Enable Werror for all warnings

Changes to ruleutils match changes made upstream to silence gcc fallthrough warnings

src/backend/distributed/commands/multi_copy.c

@@ -1288,6 +1288,7 @@ ConversionPathForTypes(Oid inputType, Oid destType, CopyCoercionData *result)
 		case COERCION_PATH_NONE:
 		{
 			ereport(ERROR, (errmsg("cannot cast %d to %d", inputType, destType)));
+			return;
 		}
 
 		case COERCION_PATH_ARRAYCOERCE:
@@ -1308,10 +1309,10 @@ ConversionPathForTypes(Oid inputType, Oid destType, CopyCoercionData *result)
 				ereport(ERROR, (errmsg("can not run query which uses an implicit coercion"
 									   " between array types")));
 			}
-
-			/* fallthrough */
 		}
 
+		/* fallthrough */
+
 		case COERCION_PATH_COERCEVIAIO:
 		{
 			result->coercionType = COERCION_PATH_COERCEVIAIO;

src/backend/distributed/executor/multi_executor.c

@@ -273,7 +273,6 @@ ReturnTupleFromTuplestore(CitusScanState *scanState)
 void
 LoadTuplesIntoTupleStore(CitusScanState *citusScanState, Job *workerJob)
 {
-	CustomScanState customScanState = citusScanState->customScanState;
 	List *workerTaskList = workerJob->taskList;
 	TupleDesc tupleDescriptor = NULL;
 	ListCell *workerTaskCell = NULL;

src/backend/distributed/relay/relay_event_utility.c

@@ -29,6 +29,15 @@
 #include "catalog/namespace.h"
 #include "catalog/pg_class.h"
 #include "catalog/pg_constraint.h"
+
+#if PG_VERSION_NUM < 110000
+
+/* pg_constraint_fn.h is gone in postgres 11,
+ * get_relation_constraint_oid is merged into pg_constraint.h then
+ */
+#include "catalog/pg_constraint_fn.h"
+#endif
+
 #include "distributed/commands.h"
 #include "distributed/metadata_cache.h"
 #include "distributed/relay_utility.h"

src/backend/distributed/utils/citus_clauses.c

@@ -83,6 +83,8 @@ PartiallyEvaluateExpression(Node *expression, PlanState *planState)
 			}
 		}
 
+		/* fallthrough */
+
 		case T_FuncExpr:
 		case T_OpExpr:
 		case T_DistinctExpr:

src/backend/distributed/utils/metadata_cache.c

@@ -625,17 +625,20 @@ LookupNodeForGroup(int32 groupId)
 		{
 			ereport(ERROR, (errmsg("node group %d does not have a primary node",
 								   groupId)));
+			return NULL;
 		}
 
 		case USE_SECONDARY_NODES_ALWAYS:
 		{
 			ereport(ERROR, (errmsg("node group %d does not have a secondary node",
 								   groupId)));
+			return NULL;
 		}
 
 		default:
 		{
 			ereport(FATAL, (errmsg("unrecognized value for use_secondary_nodes")));
+			return NULL;
 		}
 	}
 }

src/backend/distributed/utils/ruleutils_10.c

@@ -4528,8 +4528,8 @@ isSimpleNode(Node *node, Node *parentNode, int prettyFlags)
 					return false;
 				}
 				/* else do the same stuff as for T_SubLink et al. */
-				/* FALL THROUGH */
 			}
+			/* FALLTHROUGH */
 
 		case T_SubLink:
 		case T_NullTest:

src/backend/distributed/utils/ruleutils_11.c

@@ -4530,8 +4530,8 @@ isSimpleNode(Node *node, Node *parentNode, int prettyFlags)
 					return false;
 				}
 				/* else do the same stuff as for T_SubLink et al. */
-				/* FALL THROUGH */
 			}
+			/* FALLTHROUGH */
 
 		case T_SubLink:
 		case T_NullTest: