On Thu, 5 Jun 2025 at 07:31, Ayush Vatsa <ayushvatsa1810(at)gmail(dot)com> wrote:
> Are these Index Scans executed sequentially (one after the other as the Merge Append requests tuples)?
It's a fairly simple answer: Merge Append does not support parallelism.
> Or are they possibly executed in parallel, in advance, or concurrently in some way?
It's probably not impossible to do something in a future version of
PostgreSQL. We have Gather Merge, which handles executing some
sub-nodes and making sure the results get output in the correct order,
so it doesn't seem impossible that something could be done for Merge
Append. It just does not exist yet.
David