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be8709eb7b
This task involves the implementation for the optimizer trace.
This feature produces a trace for any SELECT/UPDATE/DELETE/,
which contains information about decisions taken by the optimizer during
the optimization phase (choice of table access method, various costs,
transformations, etc). This feature would help to tell why some decisions were
taken by the optimizer and why some were rejected.
Trace is session-local, controlled by the @@optimizer_trace variable.
To enable optimizer trace we need to write:
set @@optimizer_trace variable= 'enabled=on';
To display the trace one can run:
SELECT trace FROM INFORMATION_SCHEMA.OPTIMIZER_TRACE;
This task also involves:
MDEV-18489: Limit the memory used by the optimizer trace
introduces a switch optimizer_trace_max_mem_size which limits
the memory used by the optimizer trace. This was implemented by
Sergei Petrunia.
336 lines
9.3 KiB
Plaintext
336 lines
9.3 KiB
Plaintext
--source include/not_embedded.inc
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SELECT table_name, column_name FROM information_schema.columns where table_name="OPTIMIZER_TRACE";
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show variables like 'optimizer_trace';
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set optimizer_trace="enabled=on";
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show variables like 'optimizer_trace';
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set optimizer_trace="enabled=off";
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create table t1 (a int, b int);
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insert into t1 values (1,2),(2,3);
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create table t2 (b int);
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insert into t2 values (1),(2);
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analyze table t1;
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analyze table t2;
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create function f1 (a int) returns INT
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return 1;
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create view v1 as select * from t1 where t1.a=1;
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create view v2 as select * from t1 where t1.a=1 group by t1.b;
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set optimizer_trace="enabled=on";
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--echo # Mergeable views/derived tables
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select * from v1;
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select * from information_schema.OPTIMIZER_TRACE;
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select * from (select * from t1 where t1.a=1)q;
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select * from information_schema.OPTIMIZER_TRACE;
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--echo # Non-Mergeable views
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select * from v2;
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select * from information_schema.OPTIMIZER_TRACE;
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drop table t1,t2;
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drop view v1,v2;
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drop function f1;
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create table t1(a int, b int);
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insert into t1 values (0,0),(1,1),(2,1),(3,2),(4,3),
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(5,3),(6,3),(7,3),(8,3),(9,3);
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create table t2(a int, b int);
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insert into t2 values (0,0),(1,1),(2,1),(3,2),(4,3),
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(5,3),(6,3),(7,3),(8,3),(9,3);
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ANALYZE TABLE t1;
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ANALYZE TABLE t2;
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create view v1 as select a from t1 group by b;
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create view v2 as select a from t2;
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--echo # Mergeable view
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explain select * from v2 ;
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select * from information_schema.OPTIMIZER_TRACE;
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--echo # Non-Mergeable view
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explain select * from v1 ;
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select * from information_schema.OPTIMIZER_TRACE;
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drop table t1,t2;
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drop view v1,v2;
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--echo #
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--echo # print ref-keyues array
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--echo #
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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 int, b int, c int, key(a));
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insert into t1 select A.a*10 + B.a, A.a*10 + B.a, A.a*10 + B.a from t0 A, t0 B;
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create table t2(a int, b int, c int , key(a));
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insert into t2 select A.a*10 + B.a, A.a*10 + B.a, A.a*10 + B.a from t0 A, t0 B;
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analyze table t1;
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analyze table t2;
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explain select * from t1,t2 where t1.a=t2.b+2 and t2.a= t1.b;
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select * from information_schema.OPTIMIZER_TRACE;
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drop table t1,t2,t0;
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--echo #
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--echo # group_by min max optimization
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--echo #
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CREATE TABLE t1 (id INT NOT NULL AUTO_INCREMENT PRIMARY KEY, a INT NOT NULL, KEY(a));
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--disable_query_log
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INSERT INTO t1(a) VALUES (1), (2), (3), (4);
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INSERT INTO t1(a) SELECT a FROM t1;
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INSERT INTO t1(a) SELECT a FROM t1;
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INSERT INTO t1(a) SELECT a FROM t1;
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INSERT INTO t1(a) SELECT a FROM t1;
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INSERT INTO t1(a) SELECT a FROM t1;
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INSERT INTO t1(a) SELECT a FROM t1;
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INSERT INTO t1(a) SELECT a FROM t1;
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INSERT INTO t1(a) SELECT a FROM t1;
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INSERT INTO t1(a) SELECT a FROM t1;
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INSERT INTO t1(a) SELECT a FROM t1;
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INSERT INTO t1(a) SELECT a FROM t1;
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INSERT INTO t1(a) SELECT a FROM t1;
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INSERT INTO t1(a) SELECT a FROM t1;
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INSERT INTO t1(a) SELECT a FROM t1;
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--enable_query_log
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analyze table t1;
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EXPLAIN SELECT DISTINCT a FROM t1;
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select * from information_schema.OPTIMIZER_TRACE;
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drop table t1;
