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.


heap/heapdef.h:
  WL#1687 - Optimize UNION DISTINCT ... UNION ALL (again).
  Pulled hp_clear_keys() out of hp_clear().
heap/hp_clear.c:
  WL#1687 - Optimize UNION DISTINCT ... UNION ALL (again).
  Pulled hp_clear_keys() out of hp_clear().
  Added the new functions for disabling and enabling keys and to ask for the key state.
include/heap.h:
  WL#1687 - Optimize UNION DISTINCT ... UNION ALL (again).
  Added a new HP_SHARE element to save the key count while keys are disabled.
  Added declarations for the new functions.
myisam/mi_open.c:
  WL#1687 - Optimize UNION DISTINCT ... UNION ALL (again).
  Added the new functions for disabling and enabling keys and to ask for the key state.
myisam/myisamdef.h:
  WL#1687 - Optimize UNION DISTINCT ... UNION ALL (again).
  Added declarations for the new functions.
sql/ha_heap.cc:
  WL#1687 - Optimize UNION DISTINCT ... UNION ALL (again).
  Pulled set_keys_for_scanning() out of open().
  Added the new functions for disabling and enabling keys and to ask for the key state.
sql/ha_heap.h:
  WL#1687 - Optimize UNION DISTINCT ... UNION ALL (again).
  Added declarations for the new functions.
sql/ha_myisam.cc:
  WL#1687 - Optimize UNION DISTINCT ... UNION ALL (again).
  Extended disable_indexes() for all keys and no save.
  The argument is now 'mode' as it must handle different cases.
  Extended enable_indexes() for no save.
  The new feature needs the new argument 'mode' with the same semantics as in disable_indexes().
  Added indexes_are_disabled() to ask for the key state.
  Extended the existing call to enable_indexes() by the new argument.
sql/ha_myisam.h:
  WL#1687 - Optimize UNION DISTINCT ... UNION ALL (again).
  Modified the declarations of dis-/enable_indexes() for the new argument.
  Added the declaration of the new function to ask for the key state.
sql/handler.h:
  WL#1687 - Optimize UNION DISTINCT ... UNION ALL (again).
  Added declarations for the operation modes for the key switching functions.
  Modified the declarations of dis-/enable_indexes() for the new argument.
  Added the declaration of the new function to ask for the key state.
sql/sql_select.cc:
  WL#1687 - Optimize UNION DISTINCT ... UNION ALL (again).
  In create_myisam_from_heap() take notice of disabled keys
  and disable them in the new table before copying the data.
sql/sql_table.cc:
  WL#1687 - Optimize UNION DISTINCT ... UNION ALL (again).
  Modified the calls of dis-/enable_indexes() for the new argument.

1 files changed, 6 insertions, 1 deletions

diff --git a/include/heap.h b/include/heap.h
index c5f2be81fb7..b536937c8c0 100644
--- a/include/heap.h
+++ b/include/heap.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2000 MySQL AB
+/* Copyright (C) 2000,2004 MySQL 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
@@ -107,6 +107,7 @@ typedef struct st_heap_share
   uint reclength;			/* Length of one record */
   uint changed;
   uint keys,max_key_length;
+  uint currently_disabled_keys;    /* saved value from "keys" when disabled */
   uint open_count;
   byte *del_link;			/* Link to next block with del. rec */
   my_string name;			/* Name of "memory-file" */
@@ -176,6 +177,10 @@ extern int heap_rprev(HP_INFO *info,byte *record);
 extern int heap_rfirst(HP_INFO *info,byte *record,int inx);
 extern int heap_rlast(HP_INFO *info,byte *record,int inx);
 extern void heap_clear(HP_INFO *info);
+extern void heap_clear_keys(HP_INFO *info);
+extern int heap_disable_indexes(HP_INFO *info);
+extern int heap_enable_indexes(HP_INFO *info);
+extern int heap_indexes_are_disabled(HP_INFO *info);
 extern void heap_update_auto_increment(HP_INFO *info, const byte *record);
 ha_rows hp_rb_records_in_range(HP_INFO *info, int inx, const byte *start_key,
 			       uint start_key_len,