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func_group.result, func_group.test: 

  Added tests for extended max/min optimization
opt_sum.cc:
  Extended min/max optimization


sql/opt_sum.cc:
  Extended min/max optimization
mysql-test/t/func_group.test:
  Added tests for extended max/min optimization
mysql-test/r/func_group.result:
  Added tests for extended max/min optimization
parent ea058779
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mysql-test/r/func_group.result
View file @ c015eb9c
...@@ -179,6 +179,17 @@ explain select max(t1.a1), max(t2.a2) from t1, t2; ...@@ -179,6 +179,17 @@ explain select max(t1.a1), max(t2.a2) from t1, t2;
id select_type table type possible_keys key key_len ref rows Extra id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL No matching min/max row 1 SIMPLE NULL NULL NULL NULL NULL NULL NULL No matching min/max row
insert into t2 values('AAA', 10, 0.5); insert into t2 values('AAA', 10, 0.5);
insert into t2 values('BBB', 20, 1.0);
select t1.a1, t1.a2, t2.a1, t2.a2 from t1,t2;
a1 a2 a1 a2
10 aaa AAA 10
10 NULL AAA 10
10 bbb AAA 10
20 zzz AAA 10
10 aaa BBB 20
10 NULL BBB 20
10 bbb BBB 20
20 zzz BBB 20
select max(t1.a1), max(t2.a1) from t1, t2 where t2.a2=9; select max(t1.a1), max(t2.a1) from t1, t2 where t2.a2=9;
max(t1.a1) max(t2.a1) max(t1.a1) max(t2.a1)
NULL NULL NULL NULL
...@@ -188,19 +199,252 @@ NULL NULL ...@@ -188,19 +199,252 @@ NULL NULL
select t1.a1, t1.a2, t2.a1, t2.a2 from t1 left outer join t2 on t1.a1=10; select t1.a1, t1.a2, t2.a1, t2.a2 from t1 left outer join t2 on t1.a1=10;
a1 a2 a1 a2 a1 a2 a1 a2
10 aaa AAA 10 10 aaa AAA 10
10 aaa BBB 20
10 NULL AAA 10 10 NULL AAA 10
10 NULL BBB 20
10 bbb AAA 10 10 bbb AAA 10
10 bbb BBB 20
20 zzz NULL NULL 20 zzz NULL NULL
select max(t1.a2) from t1 left outer join t2 on t1.a1=10; select max(t1.a2) from t1 left outer join t2 on t1.a1=10;
max(t1.a2) max(t1.a2)
zzz zzz
select max(t1.a2) from t1 left outer join t2 on t1.a1=10 where t1.a1=20; select max(t2.a1) from t2 left outer join t1 on t2.a2=10 where t2.a2=20;
max(t1.a2) max(t2.a1)
zzz BBB
select max(t1.a2) from t1 left outer join t2 on t1.a1=10 where t1.a1=10; select max(t2.a1) from t2 left outer join t1 on t2.a2=10 where t2.a2=10;
max(t1.a2) max(t2.a1)
bbb AAA
select max(t2.a1) from t1 left outer join t2 on t1.a2=t2.a1 and 1=0 where t2.a1='AAA'; select max(t2.a1) from t1 left outer join t2 on t1.a2=t2.a1 and 1=0 where t2.a1='AAA';
max(t2.a1) max(t2.a1)
NULL NULL
select max(t1.a2),max(t2.a1) from t1 left outer join t2 on t1.a1=10;
max(t1.a2) max(t2.a1)
zzz BBB
drop table t1,t2; drop table t1,t2;
create table t1(
a1 char(3) primary key,
a2 smallint,
a3 char(3),
a4 real,
a5 date,
key k1(a2,a3),
key k2(a4 desc,a1),
key k3(a5,a1)
);
create table t2(
a1 char(3) primary key,
a2 char(17),
a3 char(2),
a4 char(3),
key k1(a3, a2),
key k2(a4)
);
insert into t1 values('AME',0,'SEA',0.100,date'1942-02-19');
insert into t1 values('HBR',1,'SEA',0.085,date'1948-03-05');
insert into t1 values('BOT',2,'SEA',0.085,date'1951-11-29');
insert into t1 values('BMC',3,'SEA',0.085,date'1958-09-08');
insert into t1 values('TWU',0,'LAX',0.080,date'1969-10-05');
insert into t1 values('BDL',0,'DEN',0.080,date'1960-11-27');
insert into t1 values('DTX',1,'NYC',0.080,date'1961-05-04');
insert into t1 values('PLS',1,'WDC',0.075,date'1949-01-02');
insert into t1 values('ZAJ',2,'CHI',0.075,date'1960-06-15');
insert into t1 values('VVV',2,'MIN',0.075,date'1959-06-28');
insert into t1 values('GTM',3,'DAL',0.070,date'1977-09-23');
insert into t1 values('SSJ',null,'CHI',null,date'1974-03-19');
insert into t1 values('KKK',3,'ATL',null,null);
insert into t1 values('XXX',null,'MIN',null,null);
insert into t2 values('TKF','Seattle','WA','AME');
insert into t2 values('LCC','Los Angeles','CA','TWU');
insert into t2 values('DEN','Denver','CO','BDL');
insert into t2 values('SDC','San Diego','CA','TWU');
insert into t2 values('NOL','New Orleans','LA','GTM');
insert into t2 values('LAK','Los Angeles','CA','TWU');
select * from t1;
a1 a2 a3 a4 a5
AME 0 SEA 0.1 1942-02-19
HBR 1 SEA 0.085 1948-03-05
BOT 2 SEA 0.085 1951-11-29
BMC 3 SEA 0.085 1958-09-08
TWU 0 LAX 0.08 1969-10-05
BDL 0 DEN 0.08 1960-11-27
DTX 1 NYC 0.08 1961-05-04
PLS 1 WDC 0.075 1949-01-02
ZAJ 2 CHI 0.075 1960-06-15
VVV 2 MIN 0.075 1959-06-28
GTM 3 DAL 0.07 1977-09-23
SSJ NULL CHI NULL 1974-03-19
KKK 3 ATL NULL NULL
XXX NULL MIN NULL NULL
select * from t2;
a1 a2 a3 a4
TKF Seattle WA AME
LCC Los Angeles CA TWU
DEN Denver CO BDL
SDC San Diego CA TWU
NOL New Orleans LA GTM
LAK Los Angeles CA TWU
explain
select min(a1) from t1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select min(a1) from t1;
min(a1)
AME
explain
select max(a4) from t1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select max(a4) from t1;
max(a4)
0.1
explain
select min(a5), max(a5) from t1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select min(a5), max(a5) from t1;
min(a5) max(a5)
1942-02-19 1977-09-23
explain
select min(a3) from t1 where a2 = 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select min(a3) from t1 where a2 = 2;
min(a3)
CHI
explain
