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

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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.
This commit is contained in:
ingo@mysql.com
2004-05-06 15:53:01 +02:00
parent 4d8235b849
commit 784c9526ec
12 changed files with 530 additions and 62 deletions
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4
sql/sql_select.cc
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@ -1,4 +1,4 @@
/* Copyright (C) 2000-2003 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
@ -5545,6 +5545,8 @@ bool create_myisam_from_heap(THD *thd, TABLE *table, TMP_TABLE_PARAM *param,
goto err2;
if (open_tmp_table(&new_table))
goto err1;
if (table->file->indexes_are_disabled())
new_table.file->disable_indexes(HA_KEY_SWITCH_ALL);
table->file->index_end();
table->file->rnd_init();
if (table->no_rows)