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fix for bug #1724 'WHERE ... IN() optimizer behaviour

Browse Source 
has changed since 4.0.14'
We need to calculate cost of RANGE
scan if it is present instead of cost of 
FULL scan.


mysql-test/r/order_by.result:
  more accurate row estimation
  for RANGE scan
mysql-test/r/range.result:
  added test case for bug #1724
  'WHERE ... IN() optimizer behaviour has changed since 4.0.14'
mysql-test/r/select.result:
  please ignore
mysql-test/t/range.test:
  added test case for bug #1724
  'WHERE ... IN() optimizer behaviour has changed since 4.0.14'
sql/sql_select.cc:
  fix for bug #1724 'WHERE ... IN() optimizer behaviour 
  has changed since 4.0.14'
  We need to calculate cost of RANGE
  scan instead of cost of FULL scan
  if RANGE is present
  Few comments cleaned up.
This commit is contained in:
unknown
2003-11-03 19:56:01 +03:00
parent 15cc0ad2ec
commit 22bc137c2e
5 changed files with 87 additions and 28 deletions
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6
mysql-test/r/order_by.result
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@ -307,17 +307,17 @@ table type possible_keys key key_len ref rows Extra
t1 range a a 9 NULL 8 Using where; Using index
explain select * from t1 where a = 2 and b >0 order by a desc,b desc;
table type possible_keys key key_len ref rows Extra
t1 range a a 9 NULL 5 Using where; Using index
t1 range a a 9 NULL 4 Using where; Using index
explain select * from t1 where a = 2 and b is null order by a desc,b desc;
table type possible_keys key key_len ref rows Extra
t1 ref a a 9 const,const 1 Using where; Using index; Using filesort
explain select * from t1 where a = 2 and (b is null or b > 0) order by a
desc,b desc;
table type possible_keys key key_len ref rows Extra
t1 range a a 9 NULL 6 Using where; Using index
t1 range a a 9 NULL 5 Using where; Using index
explain select * from t1 where a = 2 and b > 0 order by a desc,b desc;
table type possible_keys key key_len ref rows Extra
t1 range a a 9 NULL 5 Using where; Using index
t1 range a a 9 NULL 4 Using where; Using index
explain select * from t1 where a = 2 and b < 2 order by a desc,b desc;
table type possible_keys key key_len ref rows Extra
t1 range a a 9 NULL 2 Using where; Using index

17
mysql-test/r/range.result
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@ -273,3 +273,20 @@ table type possible_keys key key_len ref rows Extra
t2 ref j1 j1 4 const 1 Using where; Using index
t1 ALL i2 NULL NULL NULL 4 Range checked for each record (index map: 2)
DROP TABLE t1,t2;
CREATE TABLE t1 (
a int(11) default NULL,
b int(11) default NULL,
KEY a (a),
KEY b (b)
) TYPE=MyISAM;
INSERT INTO t1 VALUES
(1,1),(2,1),(3,1),(4,1),(5,1),(6,1),(7,1),(8,1),(9,1),(10,2),(10,2),
(13,2),(14,2),(15,2),(16,2),(17,3),(17,3),(16,3),(17,3),(19,3),(20,3),
(21,4),(22,5),(23,5),(24,5),(25,5),(26,5),(30,5),(31,5),(32,5),(33,5),
(33,5),(33,5),(33,5),(33,5),(34,5),(35,5);
EXPLAIN SELECT * FROM t1 WHERE a IN(1,2) AND b=5;
table type possible_keys key key_len ref rows Extra
t1 range a,b a 5 NULL 2 Using where
SELECT * FROM t1 WHERE a IN(1,2) AND b=5;
a b
DROP TABLE t1;

4
mysql-test/r/select.result
View File

@ -2136,10 +2136,10 @@ a a a
select * from (t1 as t2 left join t1 as t3 using (a)) inner join t1 on t1.a>1;
a a a
1 1 2
2 2 2
3 3 2
1 1 3
2 2 2
2 2 3
3 3 2
3 3 3
select * from t1 inner join (t1 as t2 left join t1 as t3 using (a)) on t1.a>1;
a a a

23
mysql-test/t/range.test
View File

@ -214,3 +214,26 @@ explain select * from t1, t2 where (t1.key1 <t2.keya + 1) and t2.keya=3;
explain select * from t1 force index(i2), t2 where (t1.key1 <t2.keya + 1) and t2.keya=3;
DROP TABLE t1,t2;
# bug #1724: use RANGE on more selective column instead of REF on less
# selective
CREATE TABLE t1 (
a int(11) default NULL,
b int(11) default NULL,
KEY a (a),
KEY b (b)
) TYPE=MyISAM;
INSERT INTO t1 VALUES
(1,1),(2,1),(3,1),(4,1),(5,1),(6,1),(7,1),(8,1),(9,1),(10,2),(10,2),
(13,2),(14,2),(15,2),(16,2),(17,3),(17,3),(16,3),(17,3),(19,3),(20,3),
(21,4),(22,5),(23,5),(24,5),(25,5),(26,5),(30,5),(31,5),(32,5),(33,5),
(33,5),(33,5),(33,5),(33,5),(34,5),(35,5);
EXPLAIN SELECT * FROM t1 WHERE a IN(1,2) AND b=5;
SELECT * FROM t1 WHERE a IN(1,2) AND b=5;
DROP TABLE t1;
# we expect that optimizer will choose key on A

35
sql/sql_select.cc
View File

@ -2145,8 +2145,6 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
!(s->table->force_index && best_key))
{ // Check full join
ha_rows rnd_records= s->found_records;
/* Estimate cost of reading table. */
tmp= s->table->file->scan_time();
/*
If there is a restriction on the table, assume that 25% of the
rows can be skipped on next part.
@ -2156,15 +2154,35 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
if (found_constraint)
rnd_records-= rnd_records/4;
/*
Range optimizer never proposes a RANGE if it isn't better
than FULL: so if RANGE is present, it's always preferred to FULL.
Here we estimate its cost.
*/
if (s->quick)
{
/*
For each record we:
- read record range through 'quick'
- skip rows which does not satisfy WHERE constraints
*/
tmp= record_count *
(s->quick->read_time +
(s->found_records - rnd_records)/(double) TIME_FOR_COMPARE);
}
else
{
/* Estimate cost of reading table. */
tmp= s->table->file->scan_time();
if (s->on_expr) // Can't use join cache
{
tmp= record_count *
/* We have to read the whole table for each record */
(tmp +
/*
And we have to skip rows which does not satisfy join
condition for each record.
For each record we have to:
- read the whole table record
- skip rows which does not satisfy join condition
*/
tmp= record_count *
(tmp +
(s->records - rnd_records)/(double) TIME_FOR_COMPARE);
}
else
@ -2182,10 +2200,11 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
*/
tmp+= (s->records - rnd_records)/(double) TIME_FOR_COMPARE;
}
}
/*
We estimate the cost of evaluating WHERE clause for found records
as record_count * rnd_records + TIME_FOR_COMPARE. This cost plus
as record_count * rnd_records / TIME_FOR_COMPARE. This cost plus
tmp give us total cost of using TABLE SCAN
*/
if (best == DBL_MAX ||