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541334c5ac
timestamp: Thu 2011-12-01 15:12:10 +0100 Fix for Bug#13430436 PERFORMANCE DEGRADATION IN SYSBENCH ON INNODB DUE TO ICP When running sysbench on InnoDB there is a performance degradation due to index condition pushdown (ICP). Several of the queries in sysbench have a WHERE condition that the optimizer uses for executing these queries as range scans. The upper and lower limit of the range scan will ensure that the WHERE condition is fulfilled. Still, the WHERE condition is part of the queries' condition and if ICP is enabled the condition will be pushed down to InnoDB as an index condition. Due to the range scan's upper and lower limits ensure that the WHERE condition is fulfilled, the pushed index condition will not filter out any records. As a result the use of ICP for these queries results in a performance overhead for sysbench. This overhead comes from using resources for determining the part of the condition that can be pushed down to InnoDB and overhead in InnoDB for executing the pushed index condition. With the default configuration for sysbench the range scans will use the primary key. This is a clustered index in InnoDB. Using ICP on a clustered index provides the lowest performance benefit since the entire record is part of the clustered index and in InnoDB it has the highest relative overhead for executing the pushed index condition. The fix for removing the overhead ICP introduces when running sysbench is to disable use of ICP when the index used by the query is a clustered index. When WL#6061 is implemented this change should be re-evaluated.
151 lines
6.3 KiB
Text
151 lines
6.3 KiB
Text
drop table if exists t0,t1,t2,t3;
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set @innodb_mrr_cpk_tmp=@@optimizer_switch;
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set optimizer_switch='mrr=on,mrr_sort_keys=on,index_condition_pushdown=on';
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set @save_join_cache_level=@@join_cache_level;
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set join_cache_level=6;
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set @save_storage_engine=@@storage_engine;
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set storage_engine=innodb;
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create table t0(a int);
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insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
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create table t1(a char(8), b char(8), filler char(100), primary key(a));
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show create table t1;
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Table Create Table
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t1 CREATE TABLE `t1` (
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`a` char(8) NOT NULL DEFAULT '',
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`b` char(8) DEFAULT NULL,
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`filler` char(100) DEFAULT NULL,
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PRIMARY KEY (`a`)
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) ENGINE=InnoDB DEFAULT CHARSET=latin1
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insert into t1 select
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concat('a-', 1000 + A.a + B.a*10 + C.a*100, '=A'),
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concat('b-', 1000 + A.a + B.a*10 + C.a*100, '=B'),
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'filler'
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from t0 A, t0 B, t0 C;
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create table t2 (a char(8));
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insert into t2 values ('a-1010=A'), ('a-1030=A'), ('a-1020=A');
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This should use join buffer:
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explain select * from t1, t2 where t1.a=t2.a;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t2 ALL NULL NULL NULL NULL 3 Using where
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1 SIMPLE t1 eq_ref PRIMARY PRIMARY 8 test.t2.a 1 Using join buffer (flat, BKA join); Key-ordered scan
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This output must be sorted by value of t1.a:
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select * from t1, t2 where t1.a=t2.a;
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a b filler a
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a-1010=A b-1010=B filler a-1010=A
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a-1020=A b-1020=B filler a-1020=A
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a-1030=A b-1030=B filler a-1030=A
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drop table t1, t2;
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create table t1(
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a char(8) character set utf8, b int, filler char(100),
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primary key(a,b)
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);
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insert into t1 select
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concat('a-', 1000 + A.a + B.a*10 + C.a*100, '=A'),
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1000 + A.a + B.a*10 + C.a*100,
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'filler'
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from t0 A, t0 B, t0 C;
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create table t2 (a char(8) character set utf8, b int);
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insert into t2 values ('a-1010=A', 1010), ('a-1030=A', 1030), ('a-1020=A', 1020);
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explain select * from t1, t2 where t1.a=t2.a and t1.b=t2.b;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t2 ALL NULL NULL NULL NULL 3 Using where
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1 SIMPLE t1 eq_ref PRIMARY PRIMARY 28 test.t2.a,test.t2.b 1 Using join buffer (flat, BKA join); Key-ordered scan
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select * from t1, t2 where t1.a=t2.a and t1.b=t2.b;
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a b filler a b
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a-1010=A 1010 filler a-1010=A 1010
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a-1020=A 1020 filler a-1020=A 1020
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a-1030=A 1030 filler a-1030=A 1030
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insert into t2 values ('a-1030=A', 1030), ('a-1020=A', 1020);
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explain select * from t1, t2 where t1.a=t2.a and t1.b=t2.b;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t2 ALL NULL NULL NULL NULL 5 Using where
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1 SIMPLE t1 eq_ref PRIMARY PRIMARY 28 test.t2.a,test.t2.b 1 Using join buffer (flat, BKA join); Key-ordered scan
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select * from t1, t2 where t1.a=t2.a and t1.b=t2.b;
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a b filler a b
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a-1010=A 1010 filler a-1010=A 1010
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a-1020=A 1020 filler a-1020=A 1020
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a-1020=A 1020 filler a-1020=A 1020
