Fix inadequacies in recently added wait events

In commit 9915de6c1cb2, we introduced a new wait point for replication
slots and incorrectly labelled it as wait event PG_WAIT_LOCK.  That's
wrong, so invent an appropriate new wait event instead, and document it
properly.

While at it, fix numerous other problems in the vicinity:
- two different walreceiver wait events were being mixed up in a single
  wait event (which wasn't documented either); split it out so that they
  can be distinguished, and document the new events properly.

- ParallelBitmapPopulate was documented but didn't exist.

- ParallelBitmapScan was not documented (I think this should be called
  "ParallelBitmapScanInit" instead.)

- Logical replication wait events weren't documented

- various symbols had been added in dartboard order in various places.
  Put them in alphabetical order instead, as was originally intended.

Discussion: https://postgr.es/m/20170808181131.mu4fjepuh5m75cyq@alvherre.pgsql

2 files changed, 4 insertions, 3 deletions

diff --git a/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
index 93dd7b5c176..de03362c91c 100644
--- a/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
+++ b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
@@ -181,7 +181,7 @@ libpqrcv_connect(const char *conninfo, bool logical, const char *appname,
 							   WL_LATCH_SET | io_flag,
 							   PQsocket(conn->streamConn),
 							   0,
-							   WAIT_EVENT_LIBPQWALRECEIVER);
+							   WAIT_EVENT_LIBPQWALRECEIVER_CONNECT);
 
 		/* Emergency bailout? */
 		if (rc & WL_POSTMASTER_DEATH)
@@ -582,7 +582,7 @@ libpqrcv_PQexec(PGconn *streamConn, const char *query)
 								   WL_LATCH_SET,
 								   PQsocket(streamConn),
 								   0,
-								   WAIT_EVENT_LIBPQWALRECEIVER);
+								   WAIT_EVENT_LIBPQWALRECEIVER_RECEIVE);
 
 			/* Emergency bailout? */
 			if (rc & WL_POSTMASTER_DEATH)
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index 08c0b1b285f..63e1aaa9102 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -391,7 +391,8 @@ retry:
 							name, active_pid)));
 
 		/* Wait here until we get signaled, and then restart */
-		ConditionVariableSleep(&slot->active_cv, PG_WAIT_LOCK);
+		ConditionVariableSleep(&slot->active_cv,
+							   WAIT_EVENT_REPLICATION_SLOT_DROP);
 		ConditionVariableCancelSleep();
 		goto retry;
 	}