select min(a1), max(a1) from t1 where a4 = 0.080;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select min(a1), max(a1) from t1 where a4 = 0.080;
min(a1) max(a1)
BDL TWU
explain
select min(t1.a5), max(t2.a3) from t1, t2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select min(t1.a5), max(t2.a3) from t1, t2;
min(t1.a5) max(t2.a3)
1942-02-19 WA
explain
select min(t1.a3), max(t2.a2) from t1, t2 where t1.a2 = 0 and t2.a3 = 'CA';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select min(t1.a3), max(t2.a2) from t1, t2 where t1.a2 = 0 and t2.a3 = 'CA';
min(t1.a3) max(t2.a2)
DEN San Diego
explain
select min(a1) from t1 where a1 > 'KKK';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select min(a1) from t1 where a1 > 'KKK';
min(a1)
PLS
explain
select min(a1) from t1 where a1 >= 'KKK';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select min(a1) from t1 where a1 >= 'KKK';
min(a1)
KKK
explain
select max(a3) from t1 where a2 = 2 and a3 < 'SEA';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select max(a3) from t1 where a2 = 2 and a3 < 'SEA';
max(a3)
MIN
explain
select max(a5) from t1 where a5 < date'1970-01-01';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select max(a5) from t1 where a5 < date'1970-01-01';
max(a5)
1969-10-05
explain
select max(a3) from t1 where a2 is null;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select max(a3) from t1 where a2 is null;
max(a3)
MIN
explain
select max(a3) from t1 where a2 = 0 and a3 between 'K' and 'Q';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select max(a3) from t1 where a2 = 0 and a3 between 'K' and 'Q';
max(a3)
LAX
explain
select min(a1), max(a1) from t1 where a1 between 'A' and 'P';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select min(a1), max(a1) from t1 where a1 between 'A' and 'P';
min(a1) max(a1)
AME KKK
explain
select max(a3) from t1 where a3 < 'SEA' and a2 = 2 and a3 <= 'MIN';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select max(a3) from t1 where a3 < 'SEA' and a2 = 2 and a3 <= 'MIN';
max(a3)
MIN
explain
select max(a3) from t1 where a3 = 'SEA' and a2 = 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select max(a3) from t1 where a3 = 'SEA' and a2 = 2;
max(a3)
SEA
explain
select max(a3) from t1 where a3 = 'DEN' and a2 = 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL No matching min/max row
select max(a3) from t1 where a3 = 'DEN' and a2 = 2;
max(a3)
NULL
explain
select max(t1.a3), min(t2.a2) from t1, t2 where t1.a2 = 2 and t1.a3 < 'MIN' and t2.a3 = 'CA';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select max(t1.a3), min(t2.a2) from t1, t2 where t1.a2 = 2 and t1.a3 < 'MIN' and t2.a3 = 'CA';
max(t1.a3) min(t2.a2)
CHI Los Angeles
explain
select max(a3) from t1 where a2 is null and a2 = 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
select max(a3) from t1 where a2 is null and a2 = 2;
max(a3)
NULL
explain
select max(a2) from t1 where a2 >= 1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select max(a2) from t1 where a2 >= 1;
max(a2)
3
explain
select min(a3) from t1 where a2 = 2 and a3 < 'SEA';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select min(a3) from t1 where a2 = 2 and a3 < 'SEA';
min(a3)
CHI
explain
select min(a1) from t1 where a1 > 'KKK' or a1 < 'XXX';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range PRIMARY PRIMARY 0 NULL 15 Using where; Using index
explain
select min(a1) from t1 where a1 != 'KKK';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL PRIMARY 3 NULL 14 Using where; Using index
explain
select max(a3) from t1 where a2 < 2 and a3 < 'SEA';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range k1 k1 3 NULL 5 Using where; Using index
explain
select max(t1.a3), min(t2.a2) from t1, t2 where t1.a2 = 2 and t1.a3 < 'MIN' and t2.a3 > 'CA';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range k1 k1 7 NULL 1 Using where; Using index
1 SIMPLE t2 range k1 k1 3 NULL 4 Using where; Using index
drop table if exists t1, t2;
mysql-test/t/func_group.test
View file @ c015eb9c
...@@ -121,11 +121,158 @@ explain select min(a2) from t1; ...@@ -121,11 +121,158 @@ explain select min(a2) from t1;
explain select max(t1.a1), max(t2.a2) from t1, t2; explain select max(t1.a1), max(t2.a2) from t1, t2;
insert into t2 values('AAA', 10, 0.5); insert into t2 values('AAA', 10, 0.5);
insert into t2 values('BBB', 20, 1.0);
select t1.a1, t1.a2, t2.a1, t2.a2 from t1,t2;
select max(t1.a1), max(t2.a1) from t1, t2 where t2.a2=9; select max(t1.a1), max(t2.a1) from t1, t2 where t2.a2=9;
select max(t2.a1), max(t1.a1) from t1, t2 where t2.a2=9; select max(t2.a1), max(t1.a1) from t1, t2 where t2.a2=9;
select t1.a1, t1.a2, t2.a1, t2.a2 from t1 left outer join t2 on t1.a1=10; select t1.a1, t1.a2, t2.a1, t2.a2 from t1 left outer join t2 on t1.a1=10;
select max(t1.a2) from t1 left outer join t2 on t1.a1=10; select max(t1.a2) from t1 left outer join t2 on t1.a1=10;
select max(t1.a2) from t1 left outer join t2 on t1.a1=10 where t1.a1=20; select max(t2.a1) from t2 left outer join t1 on t2.a2=10 where t2.a2=20;
