WL#1687 - Optimize UNION DISTINCT ... UNION ALL (again).

HEAP: Copies the key count to a backup variable and sets the key count to zero.
That way, no HEAP function will ever try to touch any index.
Re-enabling is done by copying back the backup variable.
To avoid memory leak at table close, disable deletes all index trees.
Re-enabling must be done with empty indexes and data anyway. Otherwise,
the indexes would need to be repaired, wich HEAP is not capable of.
MyISAM: Only the key_map is cleared and set.
Re-enabling must be done with empty indexes and data. Otherwise, repair needs
to be done which will enable all keys persistently.
The former implementation disabled only non-unique keys and maked this persistent.
The new implementation additionally can disable all keys, but only without
making this persistent. Re-enabling all keys can be done without repair,
if data file and indexes are empty.

1 files changed, 4 insertions, 1 deletions

diff --git a/myisam/myisamdef.h b/myisam/myisamdef.h
index 0f43fe7fb61..1f100590049 100644
--- a/myisam/myisamdef.h
+++ b/myisam/myisamdef.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB
+/* Copyright (C) 2000,2004 MySQL AB & MySQL Finland AB & TCX DataKonsult AB
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -684,6 +684,9 @@ uint mi_uniquedef_write(File file, MI_UNIQUEDEF *keydef);
 char *mi_uniquedef_read(char *ptr, MI_UNIQUEDEF *keydef);
 uint mi_recinfo_write(File file, MI_COLUMNDEF *recinfo);
 char *mi_recinfo_read(char *ptr, MI_COLUMNDEF *recinfo);
+extern int mi_disable_indexes(MI_INFO *info);
+extern int mi_enable_indexes(MI_INFO *info);
+extern int mi_indexes_are_disabled(MI_INFO *info);
 ulong _my_calc_total_blob_length(MI_INFO *info, const byte *record);
 ha_checksum mi_checksum(MI_INFO *info, const byte *buf);
 ha_checksum mi_static_checksum(MI_INFO *info, const byte *buf);