Re: Adding a '--two-phase' option to 'pg_createsubscriber' utility.

Hi Shubham.

Here are my review comments for v6-0001.

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1.
+# Verify that the subtwophase is enabled ('e') in the pg_subscription catalog
+$node_s->poll_query_until('postgres',
+ "SELECT count(1) = 2 FROM pg_subscription WHERE subtwophasestate = 'e';")
+ or die "Timed out while waiting for subscriber to enable twophase";
+

This form of the SQL is probably OK but it's a bit tricky; Probably it
should have been explained in the comment about where that count "2"
has come from.

~~

I think it was OK as before (v5) to be querying until nothing was NOT
'e'. In other words, until everything was enabled 'e'.
SELECT count(1) = 0 FROM pg_subscription WHERE subtwophasestate NOT IN ('e');

~~

OTOH, to save execution time we really would be satisfied with both
'p' and 'e' states here. (we don't strictly need to wait for the
transition from 'p' to 'e' to occur).

So, SQL like the one below might be the best:

# Verify that all subtwophase states are pending or enabled,
# e.g. there are no subscriptions where subtwophase is disabled ('d').
SELECT count(1) = 0 FROM pg_subscription WHERE subtwophasestate IN ('d')

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Kind Regards,
Peter Smith.
Fujitsu Australia