select max(t1.a2) from t1 left outer join t2 on t1.a1=10 where t1.a1=10; select max(t2.a1) from t2 left outer join t1 on t2.a2=10 where t2.a2=10;
select max(t2.a1) from t1 left outer join t2 on t1.a2=t2.a1 and 1=0 where t2.a1='AAA'; select max(t2.a1) from t1 left outer join t2 on t1.a2=t2.a1 and 1=0 where t2.a1='AAA';
select max(t1.a2),max(t2.a1) from t1 left outer join t2 on t1.a1=10;
drop table t1,t2; drop table t1,t2;
#
# Tests to check MIN/MAX query optimization
#
# Create database schema
create table t1(
a1 char(3) primary key,
a2 smallint,
a3 char(3),
a4 real,
a5 date,
key k1(a2,a3),
key k2(a4 desc,a1),
key k3(a5,a1)
);
create table t2(
a1 char(3) primary key,
a2 char(17),
a3 char(2),
a4 char(3),
key k1(a3, a2),
key k2(a4)
);
# Populate table t1
insert into t1 values('AME',0,'SEA',0.100,date'1942-02-19');
insert into t1 values('HBR',1,'SEA',0.085,date'1948-03-05');
insert into t1 values('BOT',2,'SEA',0.085,date'1951-11-29');
insert into t1 values('BMC',3,'SEA',0.085,date'1958-09-08');
insert into t1 values('TWU',0,'LAX',0.080,date'1969-10-05');
insert into t1 values('BDL',0,'DEN',0.080,date'1960-11-27');
insert into t1 values('DTX',1,'NYC',0.080,date'1961-05-04');
insert into t1 values('PLS',1,'WDC',0.075,date'1949-01-02');
insert into t1 values('ZAJ',2,'CHI',0.075,date'1960-06-15');
insert into t1 values('VVV',2,'MIN',0.075,date'1959-06-28');
insert into t1 values('GTM',3,'DAL',0.070,date'1977-09-23');
insert into t1 values('SSJ',null,'CHI',null,date'1974-03-19');
insert into t1 values('KKK',3,'ATL',null,null);
insert into t1 values('XXX',null,'MIN',null,null);
# Populate table t2
insert into t2 values('TKF','Seattle','WA','AME');
insert into t2 values('LCC','Los Angeles','CA','TWU');
insert into t2 values('DEN','Denver','CO','BDL');
insert into t2 values('SDC','San Diego','CA','TWU');
insert into t2 values('NOL','New Orleans','LA','GTM');
insert into t2 values('LAK','Los Angeles','CA','TWU');
# Show the table contents
select * from t1;
select * from t2;
# Queries with min/max functions
# which regular min/max optimization are applied to
explain
select min(a1) from t1;
select min(a1) from t1;
explain
select max(a4) from t1;
select max(a4) from t1;
explain
select min(a5), max(a5) from t1;
select min(a5), max(a5) from t1;
explain
select min(a3) from t1 where a2 = 2;
select min(a3) from t1 where a2 = 2;
explain
select min(a1), max(a1) from t1 where a4 = 0.080;
select min(a1), max(a1) from t1 where a4 = 0.080;
explain
select min(t1.a5), max(t2.a3) from t1, t2;
select min(t1.a5), max(t2.a3) from t1, t2;
explain
select min(t1.a3), max(t2.a2) from t1, t2 where t1.a2 = 0 and t2.a3 = 'CA';
select min(t1.a3), max(t2.a2) from t1, t2 where t1.a2 = 0 and t2.a3 = 'CA';
# Queries with min/max functions
# which extended min/max optimization are applied to
explain
select min(a1) from t1 where a1 > 'KKK';
select min(a1) from t1 where a1 > 'KKK';
explain
select min(a1) from t1 where a1 >= 'KKK';
select min(a1) from t1 where a1 >= 'KKK';
explain
select max(a3) from t1 where a2 = 2 and a3 < 'SEA';
select max(a3) from t1 where a2 = 2 and a3 < 'SEA';
explain
select max(a5) from t1 where a5 < date'1970-01-01';
select max(a5) from t1 where a5 < date'1970-01-01';
explain
select max(a3) from t1 where a2 is null;
select max(a3) from t1 where a2 is null;
explain
select max(a3) from t1 where a2 = 0 and a3 between 'K' and 'Q';
select max(a3) from t1 where a2 = 0 and a3 between 'K' and 'Q';
explain
select min(a1), max(a1) from t1 where a1 between 'A' and 'P';
select min(a1), max(a1) from t1 where a1 between 'A' and 'P';
explain
select max(a3) from t1 where a3 < 'SEA' and a2 = 2 and a3 <= 'MIN';
select max(a3) from t1 where a3 < 'SEA' and a2 = 2 and a3 <= 'MIN';
explain
select max(a3) from t1 where a3 = 'SEA' and a2 = 2;
select max(a3) from t1 where a3 = 'SEA' and a2 = 2;
explain
select max(a3) from t1 where a3 = 'DEN' and a2 = 2;
select max(a3) from t1 where a3 = 'DEN' and a2 = 2;
explain
select max(t1.a3), min(t2.a2) from t1, t2 where t1.a2 = 2 and t1.a3 < 'MIN' and t2.a3 = 'CA';
select max(t1.a3), min(t2.a2) from t1, t2 where t1.a2 = 2 and t1.a3 < 'MIN' and t2.a3 = 'CA';
explain
select max(a3) from t1 where a2 is null and a2 = 2;
select max(a3) from t1 where a2 is null and a2 = 2;
explain
select max(a2) from t1 where a2 >= 1;
select max(a2) from t1 where a2 >= 1;
explain
select min(a3) from t1 where a2 = 2 and a3 < 'SEA';
select min(a3) from t1 where a2 = 2 and a3 < 'SEA';
# Queries to which max/min optimization is not applied
explain
select min(a1) from t1 where a1 > 'KKK' or a1 < 'XXX';
explain
select min(a1) from t1 where a1 != 'KKK';
explain
select max(a3) from t1 where a2 < 2 and a3 < 'SEA';
explain
select max(t1.a3), min(t2.a2) from t1, t2 where t1.a2 = 2 and t1.a3 < 'MIN' and t2.a3 > 'CA';
# Clean up
drop table if exists t1, t2;
\ No newline at end of file
sql/opt_sum.cc
View file @ c015eb9c
...@@ -15,12 +15,44 @@ ...@@ -15,12 +15,44 @@
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
/* Optimizing of many different type of queries with GROUP functions */ /*
Optimising of MIN(), MAX() and COUNT(*) queries without 'group by' clause
by replacing the aggregate expression with a constant.
