Proposed bugfix for #712

Monty revoked any locks for temporary tables in
ha_myisam::external_lock()
But further code bans using write cache on nonlocked tables
this makes operations much slower


myisam/mi_locking.c:
  Handling of MI_TEMPORARY_TABLE lock
myisam/myisamdef.h:
  defining of MI_TEMPORARY_TABLE
sql/ha_myisam.cc:
  now we lock temporary tables using MI_TEMPORARY_TABLE lock

myisam/mi_locking.c

@@ -39,6 +39,14 @@ int mi_lock_database(MI_INFO *info, int lock_type)
   if (share->options & HA_OPTION_READ_ONLY_DATA ||
       info->lock_type == lock_type)
     DBUG_RETURN(0);
+  if (lock_type == MI_TEMPORARY_TABLE)
+  {
+    ++share->w_locks;
+    ++share->tot_locks;
+    info->lock_type= lock_type;
+    DBUG_RETURN(0);
+  }
+
   flag=error=0;
   pthread_mutex_lock(&share->intern_lock);
   if (share->kfile >= 0)		/* May only be false on windows */

myisam/myisamdef.h

@@ -101,6 +101,7 @@ typedef struct st_mi_state_info
 #define MI_COLUMNDEF_SIZE	(2*3+1)
 #define MI_BASE_INFO_SIZE	(5*8 + 8*4 + 4 + 4*2 + 16)
 #define MI_INDEX_BLOCK_MARGIN	16	/* Safety margin for .MYI tables */
+#define MI_TEMPORARY_TABLE      ((1 & ~F_RDLCK) | (2 & ~F_WRLCK) | (4 & ~F_UNLCK))
 
 typedef struct st_mi_base_info
 {

sql/ha_myisam.cc

@@ -559,7 +559,8 @@ int ha_myisam::repair(THD *thd, MI_CHECK &param, bool optimize)
   strmov(fixed_name,file->filename);
 
   // Don't lock tables if we have used LOCK TABLE
-  if (!thd->locked_tables && mi_lock_database(file,F_WRLCK))
+  if (!thd->locked_tables && 
+      mi_lock_database(file, table->tmp_table ? MI_TEMPORARY_TABLE : F_WRLCK))
   {
     mi_check_print_error(&param,ER(ER_CANT_LOCK),my_errno);
     DBUG_RETURN(HA_ADMIN_FAILED);
@@ -999,9 +1000,9 @@ int ha_myisam::delete_table(const char *name)
 
 int ha_myisam::external_lock(THD *thd, int lock_type)
 {
-  if (!table->tmp_table)
-    return mi_lock_database(file,lock_type);
-  return 0;
+  return mi_lock_database(file, !table->tmp_table ?
+			  lock_type : ((lock_type == F_UNLCK) ?
+				       F_UNLCK : MI_TEMPORARY_TABLE));
 }