Allow references to columns in UPDATE statements (#472)

Allow references to columns in UPDATE statements

Queries like "UPDATE tbl SET column = column + 1" are now allowed, so long as you don't use any IMMUTABLE functions.

src/backend/distributed/planner/multi_router_planner.c

@@ -272,7 +272,7 @@ ErrorIfModifyQueryNotSupported(Query *queryTree)
 				continue;
 			}
 
-			if (!IsA(targetEntry->expr, Const))
+			if (contain_mutable_functions((Node *) targetEntry->expr))
 			{
 				hasNonConstTargetEntryExprs = true;
 			}
@@ -354,8 +354,8 @@ ErrorIfModifyQueryNotSupported(Query *queryTree)
 	if (hasNonConstTargetEntryExprs || hasNonConstQualExprs)
 	{
 		ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-						errmsg("cannot plan sharded modification containing values "
-							   "which are not constants or constant expressions")));
+						errmsg("functions used in modification queries on distributed "
+							   "tables must be marked IMMUTABLE")));
 	}
 
 	if (specifiesPartitionValue)

src/test/regress/expected/multi_modifications.out

@@ -155,16 +155,16 @@ SET client_min_messages TO DEFAULT;
 -- commands with non-constant partition values are unsupported
 INSERT INTO limit_orders VALUES (random() * 100, 'ORCL', 152, '2011-08-25 11:50:45',
 								 'sell', 0.58);
-ERROR:  cannot plan sharded modification containing values which are not constants or constant expressions
+ERROR:  functions used in modification queries on distributed tables must be marked IMMUTABLE
 -- commands with expressions that cannot be collapsed are unsupported
 INSERT INTO limit_orders VALUES (2036, 'GOOG', 5634, now(), 'buy', random());
-ERROR:  cannot plan sharded modification containing values which are not constants or constant expressions
+ERROR:  functions used in modification queries on distributed tables must be marked IMMUTABLE
 -- commands with mutable functions in their quals
 DELETE FROM limit_orders WHERE id = 246 AND bidder_id = (random() * 1000);
-ERROR:  cannot plan sharded modification containing values which are not constants or constant expressions
+ERROR:  functions used in modification queries on distributed tables must be marked IMMUTABLE
 -- commands with mutable but non-volatilte functions(ie: stable func.) in their quals
 DELETE FROM limit_orders WHERE id = 246 AND placed_at = current_timestamp;
-ERROR:  cannot plan sharded modification containing values which are not constants or constant expressions
+ERROR:  functions used in modification queries on distributed tables must be marked IMMUTABLE
 -- commands with multiple rows are unsupported
 INSERT INTO limit_orders VALUES (DEFAULT), (DEFAULT);
 ERROR:  cannot perform distributed planning for the given modification
@@ -317,6 +317,27 @@ WITH deleted_orders AS (INSERT INTO limit_orders DEFAULT VALUES RETURNING *)
 UPDATE limit_orders SET symbol = 'GM';
 ERROR:  cannot perform distributed planning for the given modification
 DETAIL:  Common table expressions are not supported in distributed modifications.
+SELECT symbol, bidder_id FROM limit_orders WHERE id = 246;
+ symbol | bidder_id 
+--------+-----------
+ GM     |        18
+(1 row)
+
+-- updates referencing just a var are supported
+UPDATE limit_orders SET bidder_id = id WHERE id = 246;
+-- updates referencing a column are supported
+UPDATE limit_orders SET bidder_id = bidder_id + 1 WHERE id = 246;
+-- IMMUTABLE functions are allowed
+UPDATE limit_orders SET symbol = LOWER(symbol) WHERE id = 246;
+SELECT symbol, bidder_id FROM limit_orders WHERE id = 246;
+ symbol | bidder_id 
+--------+-----------
+ gm     |       247
+(1 row)
+
+-- updates referencing non-IMMUTABLE functions are unsupported
+UPDATE limit_orders SET placed_at = now() WHERE id = 246;
+ERROR:  functions used in modification queries on distributed tables must be marked IMMUTABLE
 -- cursors are not supported
 UPDATE limit_orders SET symbol = 'GM' WHERE CURRENT OF cursor_name;
 ERROR:  distributed modifications must target exactly one shard

src/test/regress/expected/multi_upsert.out

@@ -223,15 +223,15 @@ DETAIL:  Subqueries are not supported in distributed modifications.
 -- non mutable function call in the SET
 INSERT INTO upsert_test (part_key, other_col) VALUES (1, 1) ON CONFLICT (part_key) DO
 	UPDATE SET other_col = random()::int;
-ERROR:  cannot plan sharded modification containing values which are not constants or constant expressions
+ERROR:  functions used in modification queries on distributed tables must be marked IMMUTABLE
 -- non mutable function call in the WHERE
 INSERT INTO upsert_test (part_key, other_col) VALUES (1, 1) ON CONFLICT (part_key) DO
 	UPDATE SET other_col = 5 WHERE upsert_test.other_col = random()::int;
-ERROR:  cannot plan sharded modification containing values which are not constants or constant expressions
+ERROR:  functions used in modification queries on distributed tables must be marked IMMUTABLE
 -- non mutable function call in the arbiter WHERE
 INSERT INTO upsert_test (part_key, other_col) VALUES (1, 1) ON CONFLICT (part_key)  WHERE part_key = random()::int
 	DO UPDATE SET other_col = 5;
-ERROR:  cannot plan sharded modification containing values which are not constants or constant expressions
+ERROR:  functions used in modification queries on distributed tables must be marked IMMUTABLE
 -- error out on attempt to update the partition key
 INSERT INTO upsert_test (part_key, other_col) VALUES (1, 1) ON CONFLICT (part_key) DO
 	UPDATE SET part_key = 15;

src/test/regress/sql/multi_modifications.sql

@@ -235,5 +235,21 @@ UPDATE limit_orders SET symbol = 'GM' WHERE id = 246 RETURNING *;
 WITH deleted_orders AS (INSERT INTO limit_orders DEFAULT VALUES RETURNING *)
 UPDATE limit_orders SET symbol = 'GM';
 
+SELECT symbol, bidder_id FROM limit_orders WHERE id = 246;
+
+-- updates referencing just a var are supported
+UPDATE limit_orders SET bidder_id = id WHERE id = 246;
+
+-- updates referencing a column are supported
+UPDATE limit_orders SET bidder_id = bidder_id + 1 WHERE id = 246;
+
+-- IMMUTABLE functions are allowed
+UPDATE limit_orders SET symbol = LOWER(symbol) WHERE id = 246;
+
+SELECT symbol, bidder_id FROM limit_orders WHERE id = 246;
+
+-- updates referencing non-IMMUTABLE functions are unsupported
+UPDATE limit_orders SET placed_at = now() WHERE id = 246;
+
 -- cursors are not supported
 UPDATE limit_orders SET symbol = 'GM' WHERE CURRENT OF cursor_name;