Given a table with a compound key on columns (a,b,c), the following
types of queries are optimised (assuming the table handler supports
the required methods)
SELECT COUNT(*) FROM t1[,t2,t3,...]
SELECT MIN(b) FROM t1 WHERE a=const
SELECT MAX(c) FROM t1 WHERE a=const AND b=const
SELECT MAX(b) FROM t1 WHERE a=const AND b<const
SELECT MIN(b) FROM t1 WHERE a=const AND b>const
SELECT MIN(b) FROM t1 WHERE a=const AND b BETWEEN const AND const
SELECT MAX(b) FROM t1 WHERE a=const AND b BETWEEN const AND const
Instead of '<' one can use '<=', '>', '>=' and '=' as well.
Instead of 'a=const' the condition 'a IS NULL' can be used.
If all selected fields are replaced then we will also remove all
involved tables and return the answer without any join. Thus, the
following query will be replaced with a row of two constants:
SELECT MAX(b), MIN(d) FROM t1,t2
WHERE a=const AND b<const AND d>const
(assuming a index for column d of table t2 is defined)
*/
#include "mysql_priv.h" #include "mysql_priv.h"
#include "sql_select.h" #include "sql_select.h"
static bool find_range_key(TABLE_REF *ref, Field* field,COND *cond); static bool find_key_for_maxmin(bool max_fl, TABLE_REF *ref,
Field* field, COND *cond,
uint *range_fl, uint *key_prefix_length);
static int reckey_in_range(bool max_fl, TABLE_REF *ref, Field* field,
COND *cond, uint range_fl, uint prefix_len);
static int maxmin_in_range(bool max_fl, Field* field, COND *cond);
/* /*
Substitutes constants for some COUNT(), MIN() and MAX() functions. Substitutes constants for some COUNT(), MIN() and MAX() functions.
...@@ -92,14 +124,14 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds) ...@@ -92,14 +124,14 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds)
*/ */
if (!conds && !((Item_sum_count*) item)->args[0]->maybe_null) if (!conds && !((Item_sum_count*) item)->args[0]->maybe_null)
{ {
longlong count=1; longlong count= 1;
TABLE_LIST *table; TABLE_LIST *table;
for (table=tables; table ; table=table->next) for (table=tables ; table ; table=table->next)
{ {
if (outer_tables || (table->table->file->table_flags() & if (outer_tables || (table->table->file->table_flags() &
HA_NOT_EXACT_COUNT)) HA_NOT_EXACT_COUNT))
{ {
const_result=0; // Can't optimize left join const_result= 0; // Can't optimize left join
break; break;
} }
tables->table->file->info(HA_STATUS_VARIABLE | HA_STATUS_NO_LOCK); tables->table->file->info(HA_STATUS_VARIABLE | HA_STATUS_NO_LOCK);
...@@ -108,11 +140,11 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds) ...@@ -108,11 +140,11 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds)
if (!table) if (!table)
{ {
((Item_sum_count*) item)->make_const(count); ((Item_sum_count*) item)->make_const(count);
recalc_const_item=1; recalc_const_item= 1;
} }
} }
else else
const_result=0; const_result= 0;
break; break;
case Item_sum::MIN_FUNC: case Item_sum::MIN_FUNC:
{ {
...@@ -126,39 +158,49 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds) ...@@ -126,39 +158,49 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds)
{ {
byte key_buff[MAX_KEY_LENGTH]; byte key_buff[MAX_KEY_LENGTH];
TABLE_REF ref; TABLE_REF ref;
ref.key_buff=key_buff; uint range_fl, prefix_len;
ref.key_buff= key_buff;
Item_field *item_field= ((Item_field*) expr); Item_field *item_field= ((Item_field*) expr);
TABLE *table= item_field->field->table; TABLE *table= item_field->field->table;
/*
Look for a partial key that can be used for optimization.
