Change default replication factor to one

Took the quick-and-dirty approach of changing it back to two during
test runs. Can update tests to expect one in due time.

src/backend/distributed/master/master_node_protocol.c

@@ -64,7 +64,7 @@
 
 /* Shard related configuration */
 int ShardCount = 32;
-int ShardReplicationFactor = 2; /* desired replication factor for shards */
+int ShardReplicationFactor = 1; /* desired replication factor for shards */
 int ShardMaxSize = 1048576;     /* maximum size in KB one shard can grow to */
 int ShardPlacementPolicy = SHARD_PLACEMENT_ROUND_ROBIN;
 

src/backend/distributed/shared_library_init.c

@@ -369,7 +369,7 @@ RegisterCitusConfigVariables(void)
 					 "configuration value at sharded table creation time, "
 					 "and later reuse the initially read value."),
 		&ShardReplicationFactor,
-		2, 1, 100,
+		1, 1, 100,
 		PGC_USERSET,
 		0,
 		NULL, NULL, NULL);

src/test/regress/pg_regress_multi.pl

@@ -219,6 +219,7 @@ push(@pgOptions, '-c', "citus.max_running_tasks_per_node=4");
 push(@pgOptions, '-c', "citus.expire_cached_shards=on");
 push(@pgOptions, '-c', "citus.task_tracker_delay=10ms");
 push(@pgOptions, '-c', "citus.remote_task_check_interval=1ms");
+push(@pgOptions, '-c', "citus.shard_replication_factor=2");
 
 # Add externally added options last, so they overwrite the default ones above
 for my $option (@userPgOptions)