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a-1030=A 1030 filler a-1030=A 1030
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a-1030=A 1030 filler a-1030=A 1030
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drop table t1, t2;
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create table t1(
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a varchar(8) character set utf8, b int, filler char(100),
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primary key(a,b)
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);
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insert into t1 select
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concat('a-', 1000 + A.a + B.a*10 + C.a*100, '=A'),
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1000 + A.a + B.a*10 + C.a*100,
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'filler'
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from t0 A, t0 B, t0 C;
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create table t2 (a char(8) character set utf8, b int);
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insert into t2 values ('a-1010=A', 1010), ('a-1030=A', 1030), ('a-1020=A', 1020);
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explain select * from t1, t2 where t1.a=t2.a and t1.b=t2.b;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t2 ALL NULL NULL NULL NULL 3 Using where
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1 SIMPLE t1 eq_ref PRIMARY PRIMARY 30 test.t2.a,test.t2.b 1 Using where; Using join buffer (flat, BKA join); Key-ordered scan
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select * from t1, t2 where t1.a=t2.a and t1.b=t2.b;
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a b filler a b
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a-1010=A 1010 filler a-1010=A 1010
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a-1020=A 1020 filler a-1020=A 1020
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a-1030=A 1030 filler a-1030=A 1030
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explain select * from t1, t2 where t1.a=t2.a;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t2 ALL NULL NULL NULL NULL 3 Using where
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1 SIMPLE t1 ref PRIMARY PRIMARY 26 test.t2.a 1 Using where; Using join buffer (flat, BKA join); Key-ordered scan
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select * from t1, t2 where t1.a=t2.a;
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a b filler a b
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a-1010=A 1010 filler a-1010=A 1010
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a-1020=A 1020 filler a-1020=A 1020
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a-1030=A 1030 filler a-1030=A 1030
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drop table t1, t2;
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create table t1 (a int, b int, c int, filler char(100), primary key(a,b,c));
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insert into t1 select A.a, B.a, C.a, 'filler' from t0 A, t0 B, t0 C;
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insert into t1 values (11, 11, 11, 'filler');
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insert into t1 values (11, 11, 12, 'filler');
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insert into t1 values (11, 11, 13, 'filler');
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insert into t1 values (11, 22, 1234, 'filler');
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insert into t1 values (11, 33, 124, 'filler');
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insert into t1 values (11, 33, 125, 'filler');
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create table t2 (a int, b int);
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insert into t2 values (11,33), (11,22), (11,11);
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explain select * from t1, t2 where t1.a=t2.a and t1.b=t2.b;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t2 ALL NULL NULL NULL NULL 3 Using where
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1 SIMPLE t1 ref PRIMARY PRIMARY 8 test.t2.a,test.t2.b 1 Using join buffer (flat, BKA join); Key-ordered scan
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select * from t1, t2 where t1.a=t2.a and t1.b=t2.b;
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a b c filler a b
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11 11 11 filler 11 11
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11 11 12 filler 11 11
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11 11 13 filler 11 11
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11 22 1234 filler 11 22
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11 33 124 filler 11 33
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11 33 125 filler 11 33
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set join_cache_level=0;
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select * from t1, t2 where t1.a=t2.a and t1.b=t2.b;
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a b c filler a b
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11 33 124 filler 11 33
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11 33 125 filler 11 33
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11 22 1234 filler 11 22
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11 11 11 filler 11 11
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11 11 12 filler 11 11
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11 11 13 filler 11 11
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set join_cache_level=6;
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explain select * from t1, t2 where t1.a=t2.a and t2.b + t1.b > 100;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t2 ALL NULL NULL NULL NULL 3 Using where
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1 SIMPLE t1 ref PRIMARY PRIMARY 4 test.t2.a 1 Using where; Using join buffer (flat, BKA join); Key-ordered scan
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select * from t1, t2 where t1.a=t2.a and t2.b + t1.b > 100;
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a b c filler a b
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set optimizer_switch='index_condition_pushdown=off';
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explain select * from t1, t2 where t1.a=t2.a and t2.b + t1.b > 100;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t2 ALL NULL NULL NULL NULL 3 Using where
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1 SIMPLE t1 ref PRIMARY PRIMARY 4 test.t2.a 1 Using where; Using join buffer (flat, BKA join); Key-ordered scan
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select * from t1, t2 where t1.a=t2.a and t2.b + t1.b > 100;
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a b c filler a b
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set optimizer_switch='index_condition_pushdown=on';
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drop table t1,t2;
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set @@join_cache_level= @save_join_cache_level;
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set storage_engine=@save_storage_engine;
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set optimizer_switch=@innodb_mrr_cpk_tmp;
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drop table t0;
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