While reading this thread, I thought of two things I think we could do if this feature was implemented:

 1. Sort large UPDATE/DELETEs so it is done in heap order

This is actually a TODO item. I imagine it would be possible to do something like:

DELETE FROM foo USING (...) ORDER BY ctid;

with this patch to help this case.

 2. Reducing deadlocks in big UPDATE/DELETEs

One problem that sometimes occurs when doing multiple multi-row UPDATEs or DELETEs concurrently is that the transactions end up working on the same rows, but in a different order. One could use an ORDER BY clause to make sure the transactions don't deadlock.

Thoughts?


Regards,
Marko Tiikkaja

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