Fix for bug #35392: Delete all statement does not execute properly

after few delete statements

Problem: changing a file size might require that it must be 
unmapped beforehand.
  
Fix: unmap the file before changing its size.


mysql-test/r/temp_table.result:
  Fix for bug #35392: Delete all statement does not execute properly 
  after few delete statements
    - test result.
mysql-test/t/temp_table.test:
  Fix for bug #35392: Delete all statement does not execute properly 
  after few delete statements
    - test case.
storage/myisam/mi_delete_all.c:
  Fix for bug #35392: Delete all statement does not execute properly 
  after few delete statements
    - unmap file before changing its size as it's required 
      by SetEndOfFile() function (see my_chsize()).
    - as no other threads allowed to perform concurrent inserts 
      when delete_all is called, mmap_lock locking removed.

mysql-test/r/temp_table.result

@@ -184,3 +184,14 @@ select * from t1;
 a
 42
 drop table t1;
+CREATE TEMPORARY TABLE t1(a INT, b VARCHAR(20));
+INSERT INTO t1 VALUES(1, 'val1'), (2, 'val2'), (3, 'val3');
+DELETE FROM t1 WHERE a=1;
+SELECT count(*) FROM t1;
+count(*)
+2
+DELETE FROM t1;
+SELECT * FROM t1;
+a	b
+DROP TABLE t1;
+End of 5.1 tests

mysql-test/t/temp_table.test

@@ -191,3 +191,17 @@ truncate t1;
 insert into t1 values (42);
 select * from t1;
 drop table t1;
+
+#
+# Bug #35392: Delete all statement does not execute properly after 
+# few delete statements
+#
+CREATE TEMPORARY TABLE t1(a INT, b VARCHAR(20));
+INSERT INTO t1 VALUES(1, 'val1'), (2, 'val2'), (3, 'val3');
+DELETE FROM t1 WHERE a=1;
+SELECT count(*) FROM t1;
+DELETE FROM t1;
+SELECT * FROM t1;
+DROP TABLE t1;
+
+--echo End of 5.1 tests

storage/myisam/mi_delete_all.c

@@ -53,15 +53,18 @@ int mi_delete_all_rows(MI_INFO *info)
     since it was locked then there may be key blocks in the key cache
   */
   flush_key_blocks(share->key_cache, share->kfile, FLUSH_IGNORE_CHANGED);
+#ifdef HAVE_MMAP
+  if (share->file_map)
+    _mi_unmap_file(info);
+#endif
   if (my_chsize(info->dfile, 0, 0, MYF(MY_WME)) ||
       my_chsize(share->kfile, share->base.keystart, 0, MYF(MY_WME))  )
     goto err;
   VOID(_mi_writeinfo(info,WRITEINFO_UPDATE_KEYFILE));
 #ifdef HAVE_MMAP
-  /* Resize mmaped area */
-  rw_wrlock(&info->s->mmap_lock);
-  mi_remap_file(info, (my_off_t)0);
-  rw_unlock(&info->s->mmap_lock);
+  /* Map again */
+  if (share->file_map)
+    mi_dynmap_file(info, (my_off_t) 0);
 #endif
   allow_break();			/* Allow SIGHUP & SIGINT */
   DBUG_RETURN(0);