequate infrastructure
>> for that already thanks to REINDEX CONCURRENTLY, and it'd just be a matter
>> of getting pg_upgrade to hack the indexes' catalog state.  (If not, it's
>> probably not worth the trouble.)
>
> We already have code to do all of that, but it was removed from
> pg_upgrade in 9.5.  You can still see it in 9.4:
>
>         contrib/pg_upgrade/version_old_8_3.c::old_8_3_invalidate_hash_gin_indexes()
>
> I would be happy to restore that code and make it work for PG 10.

Cool!

-- 
Robert Haas
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