If we succeed, ref.key_length will contain the length of
this key, while prefix_len will contain the length of
the beginning of this key without field used in MIN()
*/
if ((outer_tables & table->map) || if ((outer_tables & table->map) ||
(!find_range_key(&ref, item_field->field,conds))) !find_key_for_maxmin(0, &ref, item_field->field, conds,
&range_fl, &prefix_len))
{ {
const_result=0; const_result= 0;
break; break;
} }
bool error= table->file->index_init((uint) ref.key); bool error= table->file->index_init((uint) ref.key);
enum ha_rkey_function find_flag= HA_READ_KEY_OR_NEXT; enum ha_rkey_function find_flag= range_fl & NEAR_MIN ?
uint prefix_len= ref.key_length; HA_READ_AFTER_KEY : HA_READ_KEY_OR_NEXT;
/* /*
If we are doing MIN() on a column with NULL fields If we are doing MIN() on a column with NULL fields
we must read the key after the NULL column we must read the key after the NULL column
*/ */
if (item_field->field->null_bit) if (item_field->field->null_bit)
{ {
ref.key_buff[ref.key_length++]=1; ref.key_buff[ref.key_length++]= 1;
find_flag= HA_READ_AFTER_KEY; find_flag= HA_READ_AFTER_KEY;
} }
if (!ref.key_length) if (!ref.key_length)
error=table->file->index_first(table->record[0]) !=0; error= table->file->index_first(table->record[0]) != 0;
else else
error=table->file->index_read(table->record[0],key_buff, error= table->file->index_read(table->record[0], key_buff,
ref.key_length, ref.key_length,
find_flag) || find_flag) ||
key_cmp(table, key_buff, ref.key, prefix_len); reckey_in_range(0, &ref, item_field->field,
conds, range_fl, prefix_len);
if (table->key_read) if (table->key_read)
{ {
table->key_read=0; table->key_read= 0;
table->file->extra(HA_EXTRA_NO_KEYREAD); table->file->extra(HA_EXTRA_NO_KEYREAD);
} }
table->file->index_end(); table->file->index_end();
...@@ -168,12 +210,12 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds) ...@@ -168,12 +210,12 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds)
} }
else if (!expr->const_item()) // This is VERY seldom false else if (!expr->const_item()) // This is VERY seldom false
{ {
const_result=0; const_result= 0;
break; break;
} }
((Item_sum_min*) item_sum)->reset(); ((Item_sum_min*) item_sum)->reset();
((Item_sum_min*) item_sum)->make_const(); ((Item_sum_min*) item_sum)->make_const();
recalc_const_item=1; recalc_const_item= 1;
break; break;
} }
case Item_sum::MAX_FUNC: case Item_sum::MAX_FUNC:
...@@ -188,31 +230,42 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds) ...@@ -188,31 +230,42 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds)
{ {
byte key_buff[MAX_KEY_LENGTH]; byte key_buff[MAX_KEY_LENGTH];
TABLE_REF ref; TABLE_REF ref;
ref.key_buff=key_buff; uint range_fl, prefix_len;
TABLE *table=((Item_field*) expr)->field->table;
ref.key_buff= key_buff;
Item_field *item_field= ((Item_field*) expr);
TABLE *table= item_field->field->table;
/*
Look for a partial key that can be used for optimization.
If we succeed, ref.key_length will contain the length of
this key, while prefix_len will contain the length of
the beginning of this key without field used in MAX()
*/
if ((outer_tables & table->map) || if ((outer_tables & table->map) ||
!find_range_key(&ref, ((Item_field*) expr)->field,conds)) !find_key_for_maxmin(1, &ref, item_field->field, conds,
&range_fl, &prefix_len))
{ {
const_result=0; const_result= 0;
break; break;
} }
if ((table->file->table_flags() & HA_NOT_READ_AFTER_KEY)) if ((table->file->table_flags() & HA_NOT_READ_AFTER_KEY))
{ {
const_result=0; const_result= 0;
break; break;
} }
bool error=table->file->index_init((uint) ref.key); bool error= table->file->index_init((uint) ref.key);
if (!ref.key_length) if (!ref.key_length)
error=table->file->index_last(table->record[0]) !=0; error=table->file->index_last(table->record[0]) != 0;
else else
{ error= table->file->index_read(table->record[0], key_buff,
error = table->file->index_read(table->record[0], key_buff,
ref.key_length, ref.key_length,
HA_READ_PREFIX_LAST) || range_fl & NEAR_MAX ?
key_cmp(table,key_buff,ref.key,ref.key_length); HA_READ_BEFORE_KEY :
} HA_READ_PREFIX_LAST_OR_PREV) ||
reckey_in_range(1, &ref, item_field->field,
conds, range_fl, prefix_len);
if (table->key_read) if (table->key_read)
{ {
table->key_read=0; table->key_read=0;
...@@ -225,16 +278,16 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds) ...@@ -225,16 +278,16 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds)
} }
else if (!expr->const_item()) // This is VERY seldom false else if (!expr->const_item()) // This is VERY seldom false
{ {
const_result=0; const_result= 0;
break; break;
} }
((Item_sum_min*) item_sum)->reset(); ((Item_sum_min*) item_sum)->reset();
((Item_sum_min*) item_sum)->make_const(); ((Item_sum_min*) item_sum)->make_const();
recalc_const_item=1; recalc_const_item= 1;
break; break;
} }
default: default:
const_result=0; const_result= 0;
break; break;
} }
} }
...@@ -243,13 +296,13 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds) ...@@ -243,13 +296,13 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds)
if (recalc_const_item) if (recalc_const_item)
item->update_used_tables(); item->update_used_tables();
if (!item->const_item()) if (!item->const_item())
const_result=0; const_result= 0;
} }
} }
/* /*
If we have a where clause, we can only ignore searching in the If we have a where clause, we can only ignore searching in the
tables if MIN/MAX optimisation replaced all used tables tables if MIN/MAX optimisation replaced all used tables
This is to not to use replaced values in case of: We do not use replaced values in case of:
SELECT MIN(key) FROM table_1, empty_table SELECT MIN(key) FROM table_1, empty_table
removed_tables is != 0 if we have used MIN() or MAX(). removed_tables is != 0 if we have used MIN() or MAX().
