Re: BUG #18959: Name collisions of expression indexes during parallel Index creations on a pratitioned table.

Dilip Kumar <dilipbalaut(at)gmail(dot)com> writes:
> I haven't reviewed the patch itself, but I like the idea. We're now
> consistently using the parent index name for partitioned indexes,
> whether they're named or unnamed indexes. That looks like a great
> improvement. And I think including the partition number of each level
> in the index name significantly enhances its clarity, especially
> within a multi-level partition hierarchy.

Since people seem to think this might be a good way to proceed,
I spent some effort on cleaning up the regression test changes.

While doing that, I decided that applying this behavioral change to
CREATE TABLE LIKE (the original user of generateClonedIndexStmt)
might not be such a hot idea: the regression test changes that
that induced felt less natural than the ones involving partitioned
indexes. Another practical reason is that all the calls for
partitioned indexes will call DefineIndex immediately, so the
race-condition window for some other session to claim the same
index name is barely wider than it was before. But in CREATE TABLE
LIKE, there's considerably more delay, and I think it might even
be possible to construct counterexamples where our own process
could try to create two identically-named indexes if we try to
nail down the index name in generateClonedIndexStmt.

So that leads me to the attached. Excluding CREATE TABLE LIKE
reduces the number of regression-test changes a little, but
there's still a lot of them, implying this is a nontrivial
behavioral change for users. So I feel like this is not
something to squeeze into v18 post-beta-1. I'm thinking it'd
be appropriate for v19 instead. (We could perhaps back-patch
the other SnapshotDirty patch to ameliorate the problem in the
back branches.)

regards, tom lane