BUG#21617 - crash when selecting from merge table with inconsistent indexes

Crash may happen when selecting from a merge table that has underlying
tables with less indexes than in a merge table itself.

If number of keys in merge table is not bigger than requested key number,
return error.

myisammrg/myrg_open.c

@@ -33,7 +33,7 @@
 MYRG_INFO *myrg_open(const char *name, int mode, int handle_locking)
 {
   int save_errno,errpos=0;
-  uint files=0,i,dir_length,length,key_parts;
+  uint files= 0, i, dir_length, length, key_parts, min_keys= 0;
   ulonglong file_offset=0;
   char name_buff[FN_REFLEN*2],buff[FN_REFLEN],*end;
   MYRG_INFO *m_info=0;
@@ -106,6 +106,7 @@ MYRG_INFO *myrg_open(const char *name, int mode, int handle_locking)
         files= 0;
       }
       m_info->reclength=isam->s->base.reclength;
+      min_keys= isam->s->base.keys;
       errpos=3;
     }
     m_info->open_tables[files].table= isam;
@@ -121,6 +122,8 @@ MYRG_INFO *myrg_open(const char *name, int mode, int handle_locking)
     m_info->records+= isam->state->records;
     m_info->del+= isam->state->del;
     m_info->data_file_length+= isam->state->data_file_length;
+    if (min_keys > isam->s->base.keys)
+      min_keys= isam->s->base.keys;
     for (i=0; i < key_parts; i++)
       m_info->rec_per_key_part[i]+= (isam->s->state.rec_per_key_part[i] /
                                      m_info->tables);
@@ -138,7 +141,7 @@ MYRG_INFO *myrg_open(const char *name, int mode, int handle_locking)
     my_errno=HA_ERR_RECORD_FILE_FULL;
     goto err;
   }
-  m_info->keys= files ? isam->s->base.keys : 0;
+  m_info->keys= min_keys;
   bzero((char*) &m_info->by_key,sizeof(m_info->by_key));
 
   /* this works ok if the table list is empty */

myisammrg/myrg_queue.c

@@ -51,6 +51,8 @@ int _myrg_init_queue(MYRG_INFO *info,int inx,enum ha_rkey_function search_flag)
 	error=my_errno;
     }
   }
+  else
+    my_errno= error= HA_ERR_WRONG_INDEX;
   return error;
 }
 

mysql-test/r/merge.result

@@ -766,3 +766,9 @@ Table	Op	Msg_type	Msg_text
 test.t1	check	status	OK
 test.t2	check	status	OK
 drop table t1, t2, t3;
+CREATE TABLE t1(a INT);
+INSERT INTO t1 VALUES(2),(1);
+CREATE TABLE t2(a INT, KEY(a)) ENGINE=MERGE UNION=(t1);
+SELECT * FROM t2 WHERE a=2;
+ERROR HY000: Got error 124 from storage engine
+DROP TABLE t1, t2;

mysql-test/t/merge.test

@@ -376,4 +376,15 @@ select * from t3;
 check table t1, t2;
 drop table t1, t2, t3;
 
+#
+# BUG#21617 - crash when selecting from merge table with inconsistent
+# indexes
+#
+CREATE TABLE t1(a INT);
+INSERT INTO t1 VALUES(2),(1);
+CREATE TABLE t2(a INT, KEY(a)) ENGINE=MERGE UNION=(t1);
+--error 1030
+SELECT * FROM t2 WHERE a=2;
+DROP TABLE t1, t2;
+
 # End of 4.1 tests

mysys/queues.c

@@ -164,28 +164,22 @@ void delete_queue(QUEUE *queue)
 
 void queue_insert(register QUEUE *queue, byte *element)
 {
-  reg2 uint idx,next;
+  reg2 uint idx, next;
   int cmp;
-
-#ifndef DBUG_OFF
-  if (queue->elements < queue->max_elements)
-#endif
-  {
-    queue->root[0]=element;
+  DBUG_ASSERT(queue->elements < queue->max_elements);
+  queue->root[0]= element;
   idx= ++queue->elements;
-
   /* max_at_top swaps the comparison if we want to order by desc */
-    while ((cmp=queue->compare(queue->first_cmp_arg,
-			       element+queue->offset_to_key,
-			       queue->root[(next=idx >> 1)] +
+  while ((cmp= queue->compare(queue->first_cmp_arg,
+                              element + queue->offset_to_key,
+                              queue->root[(next= idx >> 1)] +
                               queue->offset_to_key)) &&
          (cmp ^ queue->max_at_top) < 0)
   {
-      queue->root[idx]=queue->root[next];
-      idx=next;
-    }
-    queue->root[idx]=element;
+    queue->root[idx]= queue->root[next];
+    idx= next;
   }
+  queue->root[idx]= element;
 }
 
 	/* Remove item from queue */
@@ -193,16 +187,12 @@ void queue_insert(register QUEUE *queue, byte *element)
 
 byte *queue_remove(register QUEUE *queue, uint idx)
 {
-#ifndef DBUG_OFF
-  if (idx >= queue->max_elements)
-    return 0;
-#endif
-  {
-    byte *element=queue->root[++idx];	/* Intern index starts from 1 */
-    queue->root[idx]=queue->root[queue->elements--];
-    _downheap(queue,idx);
+  byte *element;
+  DBUG_ASSERT(idx < queue->max_elements);
+  element= queue->root[++idx];  /* Intern index starts from 1 */
+  queue->root[idx]= queue->root[queue->elements--];
+  _downheap(queue, idx);
   return element;
-  }
 }
 
 	/* Fix when element on top has been replaced */