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, 82 insertions, 1 deletions

diff --git a/myisam/mi_open.c b/myisam/mi_open.c
index 2c4661c4d3e..53cf87b24b4 100644
--- a/myisam/mi_open.c
+++ b/myisam/mi_open.c
@@ -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
@@ -1151,3 +1151,84 @@ int mi_open_keyfile(MYISAM_SHARE *share)
     return 1;
   return 0;
 }
+
+
+/*
+  Disable all indexes.
+
+  SYNOPSIS
+    mi_disable_indexes()
+    info        A pointer to the MyISAM storage engine MI_INFO struct.
+
+  DESCRIPTION
+    Disable all indexes.
+
+  RETURN
+    0  ok
+*/
+
+int mi_disable_indexes(MI_INFO *info)
+{
+  MYISAM_SHARE *share= info->s;
+
+  share->state.key_map= 0;
+  return 0;
+}
+
+
+/*
+  Enable all indexes
+
+  SYNOPSIS
+    mi_enable_indexes()
+    info        A pointer to the MyISAM storage engine MI_INFO struct.
+
+  DESCRIPTION
+    Enable all indexes. The indexes might have been disabled
+    by mi_disable_index() before.
+    The function works only if both data and indexes are empty,
+    otherwise a repair is required.
+    To be sure, call handler::delete_all_rows() before.
+
+  RETURN
+    0  ok
+    HA_ERR_CRASHED data or index is non-empty.
+*/
+
+int mi_enable_indexes(MI_INFO *info)
+{
+  int error= 0;
+  MYISAM_SHARE *share= info->s;
+
+  if (share->state.state.data_file_length ||
+      (share->state.state.key_file_length != share->base.keystart))
+    error= HA_ERR_CRASHED;
+  else
+    share->state.key_map= ((ulonglong) 1L << share->base.keys) - 1;
+  return error;
+}
+
+
+/*
+  Test if indexes are disabled.
+
+  SYNOPSIS
+    mi_indexes_are_disabled()
+    info        A pointer to the MyISAM storage engine MI_INFO struct.
+
+  DESCRIPTION
+    Test if indexes are disabled.
+
+  RETURN
+    0  indexes are not disabled
+    1  all indexes are disabled
+   [2  non-unique indexes are disabled - NOT YET IMPLEMENTED]
+*/
+
+int mi_indexes_are_disabled(MI_INFO *info)
+{
+  MYISAM_SHARE *share= info->s;
+
+  return (! share->state.key_map && share->base.keys);
+}
+