BUG#20256 - LOCK WRITE - MyISAM

Only MyISAM tables locked with LOCK TABLES ... WRITE were affected.

A query that is optimized with index_merge doesn't reflect rows
inserted within LOCK TABLES.

MyISAM doesn't flush a state within LOCK TABLES. index_merge
optimization creates a copy of the handler, which thus gets
outdated MyISAM state.

New handler->clone() method is introduced to fix this problem.
For non-MyISAM storage engines it allocates a handler and opens
it with ha_open(). For MyISAM it additionally copies MyISAM state
pointer to cloned handler.

mysql-test/r/index_merge.result

@@ -424,3 +424,34 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t3	index_merge	a,b	a,b	5,5	NULL	#	Using intersect(a,b); Using where
 drop table t3;
 drop table t0, t1, t2;
+CREATE TABLE t1(a INT);
+INSERT INTO t1 VALUES(1);
+CREATE TABLE t2(a INT, b INT, dummy CHAR(16) DEFAULT '', KEY(a), KEY(b));
+INSERT INTO t2(a,b) VALUES
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(1,2);
+LOCK TABLES t1 WRITE, t2 WRITE;
+INSERT INTO t2(a,b) VALUES(1,2);
+SELECT t2.a FROM t1,t2 WHERE t2.b=2 AND t2.a=1;
+a
+1
+1
+UNLOCK TABLES;
+DROP TABLE t1, t2;

mysql-test/t/index_merge.test

@@ -383,3 +383,35 @@ explain select * from t3 where a=1 and b=1;
 
 drop table t3;
 drop table t0, t1, t2;
+
+#
+# BUG#20256 - LOCK WRITE - MyISAM
+#
+CREATE TABLE t1(a INT);
+INSERT INTO t1 VALUES(1);
+CREATE TABLE t2(a INT, b INT, dummy CHAR(16) DEFAULT '', KEY(a), KEY(b));
+INSERT INTO t2(a,b) VALUES
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
+(1,2);
+LOCK TABLES t1 WRITE, t2 WRITE;
+INSERT INTO t2(a,b) VALUES(1,2);
+SELECT t2.a FROM t1,t2 WHERE t2.b=2 AND t2.a=1;
+UNLOCK TABLES;
+DROP TABLE t1, t2;

sql/ha_myisam.cc

@@ -169,6 +169,14 @@ ha_myisam::ha_myisam(TABLE *table_arg)
   can_enable_indexes(1)
 {}
 
+handler *ha_myisam::clone(MEM_ROOT *mem_root)
+{
+  ha_myisam *new_handler= static_cast <ha_myisam *>(handler::clone(mem_root));
+  if (new_handler)
+    new_handler->file->state= file->state;
+  return new_handler;
+}
+
 
 static const char *ha_myisam_exts[] = {
   ".MYI",

sql/ha_myisam.h

@@ -45,6 +45,7 @@ class ha_myisam: public handler
  public:
   ha_myisam(TABLE *table_arg);
   ~ha_myisam() {}
+  handler *clone(MEM_ROOT *mem_root);
   const char *table_type() const { return "MyISAM"; }
   const char *index_type(uint key_number);
   const char **bas_ext() const;

sql/handler.cc

@@ -1372,6 +1372,15 @@ int ha_delete_table(THD *thd, enum db_type table_type, const char *path,
 /****************************************************************************
 ** General handler functions
 ****************************************************************************/
+handler *handler::clone(MEM_ROOT *mem_root)
+{
+  handler *new_handler= get_new_handler(table, mem_root, table->s->db_type);
+  if (new_handler && !new_handler->ha_open(table->s->path, table->db_stat,
+                                           HA_OPEN_IGNORE_IF_LOCKED))
+    return new_handler;
+  return NULL;
+}
+
 
 	/* Open database-handler. Try O_RDONLY if can't open as O_RDWR */
 	/* Don't wait for locks if not HA_OPEN_WAIT_IF_LOCKED is set */

sql/handler.h

@@ -563,6 +563,7 @@ class handler :public Sql_alloc
     pushed_cond(NULL)
     {}
   virtual ~handler(void) { /* TODO: DBUG_ASSERT(inited == NONE); */ }
+  virtual handler *clone(MEM_ROOT *mem_root);
   int ha_open(const char *name, int mode, int test_if_locked);
   void adjust_next_insert_id_after_explicit_value(ulonglong nr);
   bool update_auto_increment();

sql/opt_range.cc

@@ -1033,10 +1033,7 @@ int QUICK_RANGE_SELECT::init_ror_merged_scan(bool reuse_handler)
   }
 
   THD *thd= current_thd;
-  if (!(file= get_new_handler(head, thd->mem_root, head->s->db_type)))
-    goto failure;
-  DBUG_PRINT("info", ("Allocated new handler %p", file));
-  if (file->ha_open(head->s->path, head->db_stat, HA_OPEN_IGNORE_IF_LOCKED))
+  if (!(file= head->file->clone(thd->mem_root)))
   {
     /* Caller will free the memory */
     goto failure;