MDEV-8755 Equal field propagation is not performed any longer for the IN list when multiple comparison types

mysql-test/r/func_in.result

@@ -812,3 +812,27 @@ EXECUTE s;
 1
 DROP TABLE t1;
 # End of 5.3 tests
+#
+# MDEV-8755 Equal field propagation is not performed any longer for the IN list when multiple comparison types
+#
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1),(2);
+# Ok to propagate equalities into the left IN argument in case of a single comparison type
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE a=1 AND a IN (1,2,3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` = 1)
+# Ok to propagate equalities into IN () list, even if multiple comparison types
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE a=1 AND 1 IN (1,a,'3');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` = 1)
+# Not Ok to propagate equalities into the left IN argument in case of multiple comparison types
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE a=1 AND a IN (1,2,'3');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` = 1) and (`test`.`t1`.`a` in (1,2,'3')))
+DROP TABLE t1;

mysql-test/t/func_in.test

@@ -606,3 +606,16 @@ EXECUTE s;
 DROP TABLE t1;
 
 --echo # End of 5.3 tests
+
+--echo #
+--echo # MDEV-8755 Equal field propagation is not performed any longer for the IN list when multiple comparison types
+--echo #
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1),(2);
+--echo # Ok to propagate equalities into the left IN argument in case of a single comparison type
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE a=1 AND a IN (1,2,3);
+--echo # Ok to propagate equalities into IN () list, even if multiple comparison types
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE a=1 AND 1 IN (1,a,'3');
+--echo # Not Ok to propagate equalities into the left IN argument in case of multiple comparison types
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE a=1 AND a IN (1,2,'3');
+DROP TABLE t1;

sql/item_cmpfunc.h

@@ -1438,18 +1438,18 @@ public:
   Item* propagate_equal_fields(THD *thd, const Context &ctx, COND_EQUAL *cond)
   {
     /*
-      TODO: enable propagation of the args[i>0] arguments even if
-      !arg_types_compatible. See MDEV-8755.
       Note, we pass ANY_SUBST, this makes sure that non of the args
       will be replaced to a zero-filled Item_string.
       Such a change would require rebuilding of cmp_items.
     */
-    if (arg_types_compatible)
+    Context cmpctx(ANY_SUBST, m_compare_type,
-      Item_args::propagate_equal_fields(thd,
+                   Item_func_in::compare_collation());
-                                        Context(ANY_SUBST,
+    for (uint i= 0; i < arg_count; i++)
-                                                m_compare_type,
+    {
-                                                compare_collation()),
+      if (arg_types_compatible || i > 0)
-                                        cond);
+        args[i]->propagate_equal_fields_and_change_item_tree(thd, cmpctx,
+                                                             cond, &args[i]);
+    }
     return this;
   }
   virtual void print(String *str, enum_query_type query_type);