Fixed LP bug #803851.

The function generate_derived_keys_for_table should set the value of
the number of keys for the derived table to 0 before it starts 
generating key definitions for the table. It's important as the
function can be called twice by the optimizer for a derived table
if the query contains a subquery to which the IN-EXIST transformation
is applicable.

Fixed a valgrind complain.

mysql-test/r/derived_view.result

@@ -735,3 +735,33 @@ INSERT INTO t1 VALUES (7), (1), (3);
 SELECT * FROM (SELECT * FROM t1 LIMIT 0) t;
 a
 DROP TABLE t1;
+#
+# LP bug #803851: materialized view + IN->EXISTS                       
+#                 
+SET SESSION optimizer_switch='semijoin=off,derived_with_keys=on';
+CREATE TABLE t1 (a int, b int);
+INSERT INTO t1 VALUES (2,2), (3,3), (1,1);
+CREATE TABLE t2 (a int);
+INSERT INTO t2 VALUES (1), (2), (1);
+CREATE TABLE t3 (a int);
+INSERT INTO t3 VALUES (3), (1), (2), (1);
+CREATE VIEW v1 AS SELECT a, MAX(b) AS b FROM t1 GROUP BY a;
+EXPLAIN EXTENDED
+SELECT * FROM t3
+WHERE t3.a IN (SELECT v1.a FROM v1, t2 WHERE t2.a = v1.b);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	4	100.00	Using where
+2	DEPENDENT SUBQUERY	<derived3>	ref	key0	key0	5	func	2	100.00	
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where; Using join buffer (flat, BNL join)
+3	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using temporary; Using filesort
+Warnings:
+Note	1003	select `test`.`t3`.`a` AS `a` from `test`.`t3` where <expr_cache><`test`.`t3`.`a`>(<in_optimizer>(`test`.`t3`.`a`,<exists>(select `v1`.`a` from `test`.`v1` join `test`.`t2` where ((`test`.`t2`.`a` = `v1`.`b`) and (<cache>(`test`.`t3`.`a`) = `v1`.`a`)))))
+SELECT * FROM t3
+WHERE t3.a IN (SELECT v1.a FROM v1, t2 WHERE t2.a = v1.b);
+a
+1
+2
+1
+SET SESSION optimizer_switch=default;
+DROP VIEW v1;
+DROP TABLE t1,t2,t3;

mysql-test/t/derived_view.test

@@ -358,4 +358,30 @@ SELECT * FROM (SELECT * FROM t1 LIMIT 0) t;
 
 DROP TABLE t1;
 
+--echo #
+--echo # LP bug #803851: materialized view + IN->EXISTS                       
+--echo #                 
+
+SET SESSION optimizer_switch='semijoin=off,derived_with_keys=on';
+
+CREATE TABLE t1 (a int, b int);
+INSERT INTO t1 VALUES (2,2), (3,3), (1,1);
+
+CREATE TABLE t2 (a int);
+INSERT INTO t2 VALUES (1), (2), (1);
+
+CREATE TABLE t3 (a int);
+INSERT INTO t3 VALUES (3), (1), (2), (1);
 
+CREATE VIEW v1 AS SELECT a, MAX(b) AS b FROM t1 GROUP BY a;
+
+EXPLAIN EXTENDED
+SELECT * FROM t3
+  WHERE t3.a IN (SELECT v1.a FROM v1, t2 WHERE t2.a = v1.b);
+SELECT * FROM t3
+  WHERE t3.a IN (SELECT v1.a FROM v1, t2 WHERE t2.a = v1.b);
+
+SET SESSION optimizer_switch=default;
+
+DROP VIEW v1;
+DROP TABLE t1,t2,t3;

sql/table.cc

@@ -5232,8 +5232,8 @@ void st_table::mark_virtual_columns_for_write(bool insert_fl)
 
 bool TABLE::alloc_keys(uint key_count)
 {
-  DBUG_ASSERT(!s->keys);
   key_info= s->key_info= (KEY*) alloc_root(&mem_root, sizeof(KEY)*key_count);
+  s->keys= 0;
   max_keys= key_count;
   return !(key_info);
 }
@@ -5374,7 +5374,7 @@ void TABLE::use_index(int key_to_save)
   DBUG_ASSERT(!created && key_to_save < (int)s->keys);
   if (key_to_save >= 0)
     /* Save the given key. */
-    memcpy(key_info, key_info + key_to_save, sizeof(KEY));
+    memmove(key_info, key_info + key_to_save, sizeof(KEY));
   else
     /* Drop all keys; */
     i= 0;