*/ */
...@@ -258,178 +311,455 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds) ...@@ -258,178 +311,455 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds)
return const_result; return const_result;
} }
/* Count in how many times table is used (up to MAX_KEY_PARTS+1) */
uint count_table_entries(COND *cond,TABLE *table) /*
{ Test if the predicate compares a field with constants
if (cond->type() == Item::COND_ITEM)
{
if (((Item_cond*) cond)->functype() == Item_func::COND_OR_FUNC)
return (cond->used_tables() & table->map) ? MAX_REF_PARTS+1 : 0;
List_iterator_fast<Item> li(*((Item_cond*) cond)->argument_list()); SYNOPSIS
simple_pred()
func_item in: Predicate item
args out: Here we store the field followed by constants
inv_order out: Is set to 1 if the predicate is of the form 'const op field'
RETURN
0 func_item is a simple predicate: a field is compared with constants
1 Otherwise
*/
static bool simple_pred(Item_func *func_item, Item **args, bool *inv_order)
{
Item *item; Item *item;
uint count=0; *inv_order= 0;
while ((item=li++)) switch (func_item->argument_count()) {
case 1:
/* field IS NULL */
item= func_item->arguments()[0];
if (item->type() != Item::FIELD_ITEM)
return 0;
args[0]= item;
break;
case 2:
/* 'field op const' or 'const op field' */
item= func_item->arguments()[0];
if (item->type() == Item::FIELD_ITEM)
{ {
if ((count+=count_table_entries(item,table)) > MAX_REF_PARTS) args[0]= item;
return MAX_REF_PARTS+1; item= func_item->arguments()[1];
if (!item->const_item())
return 0;
args[1]= item;
} }
return count; else if (item->const_item())
{
args[1]= item;
item= func_item->arguments()[1];
if (item->type() != Item::FIELD_ITEM)
return 0;
args[0]= item;
*inv_order= 1;
} }
if (cond->type() == Item::FUNC_ITEM && else
(((Item_func*) cond)->functype() == Item_func::EQ_FUNC || return 0;
(((Item_func*) cond)->functype() == Item_func::EQUAL_FUNC)) && break;
cond->used_tables() == table->map) case 3:
/* field BETWEEN const AND const */
item= func_item->arguments()[0];
if (item->type() == Item::FIELD_ITEM)
{ {
Item *left_item= ((Item_func*) cond)->arguments()[0]; args[0]= item;
Item *right_item= ((Item_func*) cond)->arguments()[1]; for (int i= 1 ; i <= 2; i++)
if (left_item->type() == Item::FIELD_ITEM)
{ {
if (!(((Item_field*) left_item)->field->flags & PART_KEY_FLAG) || item= func_item->arguments()[i];
!right_item->const_item()) if (!item->const_item())
return MAX_REF_PARTS+1; return 0;
return 1; args[i]= item;
} }
if (right_item->type() == Item::FIELD_ITEM)
{
if (!(((Item_field*) right_item)->field->flags & PART_KEY_FLAG) ||
!left_item->const_item())
return MAX_REF_PARTS+1;
return 1;
} }
else
return 0;
} }
return (cond->used_tables() & table->map) ? MAX_REF_PARTS+1 : 0; return 1;
} }
/* check that the field is usable as key part */ /*
Check whether a condition matches a key to get {MAX|MIN}(field):
SYNOPSIS
matching_cond()
max_fl in: Set to 1 if we are optimising MAX()
ref in/out: Reference to the structure we store the key value
keyinfo in Reference to the key info
field_part in: Pointer to the key part for the field
cond in WHERE condition
key_part_used in/out: Map of matchings parts
range_fl in/out: Says whether including key will be used
prefix_len out: Length of common key part for the range
where MAX/MIN is searched for
DESCRIPTION
For the index specified by the keyinfo parameter, index that
contains field as its component (field_part), the function
checks whether the condition cond is a conjunction and all its
conjuncts referring to the columns of the same table as column
field are one of the following forms:
- f_i= const_i or const_i= f_i or f_i is null,
where f_i is part of the index
- field {<|<=|>=|>|=} const or const {<|<=|>=|>|=} field
- field between const1 and const2
RETURN
0 Index can't be used.
1 We can use index to get MIN/MAX value
*/
bool part_of_cond(COND *cond,Field *field) static bool matching_cond(bool max_fl, TABLE_REF *ref, KEY *keyinfo,
KEY_PART_INFO *field_part, COND *cond,
key_part_map *key_part_used, uint *range_fl,
uint *prefix_len)
{ {
if (!cond)
return 1;
Field *field= field_part->field;
if (!(cond->used_tables() & field->table->map))
{
/* Condition doesn't restrict the used table */
return 1;
}
if (cond->type() == Item::COND_ITEM) if (cond->type() == Item::COND_ITEM)
{ {
if (((Item_cond*) cond)->functype() == Item_func::COND_OR_FUNC) if (((Item_cond*) cond)->functype() == Item_func::COND_OR_FUNC)
return 0; // Already checked return 0;
/* AND */
List_iterator_fast<Item> li(*((Item_cond*) cond)->argument_list()); List_iterator_fast<Item> li(*((Item_cond*) cond)->argument_list());
Item *item; Item *item;
while ((item=li++)) while ((item= li++))
{ {
if (part_of_cond(item,field)) if (!matching_cond(max_fl, ref, keyinfo, field_part, item,
key_part_used, range_fl, prefix_len))
return 0;
}
return 1; return 1;
} }
if (cond->type() != Item::FUNC_ITEM)
