mariadb/mysql-test/t/show_explain.test

#
# Tests for SHOW EXPLAIN FOR functionality
#
--source include/have_debug.inc

--disable_warnings
drop table if exists t0, t1, t2, t3, t4;
drop view if exists v1;
--enable_warnings

# 
# Testcases in this file do not work with embedded server. The reason for this
# is that we use the following commands for synchronization:
#
#    set @show_explain_probe_select_id=1;
#    set debug_dbug='d,show_explain_probe_join_exec_start';
#    send select count(*) from t1 where a < 100000;
#
# When ran with mysqltest_embedded, this translates into: 
#
#    Thread1> DBUG_PUSH("d,show_explain_probe_join_exec_start");
#    Thread1> create another thread for doing "send ... reap"
#    Thread2> mysql_parse("select count(*) from t1 where a < 100000");
#
# That is, "select count(*) ..." is ran in a thread for which DBUG_PUSH(...)
# has not been called. As a result, show_explain_probe_join_exec_start does not fire, and
# "select count(*) ..." does not wait till its SHOW EXPLAIN command, and the
# test fails.
#
-- source include/not_embedded.inc


create table t0 (a int);
insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table t1 (a int);
insert into t1 select A.a + 10*B.a + 100*C.a from t0 A, t0 B, t0 C;
alter table t1 add b int, add c int, add filler char(32);
update t1 set b=a, c=a, filler='fooo';
alter table t1 add key(a), add key(b);

# 
# Try killing a non-existent thread
# 
--error ER_NO_SUCH_THREAD
show explain for 2*1000*1000*1000;

--error ER_NOT_SUPPORTED_YET
show explain for (select max(a) from t0);

# 
# Setup two threads and their ids
#
let $thr1=`select connection_id()`;
connect (con1, localhost, root,,);
connection con1;
let $thr2=`select connection_id()`;
connection default;

# SHOW EXPLAIN FOR <idle thread>
--error ER_ERROR_WHEN_EXECUTING_COMMAND
evalp show explain for $thr2;

# SHOW EXPLAIN FOR <ourselves>
--error ER_ERROR_WHEN_EXECUTING_COMMAND
evalp show explain for $thr1;

let $wait_condition= select State='show_explain_trap' from information_schema.processlist where id=$thr2;

#
# Test SHOW EXPLAIN for simple queries
#
connection con1;
set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_join_exec_start';
send select count(*) from t1 where a < 100000;

connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;


send select max(c) from t1 where a < 10;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;


--echo # We can catch EXPLAIN, too.
set @show_expl_tmp= @@optimizer_switch;
set optimizer_switch='index_condition_pushdown=on,mrr=on,mrr_sort_keys=on';
send explain select max(c) from t1 where a < 10;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;
set optimizer_switch= @show_expl_tmp;


--echo # UNION, first branch 
set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_join_exec_start';
send explain select a from t0 A union select a+1 from t0 B;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;


--echo # UNION, second branch
set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_join_exec_start';
send explain select a from t0 A union select a+1 from t0 B;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;


--echo # Uncorrelated  subquery, select
set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_join_exec_start';
send select a, (select max(a) from t0 B) from t0 A where a<1;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;


--echo # Uncorrelated  subquery, explain
set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_join_exec_start';
send explain select a, (select max(a) from t0 B) from t0 A where a<1;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;

--echo # correlated  subquery, select
set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_join_exec_start';
send select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;

--echo # correlated  subquery, explain
set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_join_exec_start';
send select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;

--echo # correlated  subquery, select, while inside the subquery
set @show_explain_probe_select_id=2; # <---
set debug_dbug='d,show_explain_probe_join_exec_start';
send select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;

--echo # correlated  subquery, explain, while inside the subquery
set @show_explain_probe_select_id=2;
set debug_dbug='d,show_explain_probe_join_exec_start';
send select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;


--echo # correlated  subquery, explain, while inside the subquery
set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_join_exec_end';
send select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1;
connection default;
--source include/wait_condition.inc
--error ER_ERROR_WHEN_EXECUTING_COMMAND
evalp show explain for $thr2;
connection con1;
reap;

# TODO: explain in the parent subuqery when the un-correlated child has been
# run (and have done irreversible cleanups)
#  ^^ Is this at all possible after 5.3? 
#     Maybe, for 5.3 try this: 
#       - run before/after the parent has invoked child's optimization
#       - run after materialization 

--echo # Try to do SHOW EXPLAIN for a query that runs a  SET command:
--echo #   I've found experimentally that select_id==2 here...
--echo # 
set @show_explain_probe_select_id=2;
set debug_dbug='d,show_explain_probe_join_exec_start';
send set @foo= (select max(a) from t0 where sin(a) >0);
connection default;
--source include/wait_condition.inc
--error ER_ERROR_WHEN_EXECUTING_COMMAND
evalp show explain for $thr2;
connection con1;
reap;

--echo #
--echo # Attempt SHOW EXPLAIN for an UPDATE
--echo #
create table t2 as select a as a, a as dummy from t0 limit 2;
set @show_explain_probe_select_id=2;
set debug_dbug='d,show_explain_probe_join_exec_start';
send update t2 set dummy=0 where (select max(a) from t0 where t2.a + t0.a <3) >3 ;
connection default;
--source include/wait_condition.inc
--error ER_ERROR_WHEN_EXECUTING_COMMAND
evalp show explain for $thr2;
--error ER_ERROR_WHEN_EXECUTING_COMMAND
evalp show explain for $thr2;
connection con1;
reap;
drop table t2;