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--echo #
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--echo # With group by , where clause and MIN/MAX function
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--echo #
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CREATE TABLE t1 (a INT, b INT, c int, d int, KEY(a,b,c,d));
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INSERT INTO t1 VALUES (1,1,1,1), (2,2,2,2), (3,3,3,3), (4,4,4,4), (1,0,1,1), (3,2,3,3), (4,5,4,4);
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ANALYZE TABLE t1;
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EXPLAIN SELECT MIN(d) FROM t1 where b=2 and c=3 group by a;
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select * from information_schema.OPTIMIZER_TRACE;
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DROP TABLE t1;
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CREATE TABLE t1 (id INT NOT NULL, a DATE, KEY(id,a));
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INSERT INTO t1 values (1,'2001-01-01'),(1,'2001-01-02'),
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(1,'2001-01-03'),(1,'2001-01-04'),
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(2,'2001-01-01'),(2,'2001-01-02'),
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(2,'2001-01-03'),(2,'2001-01-04'),
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(3,'2001-01-01'),(3,'2001-01-02'),
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(3,'2001-01-03'),(3,'2001-01-04'),
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(4,'2001-01-01'),(4,'2001-01-02'),
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(4,'2001-01-03'),(4,'2001-01-04');
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set optimizer_trace='enabled=on';
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EXPLAIN SELECT id,MIN(a),MAX(a) FROM t1 WHERE a>=20010104e0 GROUP BY id;
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select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
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EXPLAIN SELECT * FROM t1 WHERE a = 20010104e0 GROUP BY id;
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select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
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drop table t1;
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--echo #
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--echo # Late ORDER BY optimization
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--echo #
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create table ten(a int);
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insert into ten values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
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create table one_k(a int primary key);
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insert into one_k select A.a + B.a* 10 + C.a * 100 from ten A, ten B, ten C;
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create table t1 (
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pk int not null,
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a int,
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b int,
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c int,
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filler char(100),
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KEY a_a(c),
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KEY a_c(a,c),
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KEY a_b(a,b)
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);
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insert into t1
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select a, a,a,a, 'filler-dataaa' from test.one_k;
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update t1 set a=1 where pk between 0 and 180;
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update t1 set b=2 where pk between 0 and 20;
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analyze table t1;
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set optimizer_trace='enabled=on';
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explain select * from t1 where a=1 and b=2 order by c limit 1;
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select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
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drop table t1,ten,one_k;
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--echo #
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--echo # TABLE ELIMINATION
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--echo #
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create table t1 (a int);
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insert into t1 values (0),(1),(2),(3);
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create table t0 as select * from t1;
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create table t2 (a int primary key, b int)
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as select a, a as b from t1 where a in (1,2);
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create table t3 (a int primary key, b int)
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as select a, a as b from t1 where a in (1,3);
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set optimizer_trace='enabled=on';
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analyze table t1;
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analyze table t2;
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analyze table t3;
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--echo # table t2 should be eliminated
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explain
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select t1.a from t1 left join t2 on t1.a=t2.a;
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select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
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--echo # no tables should be eliminated
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explain select * from t1 left join t2 on t2.a=t1.a;
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select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
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--echo # multiple tables are eliminated
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explain select t1.a from t1 left join (t2 join t3 on t2.b=t3.b) on t2.a=t1.a and t3.a=t1.a;
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select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
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drop table t0, t1, t2, t3;
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--echo #
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--echo # IN subquery to sem-join is traced
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--echo #
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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 int, b int);
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insert into t1 values (0,0),(1,1),(2,2);
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create table t2 as select * from t1;
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create table t11(a int, b int);
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create table t10 (pk int, a int);
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insert into t10 select a,a from t0;
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create table t12 like t10;
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insert into t12 select * from t10;
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analyze table t1,t10;
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set optimizer_trace='enabled=on';
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explain extended select * from t1 where a in (select pk from t10);
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select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
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drop table t0,t1,t11,t10,t12,t2;
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--echo #
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--echo # Selectivities for columns and indexes.