return 0; // Not operator, can't optimize
bool eq_type= 0; // =, <=> or IS NULL
bool noeq_type= 0; // < or >
bool less_fl= 0; // < or <=
bool is_null= 0;
bool between= 0;
switch (((Item_func*) cond)->functype()) {
case Item_func::ISNULL_FUNC:
is_null= 1; /* fall through */
case Item_func::EQ_FUNC:
case Item_func::EQUAL_FUNC:
eq_type= 1;
break;
case Item_func::LT_FUNC:
noeq_type= 1; /* fall through */
case Item_func::LE_FUNC:
less_fl= 1;
break;
case Item_func::GT_FUNC:
noeq_type= 1; /* fall through */
case Item_func::GE_FUNC:
break;
case Item_func::BETWEEN:
between= 1;
break;
default:
return 0; // Can't optimize function
}
Item *args[3];
bool inv;
/* Test if this is a comparison of a field and constant */
if (!simple_pred((Item_func*) cond, args, &inv))
return 0; return 0;
if (inv && !eq_type)
less_fl= 1-less_fl; // Convert '<' -> '>' (etc)
/* Check if field is part of the tested partial key */
byte *key_ptr= ref->key_buff;
KEY_PART_INFO *part;
for (part= keyinfo->key_part;
;
key_ptr+= part++->store_length)
{
if (part > field_part)
return 0; // Field is beyond the tested parts
if (part->field->eq(((Item_field*) args[0])->field))
break; // Found a part od the key for the field
} }
if (cond->type() == Item::FUNC_ITEM &&
(((Item_func*) cond)->functype() == Item_func::EQ_FUNC || bool is_field_part= part == field_part;
((Item_func*) cond)->functype() == Item_func::EQUAL_FUNC) && if (!(is_field_part || eq_type))
cond->used_tables() == field->table->map) return 0;
key_part_map org_key_part_used= *key_part_used;
if (eq_type || between || max_fl == less_fl)
{ {
Item *left_item= ((Item_func*) cond)->arguments()[0]; uint length= (key_ptr-ref->key_buff)+part->store_length;
Item *right_item= ((Item_func*) cond)->arguments()[1]; if (ref->key_length < length)
if (left_item->type() == Item::FIELD_ITEM) /* Ultimately ref->key_length will contain the length of the search key */
ref->key_length= length;
if (!*prefix_len && part+1 == field_part)
*prefix_len= length;
if (is_field_part && eq_type)
*prefix_len= ref->key_length;
*key_part_used|= (key_part_map) 1 << (part - keyinfo->key_part);
}
if (org_key_part_used != *key_part_used ||
(is_field_part &&
(between || max_fl == less_fl) && !cond->val_int()))
{ {
if (((Item_field*) left_item)->field != field || /*
!right_item->const_item()) It's the first predicate for this part or a predicate of the
return 0; following form that moves upper/lower bounds for max/min values:
- field BETWEEN const AND const
- field {<|<=} const, when searching for MAX
- field {>|>=} const, when searching for MIN
*/
if (is_null)
{
part->field->set_null();
*key_ptr= (byte) 1;
} }
else if (right_item->type() == Item::FIELD_ITEM) else
{ {
if (((Item_field*) right_item)->field != field || store_val_in_field(part->field, args[between && max_fl ? 2 : 1]);
!left_item->const_item()) if (part->null_bit)
return 0; *key_ptr++= (byte) test(part->field->is_null());
right_item=left_item; // const item in right part->field->get_key_image((char*) key_ptr, part->length,
part->field->charset(), Field::itRAW);
} }
store_val_in_field(field,right_item); if (is_field_part)
return 1; {
if (between)
*range_fl&= ~(NO_MAX_RANGE | NO_MIN_RANGE);
else
{
*range_fl&= ~(max_fl ? NO_MAX_RANGE : NO_MIN_RANGE);
if (noeq_type)
*range_fl|= (max_fl ? NEAR_MAX : NEAR_MIN);
else
*range_fl&= ~(max_fl ? NEAR_MAX : NEAR_MIN);
} }
return 0; }
}
else if (eq_type)
{
if (!is_null && !cond->val_int() ||
is_null && !test(part->field->is_null()))
return 0; // Impossible test
}
else if (is_field_part)
*range_fl&= ~(max_fl ? NO_MIN_RANGE : NO_MAX_RANGE);
return 1;
} }
/* Check if we can get value for field by using a key */ /*
Check whether we can get value for {max|min}(field) by using a key.
SYNOPSIS
find_key_for_maxmin()
max_fl in: 0 for MIN(field) / 1 for MAX(field)
ref in/out Reference to the structure we store the key value
field in: Field used inside MIN() / MAX()
cond in: WHERE condition
range_fl in/out Bit flags for how to search if key is ok
prefix_len out: Length of prefix for the search range
DESCRIPTION
If where condition is not a conjunction of 0 or more conjuct the
function returns false, otherwise it checks whether there is an
index including field as its k-th component/part such that:
1. for each previous component f_i there is one and only one conjunct
of the form: f_i= const_i or const_i= f_i or f_i is null
2. references to field occur only in conjucts of the form:
field {<|<=|>=|>|=} const or const {<|<=|>=|>|=} field or
field BETWEEN const1 AND const2
3. all references to the columns from the same table as column field
occur only in conjucts mentioned above.
If such an index exists the function through the ref parameter
returns the key value to find max/min for the field using the index,
the length of first (k-1) components of the key and flags saying
how to apply the key for the search max/min value.
