Fix pg_relation_size() for non-main forks.

When dispatching the pg_relation_size() call to the segments, we were not
passing through the fork name. As a result, it always calculated the size
of the 'main' fork, regardless of the fork argument.

This has been wrong since the 8.4 merge, which introduced relation forks.

src/backend/utils/adt/dbsize.c

@@ -440,6 +440,7 @@ pg_relation_size(PG_FUNCTION_ARGS)
 {
 	Oid			relOid = PG_GETARG_OID(0);
 	text	   *forkName = PG_GETARG_TEXT_P(1);
+	ForkNumber	forkNumber;
 	Relation	rel;
 	int64		size = 0;
 
@@ -463,17 +464,19 @@ pg_relation_size(PG_FUNCTION_ARGS)
 	if (rel == NULL)
 		PG_RETURN_NULL();
 
+	forkNumber = forkname_to_number(text_to_cstring(forkName));
+
 	if (relOid == 0 || rel->rd_node.relNode == 0)
 		size = 0;
 	else
-		size = calculate_relation_size(rel,
-									   forkname_to_number(text_to_cstring(forkName)));
+		size = calculate_relation_size(rel, forkNumber);
 
 	if (Gp_role == GP_ROLE_DISPATCH)
 	{
 		char	   *sql;
 
-		sql = psprintf("select pg_catalog.pg_relation_size(%u)", relOid);
+		sql = psprintf("select pg_catalog.pg_relation_size(%u, '%s')", relOid,
+					   forkNames[forkNumber]);
 
 		size += get_size_from_segDBs(sql);
 	}

src/test/regress/expected/db_size_functions.out

@@ -149,6 +149,12 @@ select pg_relation_size('heapsizetest') between 3000000 and 5000000; -- 3637248
  t
 (1 row)
 
+select pg_relation_size('heapsizetest', 'fsm') between 250000 and 350000; -- 294912
+ ?column? 
+----------
+ t
+(1 row)
+
 select pg_table_size('heapsizetest') between 3000000 and 5000000; -- 4030464
  ?column? 
 ----------
@@ -216,12 +222,18 @@ CREATE TABLE aosizetest (a int) WITH (appendonly=true, orientation=row);
 NOTICE:  Table doesn't have 'DISTRIBUTED BY' clause -- Using column named 'a' as the Greenplum Database data distribution key for this table.
 HINT:  The 'DISTRIBUTED BY' clause determines the distribution of data. Make sure column(s) chosen are the optimal data distribution key to minimize skew.
 insert into aosizetest select generate_series(1, 100000);
-select pg_relation_size('aosizetest') between 750000 and 1500000; --1001648
+select pg_relation_size('aosizetest') between 750000 and 1500000; -- 1001648
  ?column? 
 ----------
  t
 (1 row)
 
+select pg_relation_size('aosizetest', 'fsm'); -- 0
+ pg_relation_size 
+------------------
+                0
+(1 row)
+
 select pg_table_size('aosizetest') between 1000000 and 1500000; -- 1263792
  ?column? 
 ----------
@@ -256,6 +268,12 @@ select pg_relation_size('aocssizetest') between 1000000 and 2000000; -- 1491240
  t
 (1 row)
 
+select pg_relation_size('aocssizetest', 'fsm'); -- 0
+ pg_relation_size 
+------------------
+                0
+(1 row)
+
 select pg_table_size('aocssizetest') between 1500000 and 3000000; -- 1884456
  ?column? 
 ----------

src/test/regress/sql/db_size_functions.sql

@@ -56,6 +56,7 @@ vacuum heapsizetest;
 
 -- Check that the values are in an expected ranges.
 select pg_relation_size('heapsizetest') between 3000000 and 5000000; -- 3637248
+select pg_relation_size('heapsizetest', 'fsm') between 250000 and 350000; -- 294912
 select pg_table_size('heapsizetest') between 3000000 and 5000000; -- 4030464
 select pg_table_size('heapsizetest') > pg_relation_size('heapsizetest');
 select pg_indexes_size('heapsizetest');
@@ -74,7 +75,8 @@ select pg_total_relation_size('heapsizetest') = pg_table_size('heapsizetest') +
 -- Test on AO and AOCS tables
 CREATE TABLE aosizetest (a int) WITH (appendonly=true, orientation=row);
 insert into aosizetest select generate_series(1, 100000);
-select pg_relation_size('aosizetest') between 750000 and 1500000; --1001648
+select pg_relation_size('aosizetest') between 750000 and 1500000; -- 1001648
+select pg_relation_size('aosizetest', 'fsm'); -- 0
 select pg_table_size('aosizetest') between 1000000 and 1500000; -- 1263792
 select pg_table_size('aosizetest') > pg_relation_size('aosizetest');
 select pg_total_relation_size('aosizetest') between 1000000 and 1500000; -- 1263792
@@ -83,6 +85,7 @@ select pg_total_relation_size('aosizetest') = pg_table_size('aosizetest');
 CREATE TABLE aocssizetest (a int, col1 int, col2 text) WITH (appendonly=true, orientation=column);
 insert into aocssizetest select g, g, 'x' || g from generate_series(1, 100000) g;
 select pg_relation_size('aocssizetest') between 1000000 and 2000000; -- 1491240
+select pg_relation_size('aocssizetest', 'fsm'); -- 0
 select pg_table_size('aocssizetest') between 1500000 and 3000000; -- 1884456
 select pg_table_size('aocssizetest') > pg_relation_size('aocssizetest');
 select pg_total_relation_size('aocssizetest') between 1500000 and 3000000; -- 1884456