Bug #30520714: MYSQL SERVER RETURNS UNEXPECTED ROWS WHEN USING STORED

               FUNCTIONS IN WHERE CLAUSE

When optimizer extracts conditions on constant tables for early evaluation,
it does not include conditions that are expensive to evaluate
which includes conditions involving stored functions. However,
"make_join_select" wrongly concludes that it can remove the entire
"where condition" when the extracted condition evaluates to true because
it involves only const tables (values are available).

Solution:
Added a check for "expensive conditions" before removing the "where_cond"

Reviewed By: Roy Lyseng <[email protected]>

Author: Chaithra Gopalareddy

mysql-test/r/sp.result

@@ -8385,3 +8385,22 @@ y
 15
 DROP PROCEDURE v1;
 DROP TABLE t1;
+#
+# Bug#30520714 - MYSQL SERVER RETURNS UNEXPECTED ROWS WHEN USING STORED
+#                FUNCTIONS IN WHERE CLAUSE
+#
+CREATE TABLE t1( f1 INT NOT NULL PRIMARY KEY, f2 INT);
+INSERT INTO t1 VALUES (1, 1);
+CREATE FUNCTION ReturnFalse() RETURNS BOOL
+DETERMINISTIC
+BEGIN
+DECLARE result BOOL;
+SET result = FALSE;
+RETURN result;
+END$$
+SELECT IF (COUNT(*) > 0, 'affected', 'not affected') FROM t1
+WHERE f1 = 1 AND f2 AND ReturnFalse();
+IF (COUNT(*) > 0, 'affected', 'not affected')
+not affected
+DROP FUNCTION ReturnFalse;
+DROP TABLE t1;

mysql-test/t/sp.test

@@ -9780,3 +9780,28 @@ DELIMITER ;$$
 CALL v1(3,2);
 DROP PROCEDURE v1;
 DROP TABLE t1;
+
+--echo #
+--echo # Bug#30520714 - MYSQL SERVER RETURNS UNEXPECTED ROWS WHEN USING STORED
+--echo #                FUNCTIONS IN WHERE CLAUSE
+--echo #
+
+CREATE TABLE t1( f1 INT NOT NULL PRIMARY KEY, f2 INT);
+INSERT INTO t1 VALUES (1, 1);
+
+DELIMITER $$;
+
+CREATE FUNCTION ReturnFalse() RETURNS BOOL
+    DETERMINISTIC
+BEGIN
+DECLARE result BOOL;
+    SET result = FALSE;
+    RETURN result;
+END$$
+DELIMITER ;$$
+
+SELECT IF (COUNT(*) > 0, 'affected', 'not affected') FROM t1
+  WHERE f1 = 1 AND f2 AND ReturnFalse();
+
+DROP FUNCTION ReturnFalse;
+DROP TABLE t1;

sql/sql_optimizer.cc

@@ -9179,8 +9179,14 @@ static bool make_join_select(JOIN *join, Item *cond) {
     trace_const_cond.add("condition_on_constant_tables", const_cond)
         .add("condition_value", const_cond_result);
     if (const_cond_result) {
+      /*
+        If all the tables referred by the condition are const tables and
+        if the condition is not expensive, we can remove the where condition
+        as it will always evaluate to "true".
+      */
       if (join->plan_is_const() &&
-          !(cond->used_tables() & ~join->const_table_map)) {
+          !(cond->used_tables() & ~join->const_table_map) &&
+          !cond->is_expensive()) {
         DBUG_PRINT("info", ("Found always true WHERE condition"));
         join->where_cond = NULL;
       }