pgsql: Dirty replication slots when using sql interface

Dirty replication slots when using sql interface

When pg_logical_slot_get_changes(...) sets confirmed_flush_lsn to the point at
which replay stopped, it doesn't dirty the replication slot.  So if the replay
didn't cause restart_lsn or catalog_xmin to change as well, this change will
not get written out to disk. Even on a clean shutdown.

If Pg crashes or restarts, a subsequent pg_logical_slot_get_changes(...) call
will see the same changes already replayed since it uses the slot's
confirmed_flush_lsn as the start point for fetching changes. The caller can't
specify a start LSN when using the SQL interface.

Mark the slot as dirty after reading changes using the SQL interface so that
users won't see repeated changes after a clean shutdown. Repeated changes still
occur when using the walsender interface or after an unclean shutdown.

Craig Ringer

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/d851bef2d60ff9345249ff67c053e37fe4b364cc

Modified Files
--------------
src/backend/replication/logical/logicalfuncs.c | 15 ++++++++++
src/test/recovery/Makefile                     |  2 ++
src/test/recovery/t/006_logical_decoding.pl    | 40 ++++++++++++++++++++++++++
3 files changed, 57 insertions(+)