Fixed bug mdev-10782.

This bug in the code of Item_ref::build_clone could
cause corruption of items in where conditions.
Also made sure that equality predicates extracted
from multiple equality items to be pushed into
materialized views were cloned.

Author: igorbabaev

mysql-test/r/derived_cond_pushdown.result

@@ -6982,3 +6982,28 @@ drop view v1,v2,v3,v4;
 drop view v_union,v2_union,v3_union,v4_union;
 drop view v_double,v_char,v_decimal;
 drop table t1,t2,t1_double,t2_double,t1_char,t2_char,t1_decimal,t2_decimal;
+#
+# MDEV-10782: condition extracted from a multiple equality
+#             pushed into HAVING
+#
+CREATE TABLE t1 (i int);
+INSERT INTO t1 VALUES (1),(2);
+EXPLAIN EXTENDED
+SELECT *
+FROM ( SELECT * FROM ( SELECT MIN(i) as f FROM t1 ) sq1 ) AS sq2
+WHERE f = 8;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	PRIMARY	<derived3>	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+3	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	
+Warnings:
+Note	1003	select `sq1`.`f` AS `f` from (select min(`test`.`t1`.`i`) AS `f` from `test`.`t1` having (`f` = 8)) `sq1` where (`sq1`.`f` = 8)
+SELECT *
+FROM ( SELECT * FROM ( SELECT MIN(i) as f FROM t1 ) sq1 ) AS sq2
+WHERE f = 8;
+f
+SELECT *
+FROM ( SELECT * FROM ( SELECT MIN(i) as f FROM t1 ) sq1 ) AS sq2
+WHERE f = 1;
+f
+1
+DROP TABLE t1;

mysql-test/t/derived_cond_pushdown.test

@@ -877,4 +877,26 @@ eval explain format=json $query;
 drop view v1,v2,v3,v4;
 drop view v_union,v2_union,v3_union,v4_union;
 drop view v_double,v_char,v_decimal;
-drop table t1,t2,t1_double,t2_double,t1_char,t2_char,t1_decimal,t2_decimal;    
+drop table t1,t2,t1_double,t2_double,t1_char,t2_char,t1_decimal,t2_decimal;  
+
+--echo #
+--echo # MDEV-10782: condition extracted from a multiple equality
+--echo #             pushed into HAVING
+--echo #
+
+CREATE TABLE t1 (i int);
+INSERT INTO t1 VALUES (1),(2);
+EXPLAIN EXTENDED
+SELECT *
+  FROM ( SELECT * FROM ( SELECT MIN(i) as f FROM t1 ) sq1 ) AS sq2
+    WHERE f = 8;
+SELECT *
+  FROM ( SELECT * FROM ( SELECT MIN(i) as f FROM t1 ) sq1 ) AS sq2
+    WHERE f = 8;
+SELECT *
+  FROM ( SELECT * FROM ( SELECT MIN(i) as f FROM t1 ) sq1 ) AS sq2
+    WHERE f = 1;
+DROP TABLE t1;
+
+
+  

sql/item.cc

@@ -2296,10 +2296,16 @@ Item* Item_func_or_sum::build_clone(THD *thd, MEM_ROOT *mem_root)
   if (!copy)
     return 0;
   if (arg_count > 2)
+  {
     copy->args= 
       (Item**) alloc_root(mem_root, sizeof(Item*) * arg_count);
+    if (!copy->args)
+      return 0;
+  }
   else if (arg_count > 0)
     copy->args= copy->tmp_arg;
+
+   
   for (uint i= 0; i < arg_count; i++)
   {
     Item *arg_clone= args[i]->build_clone(thd, mem_root);
@@ -2332,6 +2338,10 @@ Item* Item_ref::build_clone(THD *thd, MEM_ROOT *mem_root)
   Item_ref *copy= (Item_ref *) get_copy(thd, mem_root);
   if (!copy)
     return 0;
+  copy->ref= 
+      (Item**) alloc_root(mem_root, sizeof(Item*));
+  if (!copy->ref)
+      return 0;
   Item *item_clone= (* ref)->build_clone(thd, mem_root);
   if (!item_clone)
     return 0;

sql/table.cc

@@ -8057,8 +8057,12 @@ Item* TABLE_LIST::build_pushable_cond_for_table(THD *thd, Item *cond)
     {
       if (!(item->used_tables() == tab_map))
 	continue;
-      Item_func_eq *eq= 
-	new (thd->mem_root) Item_func_eq(thd, item, left_item);
+      Item_func_eq *eq= 0;
+      Item *left_item_clone= left_item->build_clone(thd, thd->mem_root);
+      Item *right_item_clone= item->build_clone(thd, thd->mem_root);
+      if (left_item_clone && right_item_clone)
+	eq= new (thd->mem_root) Item_func_eq(thd, right_item_clone,
+                                         left_item_clone);
       if (eq)
       {
 	i++;
@@ -8071,10 +8075,13 @@ Item* TABLE_LIST::build_pushable_cond_for_table(THD *thd, Item *cond)
 	  new_cond= new (thd->mem_root) Item_cond_and(thd, new_cond, eq);
 	  break;
 	default:
-	  ((Item_cond_and*)new_cond)->argument_list()->push_back(eq, thd->mem_root);
+	  ((Item_cond_and*)new_cond)->argument_list()->push_back(eq,
+                                                                 thd->mem_root);
 	}
       }
     }
+    if (new_cond)
+      new_cond->fix_fields(thd, &new_cond);
     return new_cond;
   }
   else if (cond->get_extraction_flag() != NO_EXTRACTION_FL)