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ChangeSet@stripped, 2007-01-26 12:36:29+01:00, mhansson@stripped +5 -0
BUG#20604: FORCE INDEX uses keys disabled by ALTER TABLE
The function that checks whether we can use keys for aggregates,
find_key_for_maxmin(), assumes that keys disabled by ALTER TABLE
... DISABLE KEYS are not in the set table->keys_in_use_for_query.
I.E., if a key is in this set, the optimizer assumes it is free to
use it.
The bug is that keys disabled with ALTER TABLE ... DISABLE KEYS still
appear in table->keys_in_use_for_query When the TABLE object has been
initialized with setup_tables(). Before setup_tables is called, however,
keys that are disabled in the aforementioned way are not included in
TABLE::keys_in_use_for_query.
The provided patch changes the code that updates keys_is_use_for_query so
that it assumes that keys_is_use_for_query already takes into account all
disabled keys, and generally all keys that should be used by the query.
mysql-test/r/key.result@stripped, 2007-01-26 12:36:22+01:00, mhansson@stripped +7 -0
Test for BUG#20604.
The important part of the test is the explain output that
tests what indexes are used.
mysql-test/t/key.test@stripped, 2007-01-26 12:36:23+01:00, mhansson@stripped +11 -0
The minimal test case that reveals the bug. The optimizer for
aggregates relies on keys disabled with ALTER TABLE ... DISABLE KEYS
not being in the set TABLE::keys_in_use_for_query.
When the execution engine tries to use a disabled index, MyISAM
returns an error.
sql/sql_base.cc@stripped, 2007-01-26 12:36:23+01:00, mhansson@stripped +6 -0
Exclude the keys disabled by ALTER TABLE ... DISABLE_KEYS
from TABLE::keys_in_use_for_query, and in general, don't
introduce any new keys. We may not know why keys have been
removed at previous stages.
sql/sql_select.cc@stripped, 2007-01-26 12:36:23+01:00, mhansson@stripped +6 -5
The intersection operation between table->s->keys_in_use and
table->keys_in_use_for_query is no longer necessary.
We can trust that the latter is a subset of the former.
sql/table.h@stripped, 2007-01-26 12:36:23+01:00, mhansson@stripped +22 -2
Added comments to TABLE_SHARE::keys_in_use and
TABLE::keys_in_use_for_query.
# This is a BitKeeper patch. What follows are the unified diffs for the
# set of deltas contained in the patch. The rest of the patch, the part
# that BitKeeper cares about, is below these diffs.
# User: mhansson
# Host: linux-st28.site
# Root: /home/martin/mysql/src/5.1o-bug20604-tp
--- 1.372/sql/sql_base.cc 2007-01-24 16:51:05 +01:00
+++ 1.373/sql/sql_base.cc 2007-01-26 12:36:23 +01:00
@@ -5462,6 +5462,12 @@ bool setup_tables(THD *thd, Name_resolut
get_key_map_from_key_list(&map, table, table_list->use_index);
if (map.is_set_all())
DBUG_RETURN(1);
+ /*
+ Don't introduce keys in keys_in_use_for_query that weren't there
+ before. FORCE/USE INDEX should not add keys, it should only remove
+ all keys except the key(s) specified in the hint.
+ */
+ map.intersect(table->keys_in_use_for_query);
table->keys_in_use_for_query=map;
}
if (table_list->ignore_index)
--- 1.485/sql/sql_select.cc 2007-01-25 00:30:31 +01:00
+++ 1.486/sql/sql_select.cc 2007-01-26 12:36:23 +01:00
@@ -12262,13 +12262,14 @@ test_if_skip_sort_order(JOIN_TAB *tab,OR
DBUG_ENTER("test_if_skip_sort_order");
LINT_INIT(ref_key_parts);
+ /* Check which keys can be used to resolve ORDER BY. */
+ usable_keys= table->keys_in_use_for_query;
+
/*
- Check which keys can be used to resolve ORDER BY.
- We must not try to use disabled keys.
