Re: MERGE/SPLIT PARTITIONS issues/questions

On Wed, Aug 26, 2026 at 12:06 PM jian he <jian(dot)universality(at)gmail(dot)com> wrote:
> I believe the original design first tries to lock the partitioned
> table with AccessExclusiveLock.
> Then, later patches incrementally reduce the lock level.
>
> Achieving the same result with ATTACH PARTITION requires the user to scan the
> data out, store it somewhere, and then scan it back in. MERGE/SPLIT PARTITION
> needs only a single scan. If we can lower the lock level on the
> parent table as well
> that would make the feature clearly worthwhile.

One can avoid the second scan by initially added relevant CHECK
constraint to the table, which is going to be the a new partition.
That allow subsequent ALTER TABLE ... ATTACH PARTITION to skip the
scan. Thus, manual procedure can at least avoid blocking reader for
long.

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Regards,
Alexander Korotkov
Supabase