Andres Freund <andres@2ndquadrant.com> writes:
> On 2014-07-11 11:20:08 -0400, Tom Lane wrote:
>> If you're talking about SnapshotNow hazards, I think the risk would be
>> minimal, and probably no worse than cases that the system will cause
>> by itself.
> Yes, SnapshotNow. I could reproduce it causing 'spurious' HOT updates
> and missing index inserts a while back. And I don't think it's
> comparable with normal modifications. Those either have a modification
> blocking lock or use heap_inplace...
I still think the risk is minimal, but if the OP was worried about this
he could take out an AccessExclusive lock on the parent table for long
enough to commit the pg_index change.
regards, tom lane