+ Keys disabled by ALTER TABLE ... DISABLE KEYS should have already
+ been taken into account.
*/
- usable_keys= table->s->keys_in_use;
- /* we must not consider keys that are disabled by IGNORE INDEX */
- usable_keys.intersect(table->keys_in_use_for_query);
+ DBUG_ASSERT(usable_keys.is_subset(table->s->keys_in_use));
for (ORDER *tmp_order=order; tmp_order ; tmp_order=tmp_order->next)
{
--- 1.158/sql/table.h 2007-01-15 10:39:27 +01:00
+++ 1.159/sql/table.h 2007-01-26 12:36:23 +01:00
@@ -158,7 +158,12 @@ typedef struct st_table_share
LEX_STRING path; /* Path to .frm file (from datadir) */
LEX_STRING normalized_path; /* unpack_filename(path) */
LEX_STRING connect_string;
- key_map keys_in_use; /* Keys in use for table */
+
+ /*
+ Set of keys in use, implemented as a Bitmap.
+ Excludes keys disabled by ALTER TABLE ... DISABLE KEYS.
+ */
+ key_map keys_in_use;
key_map keys_for_keyread;
ha_rows min_rows, max_rows; /* create information */
ulong avg_row_length; /* create information */
@@ -313,7 +318,22 @@ struct st_table {
byte *write_row_record; /* Used as optimisation in
THD::write_row */
byte *insert_values; /* used by INSERT ... UPDATE */
- key_map quick_keys, used_keys, keys_in_use_for_query, merge_keys;
+
+ key_map quick_keys, used_keys;
+
+ /*
+ A set of keys that can be used in the query that references this
+ table
+
+ All indexes disabled on the table's TABLE_SHARE (see TABLE::s) will be
+ subtracted from this set upon instantiation. Thus for any TABLE t it holds
+ that t.keys_in_use_for_query is a subset of t.s.keys_in_use. Generally we
+ must not introduce any new keys here (see setup_tables).
+
+ The set is implemented as a bitmap.
+ */
+ key_map keys_in_use_for_query;
+ key_map merge_keys;
KEY *key_info; /* data of keys in database */
Field *next_number_field; /* Set if next_number is activated */
--- 1.40/mysql-test/r/key.result 2006-08-11 23:06:20 +02:00
+++ 1.41/mysql-test/r/key.result 2007-01-26 12:36:22 +01:00
@@ -482,3 +482,10 @@ alter table t1 drop index i3, drop index
alter table t1 add index i3 (c3), add index i2 (c2), add unique index i1 (c1);
ERROR 23000: Duplicate entry '1' for key 'i1'
drop table t1;
+CREATE TABLE t1( a TINYINT, KEY(a) ) ENGINE=MyISAM;
+INSERT INTO t1 VALUES( 1 );
+ALTER TABLE t1 DISABLE KEYS;
+EXPLAIN SELECT MAX(a) FROM t1 FORCE INDEX(a);
+id select_type table type possible_keys key key_len ref rows Extra
+1 SIMPLE t1 system NULL NULL NULL NULL 1
+drop table t1;
--- 1.31/mysql-test/t/key.test 2006-07-20 20:41:52 +02:00
+++ 1.32/mysql-test/t/key.test 2007-01-26 12:36:23 +01:00
@@ -442,3 +442,14 @@ alter table t1 drop index i3, drop index
alter table t1 add index i3 (c3), add index i2 (c2), add unique index i1 (c1);
drop table t1;
+
+#
+# Bug #20604: Test for disabled keys with aggregate functions and FORCE INDEX.
+#
+
+CREATE TABLE t1( a TINYINT, KEY(a) ) ENGINE=MyISAM;
+INSERT INTO t1 VALUES( 1 );
+ALTER TABLE t1 DISABLE KEYS;
+EXPLAIN SELECT MAX(a) FROM t1 FORCE INDEX(a);
+
+drop table t1;
| Thread |
|---|
| • bk commit into 5.1 tree (mhansson:1.2409) BUG#20604 | mhansson | 26 Jan |
