Fix command counter increment bug

Fixes citusdata/citus#714

On `InsertShardRow`, we previously called `CommandCounterIncrement()` before
`CitusInvalidateRelcacheByRelid(relationId);`. This might prevent to skip
invalidation of the distributed table in the next access within the same session.

src/backend/distributed/commands/create_distributed_table.c

@@ -16,6 +16,7 @@
 #include "access/htup.h"
 #include "access/htup_details.h"
 #include "access/nbtree.h"
+#include "access/xact.h"
 #include "catalog/dependency.h"
 #include "catalog/index.h"
 #include "catalog/indexing.h"
@@ -299,6 +300,8 @@ master_create_distributed_table(PG_FUNCTION_ARGS)
 
 	RecordDistributedRelationDependencies(distributedRelationId, distributionKey);
 
+	CommandCounterIncrement();
+
 	heap_close(pgDistPartition, NoLock);
 	relation_close(distributedRelation, NoLock);
 

src/backend/distributed/master/master_metadata_utility.c

@@ -357,11 +357,12 @@ InsertShardRow(Oid relationId, uint64 shardId, char storageType,
 
 	simple_heap_insert(pgDistShard, heapTuple);
 	CatalogUpdateIndexes(pgDistShard, heapTuple);
-	CommandCounterIncrement();
 
-	/* close relation and invalidate previous cache entry */
-	heap_close(pgDistShard, RowExclusiveLock);
+	/* invalidate previous cache entry and close relation */
 	CitusInvalidateRelcacheByRelid(relationId);
+
+	CommandCounterIncrement();
+	heap_close(pgDistShard, RowExclusiveLock);
 }
 
 
@@ -397,9 +398,8 @@ InsertShardPlacementRow(uint64 shardId, char shardState, uint64 shardLength,
 
 	simple_heap_insert(pgDistShardPlacement, heapTuple);
 	CatalogUpdateIndexes(pgDistShardPlacement, heapTuple);
-	CommandCounterIncrement();
 
-	/* close relation */
+	CommandCounterIncrement();
 	heap_close(pgDistShardPlacement, RowExclusiveLock);
 }
 
@@ -440,13 +440,14 @@ DeleteShardRow(uint64 shardId)
 	distributedRelationId = pgDistShardForm->logicalrelid;
 
 	simple_heap_delete(pgDistShard, &heapTuple->t_self);
-	CommandCounterIncrement();
 
 	systable_endscan(scanDescriptor);
-	heap_close(pgDistShard, RowExclusiveLock);
 
 	/* invalidate previous cache entry */
 	CitusInvalidateRelcacheByRelid(distributedRelationId);
+
+	CommandCounterIncrement();
+	heap_close(pgDistShard, RowExclusiveLock);
 }
 
 
@@ -500,9 +501,9 @@ DeleteShardPlacementRow(uint64 shardId, char *workerName, uint32 workerPort)
 	}
 
 	simple_heap_delete(pgDistShardPlacement, &heapTuple->t_self);
-	CommandCounterIncrement();
-
 	systable_endscan(scanDescriptor);
+
+	CommandCounterIncrement();
 	heap_close(pgDistShardPlacement, RowExclusiveLock);
 }