Simplify the logical worker type checks by using the switch on worker type.

The current code uses if/else statements at various places to take worker
specific actions. Change those to use the switch on worker type added by
commit 2a8b40e368. This makes code easier to read and understand.

Author: Peter Smith
Reviewed-by: Amit Kapila, Hou Zhijie
Discussion: http://postgr.es/m/CAHut+PttPSuP0yoZ=9zLDXKqTJ=d0bhxwKaEaNcaym1XqcvDEg@mail.gmail.com

src/backend/replication/logical/launcher.c

@@ -468,39 +468,44 @@ retry:
 	bgw.bgw_start_time = BgWorkerStart_RecoveryFinished;
 	snprintf(bgw.bgw_library_name, MAXPGPATH, "postgres");
 
-	if (is_parallel_apply_worker)
+	switch (worker->type)
 	{
+		case WORKERTYPE_APPLY:
+			snprintf(bgw.bgw_function_name, BGW_MAXLEN, "ApplyWorkerMain");
+			snprintf(bgw.bgw_name, BGW_MAXLEN,
+					 "logical replication apply worker for subscription %u",
+					 subid);
+			snprintf(bgw.bgw_type, BGW_MAXLEN, "logical replication apply worker");
+			break;
+
+		case WORKERTYPE_PARALLEL_APPLY:
 			snprintf(bgw.bgw_function_name, BGW_MAXLEN, "ParallelApplyWorkerMain");
 			snprintf(bgw.bgw_name, BGW_MAXLEN,
 					 "logical replication parallel apply worker for subscription %u",
 					 subid);
 			snprintf(bgw.bgw_type, BGW_MAXLEN, "logical replication parallel worker");
-	}
+
-	else if (is_tablesync_worker)
+			memcpy(bgw.bgw_extra, &subworker_dsm, sizeof(dsm_handle));
-	{
+			break;
+
+		case WORKERTYPE_TABLESYNC:
 			snprintf(bgw.bgw_function_name, BGW_MAXLEN, "TablesyncWorkerMain");
 			snprintf(bgw.bgw_name, BGW_MAXLEN,
 					 "logical replication tablesync worker for subscription %u sync %u",
 					 subid,
 					 relid);
 			snprintf(bgw.bgw_type, BGW_MAXLEN, "logical replication tablesync worker");
-	}
+			break;
-	else
+
-	{
+		case WORKERTYPE_UNKNOWN:
-		snprintf(bgw.bgw_function_name, BGW_MAXLEN, "ApplyWorkerMain");
+			/* Should never happen. */
-		snprintf(bgw.bgw_name, BGW_MAXLEN,
+			elog(ERROR, "unknown worker type");
-				 "logical replication apply worker for subscription %u",
-				 subid);
-		snprintf(bgw.bgw_type, BGW_MAXLEN, "logical replication apply worker");
 	}
 
 	bgw.bgw_restart_time = BGW_NEVER_RESTART;
 	bgw.bgw_notify_pid = MyProcPid;
 	bgw.bgw_main_arg = Int32GetDatum(slot);
 
-	if (is_parallel_apply_worker)
-		memcpy(bgw.bgw_extra, &subworker_dsm, sizeof(dsm_handle));
-
 	if (!RegisterDynamicBackgroundWorker(&bgw, &bgw_handle))
 	{
 		/* Failed to start worker, so clean up the worker slot. */

src/backend/replication/logical/tablesync.c

@@ -649,18 +649,29 @@ process_syncing_tables_for_apply(XLogRecPtr current_lsn)
 void
 process_syncing_tables(XLogRecPtr current_lsn)
 {
+	switch (MyLogicalRepWorker->type)
+	{
+		case WORKERTYPE_PARALLEL_APPLY:
+
 			/*
-	 * Skip for parallel apply workers because they only operate on tables
+			 * Skip for parallel apply workers because they only operate on
-	 * that are in a READY state. See pa_can_start() and
+			 * tables that are in a READY state. See pa_can_start() and
 			 * should_apply_changes_for_rel().
 			 */
-	if (am_parallel_apply_worker())
+			break;
-		return;
 
-	if (am_tablesync_worker())
+		case WORKERTYPE_TABLESYNC:
 			process_syncing_tables_for_sync(current_lsn);
-	else
+			break;
+
+		case WORKERTYPE_APPLY:
 			process_syncing_tables_for_apply(current_lsn);
+			break;
+
+		case WORKERTYPE_UNKNOWN:
+			/* Should never happen. */
+			elog(ERROR, "Unknown worker type");
+	}
 }
 
 /*

src/backend/replication/logical/worker.c

@@ -485,10 +485,12 @@ ReplicationOriginNameForLogicalRep(Oid suboid, Oid relid,
 static bool
 should_apply_changes_for_rel(LogicalRepRelMapEntry *rel)
 {
-	if (am_tablesync_worker())
+	switch (MyLogicalRepWorker->type)
-		return MyLogicalRepWorker->relid == rel->localreloid;
-	else if (am_parallel_apply_worker())
 	{
+		case WORKERTYPE_TABLESYNC:
+			return MyLogicalRepWorker->relid == rel->localreloid;
+
+		case WORKERTYPE_PARALLEL_APPLY:
 			/* We don't synchronize rel's that are in unknown state. */
 			if (rel->state != SUBREL_STATE_READY &&
 				rel->state != SUBREL_STATE_UNKNOWN)
@@ -499,11 +501,18 @@ should_apply_changes_for_rel(LogicalRepRelMapEntry *rel)
 						 errdetail("Cannot handle streamed replication transactions using parallel apply workers until all tables have been synchronized.")));
 
 			return rel->state == SUBREL_STATE_READY;
-	}
+
-	else
+		case WORKERTYPE_APPLY:
 			return (rel->state == SUBREL_STATE_READY ||
 					(rel->state == SUBREL_STATE_SYNCDONE &&
 					 rel->statelsn <= remote_final_lsn));
+
+		case WORKERTYPE_UNKNOWN:
+			/* Should never happen. */
+			elog(ERROR, "Unknown worker type");
+	}
+
+	return false;				/* dummy for compiler */
 }
 
 /*