Fix write path for zero column tables

src/backend/columnar/cstore_writer.c

@@ -447,7 +447,7 @@ FlushStripe(TableWriteState *writeState)
 	uint32 lastChunkIndex = stripeBuffers->rowCount / chunkRowCount;
 	uint32 lastChunkRowCount = stripeBuffers->rowCount % chunkRowCount;
 	uint64 stripeSize = 0;
-	uint64 stripeRowCount = 0;
+	uint64 stripeRowCount = stripeBuffers->rowCount;
 
 	elog(DEBUG1, "Flushing Stripe of size %d", stripeBuffers->rowCount);
 
@@ -500,12 +500,6 @@ FlushStripe(TableWriteState *writeState)
 		}
 	}
 
-	for (chunkIndex = 0; chunkIndex < chunkCount; chunkIndex++)
-	{
-		stripeRowCount +=
-			stripeSkipList->chunkSkipNodeArray[0][chunkIndex].rowCount;
-	}
-
 	stripeMetadata = ReserveStripe(relation, stripeSize,
 								   stripeRowCount, columnCount, chunkCount,
 								   chunkRowCount);

src/test/regress/expected/am_insert.out

@@ -149,3 +149,65 @@ SELECT * FROM chunk_group_consistency;
 
 DROP TABLE test_toast_row;
 DROP TABLE test_toast_columnar;
+-- Verify metadata for zero column tables.
+-- We support writing into zero column tables, but not reading from them.
+-- We test that metadata makes sense so we can fix the read path in future.
+CREATE TABLE zero_col() USING columnar;
+SELECT alter_columnar_table_set('zero_col', chunk_group_row_limit => 10);
+ alter_columnar_table_set
+---------------------------------------------------------------------
+
+(1 row)
+
+INSERT INTO zero_col DEFAULT VALUES;
+INSERT INTO zero_col DEFAULT VALUES;
+INSERT INTO zero_col DEFAULT VALUES;
+INSERT INTO zero_col DEFAULT VALUES;
+CREATE TABLE zero_col_heap();
+INSERT INTO zero_col_heap DEFAULT VALUES;
+INSERT INTO zero_col_heap DEFAULT VALUES;
+INSERT INTO zero_col_heap DEFAULT VALUES;
+INSERT INTO zero_col_heap DEFAULT VALUES;
+INSERT INTO zero_col_heap SELECT * FROM zero_col_heap;
+INSERT INTO zero_col_heap SELECT * FROM zero_col_heap;
+INSERT INTO zero_col_heap SELECT * FROM zero_col_heap;
+INSERT INTO zero_col_heap SELECT * FROM zero_col_heap;
+INSERT INTO zero_col SELECT * FROM zero_col_heap;
+SELECT relname, stripeid, row_count FROM columnar.stripe a, pg_class b
+WHERE columnar_relation_storageid(b.oid)=a.storageid AND relname = 'zero_col'
+ORDER BY 1,2,3;
+ relname  | stripeid | row_count
+---------------------------------------------------------------------
+ zero_col |        1 |         1
+ zero_col |        2 |         1
+ zero_col |        3 |         1
+ zero_col |        4 |         1
+ zero_col |        5 |        64
+(5 rows)
+
+SELECT relname, stripeid, value_count FROM columnar.chunk a, pg_class b
+WHERE columnar_relation_storageid(b.oid)=a.storageid AND relname = 'zero_col'
+ORDER BY 1,2,3;
+ relname | stripeid | value_count
+---------------------------------------------------------------------
+(0 rows)
+
+SELECT relname, stripeid, chunkid, row_count FROM columnar.chunk_group a, pg_class b
+WHERE columnar_relation_storageid(b.oid)=a.storageid AND relname = 'zero_col'
+ORDER BY 1,2,3,4;
+ relname  | stripeid | chunkid | row_count
+---------------------------------------------------------------------
+ zero_col |        1 |       0 |         1
+ zero_col |        2 |       0 |         1
+ zero_col |        3 |       0 |         1
+ zero_col |        4 |       0 |         1
+ zero_col |        5 |       0 |        10
+ zero_col |        5 |       1 |        10
+ zero_col |        5 |       2 |        10
+ zero_col |        5 |       3 |        10
+ zero_col |        5 |       4 |        10
+ zero_col |        5 |       5 |        10
+ zero_col |        5 |       6 |         4
+(11 rows)
+
+DROP TABLE zero_col;

src/test/regress/sql/am_insert.sql

@@ -103,3 +103,41 @@ SELECT * FROM chunk_group_consistency;
 
 DROP TABLE test_toast_row;
 DROP TABLE test_toast_columnar;
+
+-- Verify metadata for zero column tables.
+-- We support writing into zero column tables, but not reading from them.
+-- We test that metadata makes sense so we can fix the read path in future.
+CREATE TABLE zero_col() USING columnar;
+SELECT alter_columnar_table_set('zero_col', chunk_group_row_limit => 10);
+
+INSERT INTO zero_col DEFAULT VALUES;
+INSERT INTO zero_col DEFAULT VALUES;
+INSERT INTO zero_col DEFAULT VALUES;
+INSERT INTO zero_col DEFAULT VALUES;
+
+CREATE TABLE zero_col_heap();
+INSERT INTO zero_col_heap DEFAULT VALUES;
+INSERT INTO zero_col_heap DEFAULT VALUES;
+INSERT INTO zero_col_heap DEFAULT VALUES;
+INSERT INTO zero_col_heap DEFAULT VALUES;
+
+INSERT INTO zero_col_heap SELECT * FROM zero_col_heap;
+INSERT INTO zero_col_heap SELECT * FROM zero_col_heap;
+INSERT INTO zero_col_heap SELECT * FROM zero_col_heap;
+INSERT INTO zero_col_heap SELECT * FROM zero_col_heap;
+
+INSERT INTO zero_col SELECT * FROM zero_col_heap;
+
+SELECT relname, stripeid, row_count FROM columnar.stripe a, pg_class b
+WHERE columnar_relation_storageid(b.oid)=a.storageid AND relname = 'zero_col'
+ORDER BY 1,2,3;
+
+SELECT relname, stripeid, value_count FROM columnar.chunk a, pg_class b
+WHERE columnar_relation_storageid(b.oid)=a.storageid AND relname = 'zero_col'
+ORDER BY 1,2,3;
+
+SELECT relname, stripeid, chunkid, row_count FROM columnar.chunk_group a, pg_class b
+WHERE columnar_relation_storageid(b.oid)=a.storageid AND relname = 'zero_col'
+ORDER BY 1,2,3,4;
+
+DROP TABLE zero_col;