(if we have a condition field = const, prefix_len contains the length
of the whole search key)
RETURN
0 Index can not be used to optimize MIN(field)/MAX(field)
1 Can use key to optimize MIN()/MAX()
In this case ref, range_fl and prefix_len are updated
*/
static bool find_range_key(TABLE_REF *ref, Field* field, COND *cond) static bool find_key_for_maxmin(bool max_fl, TABLE_REF *ref,
Field* field, COND *cond,
uint *range_fl, uint *prefix_len)
{ {
if (!(field->flags & PART_KEY_FLAG)) if (!(field->flags & PART_KEY_FLAG))
return 0; // Not part of a key. Skip it return 0; // Not key field
*prefix_len= 0;
TABLE *table=field->table; TABLE *table= field->table;
uint idx=0; uint idx= 0;
KEY *keyinfo,*keyinfo_end;
for (keyinfo= table->key_info, keyinfo_end= keyinfo+table->keys ;
keyinfo != keyinfo_end;
keyinfo++,idx++)
{
if (table->file->index_flags(idx) & HA_WRONG_ASCII_ORDER)
break;
/* Check if some key has field as first key part */ KEY_PART_INFO *part,*part_end;
if ((field->key_start & field->table->keys_in_use_for_query) && key_part_map key_part_to_use= 0;
(! cond || ! (cond->used_tables() & table->map))) for (part= keyinfo->key_part, part_end= part+keyinfo->key_parts ;
part != part_end ;
part++, key_part_to_use= (key_part_to_use << 1) | 1)
{ {
for (key_map key=field->key_start ;;) if (field->eq(part->field))
{ {
for (; !(key & 1) ; idx++) ref->key= idx;
key>>=1; ref->key_length= 0;
if (!(table->file->index_flags(idx) & HA_WRONG_ASCII_ORDER)) key_part_map key_part_used= 0;
break; // Key is ok *range_fl= NO_MIN_RANGE | NO_MAX_RANGE;
/* Can't use this key, for looking up min() or max(), end if last one */ if (matching_cond(max_fl, ref, keyinfo, part, cond,
if (key == 1) &key_part_used, range_fl, prefix_len) &&
return 0; !(key_part_to_use & ~key_part_used))
{
if (!max_fl && key_part_used == key_part_to_use && part->null_bit)
{
/*
SELECT MIN(key_part2) FROM t1 WHERE key_part1=const
If key_part2 may be NULL, then we want to find the first row
that is not null
*/
ref->key_buff[ref->key_length++]= 1;
*range_fl&= ~NO_MIN_RANGE;
*range_fl|= NEAR_MIN; // > NULL
} }
ref->key_length=0; /*
ref->key=idx; The following test is false when the key in the key tree is
converted (for example to upper case)
*/
if (field->part_of_key & ((key_map) 1 << idx)) if (field->part_of_key & ((key_map) 1 << idx))
{ {
table->key_read=1; table->key_read= 1;
table->file->extra(HA_EXTRA_KEYREAD); table->file->extra(HA_EXTRA_KEYREAD);
} }
return 1; // Ok to use key return 1;
}
}
}
} }
/*
** Check if WHERE consist of exactly the previous key parts for some key
*/
if (!cond)
return 0; return 0;
uint table_entries= count_table_entries(cond,table); }
if (!table_entries || table_entries > MAX_REF_PARTS)
/*
Check whether found key is in range specified by conditions
SYNOPSIS
reckey_in_range()
max_fl in: 0 for MIN(field) / 1 for MAX(field)
ref in: Reference to the key value and info
field in: Field used the MIN/MAX expression
cond in: WHERE condition
range_fl in: Says whether there is a condition to to be checked
prefix_len in: Length of the constant part of the key
RETURN
0 ok
1 WHERE was not true for the found row
*/
static int reckey_in_range(bool max_fl, TABLE_REF *ref, Field* field,
COND *cond, uint range_fl, uint prefix_len)
{
if (key_cmp(field->table, ref->key_buff, ref->key, prefix_len))
return 1;
if (!cond || (range_fl & (max_fl ? NO_MIN_RANGE : NO_MAX_RANGE)))
return 0; return 0;
return maxmin_in_range(max_fl, field, cond);
}
KEY *keyinfo,*keyinfo_end;
idx=0;
for (keyinfo=table->key_info, keyinfo_end=keyinfo+table->keys ;
keyinfo != keyinfo_end;
keyinfo++,idx++)
{
if (table_entries < keyinfo->key_parts)
{
byte *key_ptr=ref->key_buff;
KEY_PART_INFO *part,*part_end;
int left_length=MAX_KEY_LENGTH;
for (part=keyinfo->key_part, part_end=part+table_entries ; /*
part != part_end ; Check whether {MAX|MIN}(field) is in range specified by conditions
part++) SYNOPSIS
{ maxmin_in_range()
if (!part_of_cond(cond,part->field) || max_fl in: 0 for MIN(field) / 1 for MAX(field)
left_length < part->store_length || field in: Field used the MIN/MAX expression
(table->file->index_flags(idx) & HA_WRONG_ASCII_ORDER)) cond in: WHERE condition
break;
// Save found constant RETURN
if (part->null_bit) 0 ok
*key_ptr++= (byte) test(part->field->is_null()); 1 WHERE was not true for the found row
part->field->get_key_image((char*) key_ptr,part->length, */
part->field->charset(), Field::itRAW);
key_ptr+=part->store_length - test(part->null_bit); static int maxmin_in_range(bool max_fl, Field* field, COND *cond)
left_length-=part->store_length; {
} /* If AND/OR condition */
if (part == part_end && part->field == field) if (cond->type() == Item::COND_ITEM)
{ {
ref->key_length= (uint) (key_ptr-ref->key_buff); List_iterator_fast<Item> li(*((Item_cond*) cond)->argument_list());
ref->key=idx; Item *item;
if (field->part_of_key & ((key_map) 1 << idx)) while ((item= li++))
{ {
table->key_read=1; if (maxmin_in_range(max_fl, field, item))
table->file->extra(HA_EXTRA_KEYREAD); return 1;
} }
return 1; // Ok to use key return 0;
} }
if (cond->used_tables() != field->table->map)
return 0;
bool less_fl= 0;
switch (((Item_func*) cond)->functype()) {
case Item_func::BETWEEN:
return cond->val_int() == 0; // Return 1 if WHERE is false
case Item_func::LT_FUNC:
case Item_func::LE_FUNC:
less_fl= 1;
case Item_func::GT_FUNC:
case Item_func::GE_FUNC:
{
Item *item= ((Item_func*) cond)->arguments()[1];
/* In case of 'const op item' we have to swap the operator */
if (!item->const_item())
less_fl= 1-less_fl;
/*
We only have to check the expression if we are using an expression like
SELECT MAX(b) FROM t1 WHERE a=const AND b>const
not for
SELECT MAX(b) FROM t1 WHERE a=const AND b<const
*/
if (max_fl != less_fl)
return cond->val_int() == 0; // Return 1 if WHERE is false
return 0;
} }
case Item_func::EQ_FUNC:
case Item_func::EQUAL_FUNC:
break;
default: // Keep compiler happy
DBUG_ASSERT(1); // Impossible
break;
} }
return 0; // No possible key return 0;
} }
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