Avoid invalid array accesses to partitionFileArray

src/backend/distributed/worker/worker_partition_protocol.c

@@ -917,8 +917,13 @@ FilterAndPartitionTable(const char *filterQuery,
 	if (SPI_processed > 0)
 	{
 		TupleDesc rowDescriptor = SPI_tuptable->tupdesc;
-		partitionColumnIndex = ColumnIndex(rowDescriptor, partitionColumnName);
 
+		if (fileCount == 0)
+		{
+			ereport(ERROR, (errmsg("no partition to read into")));
+		}
+
+		partitionColumnIndex = ColumnIndex(rowDescriptor, partitionColumnName);
 		partitionColumnTypeId = SPI_gettypeid(rowDescriptor, partitionColumnIndex);
 		if (partitionColumnType != partitionColumnTypeId)
 		{
@@ -942,6 +947,7 @@ FilterAndPartitionTable(const char *filterQuery,
 	while (SPI_processed > 0)
 	{
 		int rowIndex = 0;
+
 		for (rowIndex = 0; rowIndex < SPI_processed; rowIndex++)
 		{
 			HeapTuple row = SPI_tuptable->vals[rowIndex];
@@ -964,6 +970,10 @@ FilterAndPartitionTable(const char *filterQuery,
 			if (!partitionKeyNull)
 			{
 				partitionId = (*PartitionIdFunction)(partitionKey, partitionIdContext);
+				if (partitionId == INVALID_SHARD_INDEX)
+				{
+					ereport(ERROR, (errmsg("invalid distribution column value")));
+				}
 			}
 			else
 			{

src/test/regress/expected/intermediate_results.out

@@ -256,6 +256,9 @@ SELECT * FROM squares ORDER BY x;
  5 | 25
 (5 rows)
 
+-- empty shard interval array should raise error
+SELECT worker_hash_partition_table(42,1,'SELECT a FROM generate_series(1,100) AS a', 'a', 23, ARRAY[0]);
+ERROR:  invalid distribution column value
 DROP SCHEMA intermediate_results CASCADE;
 NOTICE:  drop cascades to 5 other objects
 DETAIL:  drop cascades to table interesting_squares

src/test/regress/sql/intermediate_results.sql

@@ -141,4 +141,7 @@ WITH (FORMAT text);
 
 SELECT * FROM squares ORDER BY x;
 
+-- empty shard interval array should raise error
+SELECT worker_hash_partition_table(42,1,'SELECT a FROM generate_series(1,100) AS a', 'a', 23, ARRAY[0]);
+
 DROP SCHEMA intermediate_results CASCADE;