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ChangeSet
1.2027 06/01/12 10:48:27 sergefp@stripped +3 -0
BUG#16166, "Can't use index_merge with FORCE INDEX": adjust the heurstics check to take into
account that "FORCE INDEX" disables full table scans, and not range/index_merge scans.
(with post-review fixes)
sql/sql_select.cc
1.381 06/01/12 10:48:14 sergefp@stripped +28 -7
BUG#16166: "Can't use index_merge with FORCE INDEX": adjust the heuristics check:
if (force-index-is-used && there-is-possible-ref-access &&
+ THERE IS NO POSSIBLE RANGE/INDEX_MERGE ACCESS)
{
...
mysql-test/t/index_merge.test
1.13 06/01/12 10:48:13 sergefp@stripped +30 -0
Testcase for BUG#16166
mysql-test/r/index_merge.result
1.18 06/01/12 10:48:13 sergefp@stripped +18 -0
Testcase for BUG#16166
# 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: sergefp
# Host: newbox.mylan
# Root: /home/psergey/mysql-5.0-bug16166-r2
--- 1.380/sql/sql_select.cc 2006-01-10 08:44:32 +03:00
+++ 1.381/sql/sql_select.cc 2006-01-12 10:48:14 +03:00
@@ -3471,13 +3471,32 @@
parts of the row from any of the used index.
This is because table scans uses index and we would not win
anything by using a table scan.
+
+ A word for word translation of the below if-statement in psergey's
+ understanding: we check if we should use table scan if:
+ (1) The found 'ref' access produces more records than a table scan
+ (or index scan, or quick select), or 'ref' is more expensive than
+ any of them.
+ (2) This doesn't hold: the best way to perform table scan is to to perform
+ 'range' access using index IDX, and the best way to perform 'ref'
+ access is to use the same index IDX, with the same or more key parts.
+ (note: it is not clear how this rule is/should be extended to
+ index_merge quick selects)
+ (3) See above note about InnoDB.
+ (4) NOT ("FORCE INDEX(...)" is used for table and there is 'ref' access
+ path, but there is no quick select)
+ If the condition in the above brackets holds, then the only possible
+ "table scan" access method is ALL/index (there is no quick select).
+ Since we have a 'ref' access path, and FORCE INDEX instructs us to
+ choose it over ALL/index, there is no need to consider a full table
+ scan.
*/
- if ((records >= s->found_records || best > s->read_time) &&
- !(s->quick && best_key && s->quick->index == best_key->key &&
- best_max_key_part >= s->table->quick_key_parts[best_key->key]) &&
- !((s->table->file->table_flags() & HA_TABLE_SCAN_ON_INDEX) &&
- ! s->table->used_keys.is_clear_all() && best_key) &&
- !(s->table->force_index && best_key))
+ if ((records >= s->found_records || best > s->read_time) && // (1)
+ !(s->quick && best_key && s->quick->index == best_key->key && // (2)
+ best_max_key_part >= s->table->quick_key_parts[best_key->key]) &&// (2)
+ !((s->table->file->table_flags() & HA_TABLE_SCAN_ON_INDEX) && // (3)
+ ! s->table->used_keys.is_clear_all() && best_key) && // (3)
+ !(s->table->force_index && best_key && !s->quick)) // (4)
{ // Check full join
ha_rows rnd_records= s->found_records;
/*
@@ -4460,13 +4479,15 @@
parts of the row from any of the used index.
This is because table scans uses index and we would not win
anything by using a table scan.
+ (see comment in best_access_path() for more details on the below
+ condition)
*/
if ((records >= s->found_records || best > s->read_time) &&
!(s->quick && best_key && s->quick->index == best_key->key &&
best_max_key_part >= s->table->quick_key_parts[best_key->key]) &&
!((s->table->file->table_flags() & HA_TABLE_SCAN_ON_INDEX) &&
! s->table->used_keys.is_clear_all() && best_key) &&
- !(s->table->force_index && best_key))
+ !(s->table->force_index && best_key & !s->quick))
{ // Check full join
ha_rows rnd_records= s->found_records;
/*
--- 1.17/mysql-test/r/index_merge.result 2005-10-17 19:08:49 +04:00
+++ 1.18/mysql-test/r/index_merge.result 2006-01-12 10:48:13 +03:00
@@ -384,3 +384,21 @@
8186
set join_buffer_size= @save_join_buffer_size;
drop table t0, t1, t2, t3, t4;
+CREATE TABLE t1 (
+cola char(3) not null, colb char(3) not null, filler char(200),
+key(cola), key(colb)
+);
+INSERT INTO t1 VALUES ('foo','bar', 'ZZ'),('fuz','baz', 'ZZ');
+OPTIMIZE TABLE t1;
+Table Op Msg_type Msg_text
+test.t1 optimize status OK
+select count(*) from t1;
+count(*)
+8704
+explain select * from t1 WHERE cola = 'foo' AND colb = 'bar';
+id select_type table type possible_keys key key_len ref rows Extra
+1 SIMPLE t1 index_merge cola,colb cola,colb 3,3 NULL 24 Using intersect(cola,colb); Using where
+explain select * from t1 force index(cola,colb) WHERE cola = 'foo' AND colb = 'bar';
+id select_type table type possible_keys key key_len ref rows Extra
+1 SIMPLE t1 index_merge cola,colb cola,colb 3,3 NULL 24 Using intersect(cola,colb); Using where
+drop table t1;
--- 1.12/mysql-test/t/index_merge.test 2005-10-17 19:08:53 +04:00
+++ 1.13/mysql-test/t/index_merge.test 2006-01-12 10:48:13 +03:00
@@ -327,3 +327,33 @@
drop table t0, t1, t2, t3, t4;
+# BUG#16166
+CREATE TABLE t1 (
+ cola char(3) not null, colb char(3) not null, filler char(200),
+ key(cola), key(colb)
+);
+INSERT INTO t1 VALUES ('foo','bar', 'ZZ'),('fuz','baz', 'ZZ');
+
+--disable_query_log
+let $1=9;
+while ($1)
+{
+ eval INSERT INTO t1 SELECT * from t1 WHERE cola = 'foo';
+ dec $1;
+}
+
+let $1=13;
+while ($1)
+{
+ eval INSERT INTO t1 SELECT * from t1 WHERE cola <> 'foo';
+ dec $1;
+}
+
+--enable_query_log
+
+OPTIMIZE TABLE t1;
+select count(*) from t1;
+explain select * from t1 WHERE cola = 'foo' AND colb = 'bar';
+explain select * from t1 force index(cola,colb) WHERE cola = 'foo' AND colb = 'bar';
+drop table t1;
+
| Thread |
|---|
| • bk commit into 5.0 tree (sergefp:1.2027) BUG#16166 | Sergey Petrunia | 12 Jan |