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--echo #
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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 (
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pk int,
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a int,
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b int,
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key pk(pk),
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key pk_a(pk,a),
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key pk_a_b(pk,a,b));
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insert into t1 select a,a,a from t0;
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ANALYZE TABLE t1 PERSISTENT FOR COLUMNS (a,b) INDEXES ();
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set @save_optimizer_use_condition_selectivity=@@optimizer_use_condition_selectivity;
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set @save_use_stat_tables= @@use_stat_tables;
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set @@optimizer_use_condition_selectivity=4;
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set @@use_stat_tables= PREFERABLY;
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set optimizer_trace='enabled=on';
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explain select * from t1 where pk = 2 and a=5 and b=1;
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select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
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set @@optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
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set @@use_stat_tables= @save_use_stat_tables;
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drop table t0,t1;
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set optimizer_trace="enabled=off";
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--echo #
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--echo # Tests added to show that sub-statements are not traced
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--echo #
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create table t1(a int);
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insert into t1 values (1),(2),(3),(4);
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create table t2(a int);
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insert into t2 values (1),(2),(3),(4);
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delimiter |;
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create function f1(a int) returns int
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begin
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declare a int default 0;
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set a= a+ (select count(*) from t2);
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return a;
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end|
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create function f2(a int) returns int
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begin
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declare a int default 0;
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select count(*) from t2 into a;
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return a;
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end|
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delimiter ;|
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set optimizer_trace='enabled=on';
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select f1(a) from t1;
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select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
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select f2(a) from t1;
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select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
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drop table t1,t2;
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drop function f1;
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drop function f2;
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set optimizer_trace='enabled=off';
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--echo #
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--echo # MDEV-18489: Limit the memory used by the optimizer trace
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--echo #
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create table t1 (a int);
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insert into t1 values (1),(2);
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set optimizer_trace='enabled=on';
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set @save_optimizer_trace_max_mem_size= @@optimizer_trace_max_mem_size;
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select * from t1;
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select length(trace) from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
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set optimizer_trace_max_mem_size=100;
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select * from t1;
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select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
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set optimizer_trace_max_mem_size=0;
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select * from t1;
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select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
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drop table t1;
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set optimizer_trace='enabled=off';
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set @@optimizer_trace_max_mem_size= @save_optimizer_trace_max_mem_size;
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--echo #
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--echo # MDEV-18527: Optimizer trace for DELETE query shows table:null
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--echo #
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create table ten(a int);
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insert into ten values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
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create table t0 (a int, b int);
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insert into t0 select a,a from ten;
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alter table t0 add key(a);
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set optimizer_trace=1;
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explain delete from t0 where t0.a<3;
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select * from information_schema.optimizer_trace;
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drop table ten,t0;
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set optimizer_trace='enabled=off';
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--echo #
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--echo # MDEV-18528: Optimizer trace support for multi-table UPDATE and DELETE
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--echo #
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create table ten(a int);
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insert into ten values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
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create table t0 (a int, b int);
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insert into t0 select a,a from ten;
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alter table t0 add key(a);
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create table t1 like t0;
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insert into t1 select * from t0;
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explain delete t0,t1 from t0, t1 where t0.a=t1.a and t1.a<3;
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select * from information_schema.optimizer_trace;
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drop table ten,t0,t1;
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