--echo #
--echo # Attempt SHOW EXPLAIN for a DELETE
--echo # 
create table t2 as select a as a, a as dummy from t0 limit 2;
set @show_explain_probe_select_id=2;
set debug_dbug='d,show_explain_probe_join_exec_start';
send delete from t2 where (select max(a) from t0 where t2.a + t0.a <3) >3 ;
connection default;
--source include/wait_condition.inc
--error ER_ERROR_WHEN_EXECUTING_COMMAND
evalp show explain for $thr2;
--error ER_ERROR_WHEN_EXECUTING_COMMAND
evalp show explain for $thr2;
connection con1;
reap;
drop table t2;


--echo #
--echo # Multiple SHOW EXPLAIN calls for one select 
--echo # 
create table t2 as select a as a, a as dummy from t0 limit 3;
set @show_explain_probe_select_id=2;
set debug_dbug='d,show_explain_probe_join_exec_start';
send select t2.a, ((select max(a) from t0 where t2.a + t0.a <3) >3) as SUBQ from t2;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
evalp show explain for $thr2;
evalp show explain for $thr2;
connection con1;
reap;
drop table t2;

--echo #
--echo # SHOW EXPLAIN for SELECT ... ORDER BY with "Using filesort"
--echo #
explain select * from t0 order by a;

set debug_dbug='d,show_explain_probe_join_exec_start';
set @show_explain_probe_select_id=1;
send select * from t0 order by a; 
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;

--echo #
--echo # SHOW EXPLAIN for SELECT ... with "Using temporary"
--echo #
connection default;
explain select distinct a from t0;
connection con1;

set debug_dbug='d,show_explain_probe_join_exec_start';
set @show_explain_probe_select_id=1;
send select distinct a from t0; 
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;

--echo #
--echo # SHOW EXPLAIN for SELECT ... with "Using temporary; Using filesort"
--echo #
connection default;
explain select distinct a from t0;
connection con1;

set debug_dbug='d,show_explain_probe_join_exec_start';
set @show_explain_probe_select_id=1;
send select distinct a from t0; 
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;
set debug_dbug='';

--echo #
--echo # MDEV-238: SHOW EXPLAIN: Server crashes in JOIN::print_explain with FROM subquery and GROUP BY
--echo #
CREATE TABLE t2 ( a INT ); 
INSERT INTO t2 VALUES (1),(2),(1),(4),(2);
explain SELECT alias.a FROM t2, ( SELECT * FROM t2 ) AS alias GROUP BY alias.a;

set debug_dbug='d,show_explain_in_find_all_keys';
send SELECT alias.a FROM t2, ( SELECT * FROM t2 ) AS alias GROUP BY alias.a;

connection default;
--source include/wait_condition.inc
--echo # FIXED by "conservative assumptions about when QEP is available" fix:
--echo #    NOTE: current code will not show "Using join buffer": 
--error ER_ERROR_WHEN_EXECUTING_COMMAND
evalp show explain for $thr2;
connection con1;
reap;
set debug_dbug='';
DROP TABLE t2;


--echo #
--echo # MDEV-239: Assertion `field_types == 0 ... ' failed in Protocol_text::store(double, uint32, String*) with 
--echo #          SHOW EXPLAIN over EXPLAIN EXTENDED
--echo #


CREATE TABLE t2 (a INT); 
INSERT INTO t2 VALUES (1),(2),(1),(4),(2);

EXPLAIN EXTENDED SELECT alias.a FROM t2, ( SELECT * FROM t2 ) AS alias GROUP BY alias.a ;

set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_join_exec_end';
send EXPLAIN EXTENDED SELECT alias.a FROM t2, ( SELECT * FROM t2 ) AS alias GROUP BY alias.a ;

connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;
set debug_dbug='';
DROP TABLE t2;


--echo #
--echo # MDEV-240: SHOW EXPLAIN: Assertion `this->optimized == 2' failed in 
--echo # JOIN::print_explain on query with a JOIN, TEMPTABLE view,
--echo #          
CREATE TABLE t3 (a INT); 
CREATE ALGORITHM=TEMPTABLE VIEW v1 AS SELECT * FROM t3;
INSERT INTO t3 VALUES (8);
CREATE TABLE t2 (b INT);
INSERT INTO t2 VALUES (4),(5),(6),(7),(8),(9);
explain SELECT * FROM v1, t2;

set @show_explain_probe_select_id=2;
set debug_dbug='d,show_explain_probe_join_exec_end';
send SELECT * FROM v1, t2;

connection default;
--source include/wait_condition.inc
--error ER_ERROR_WHEN_EXECUTING_COMMAND
evalp show explain for $thr2;
connection con1;
reap;
set debug_dbug='';
DROP VIEW v1;
DROP TABLE t2, t3;

--echo #
--echo # MDEV-267: SHOW EXPLAIN: Server crashes in JOIN::print_explain on most of queries
--echo #
set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_join_exec_end';
send select sleep(1);
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;
set debug_dbug='';


--echo #
--echo # Same as above, but try another reason for JOIN to be degenerate
--echo #
set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_join_exec_end';
send select * from t0 where 1>10;
connection default;
--source include/wait_condition.inc
--error ER_ERROR_WHEN_EXECUTING_COMMAND
evalp show explain for $thr2;
connection con1;
reap;
set debug_dbug='';

--echo #
--echo # Same as above, but try another reason for JOIN to be degenerate (2)
--echo #
create table t3(a int primary key);
insert into t3 select a from t0;
set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_join_exec_end';
send select * from t0,t3 where t3.a=112233;
connection default;
--source include/wait_condition.inc
--error ER_ERROR_WHEN_EXECUTING_COMMAND
evalp show explain for $thr2;
connection con1;
reap;
set debug_dbug='';
drop table t3;

--echo #
--echo # MDEV-270: SHOW EXPLAIN: server crashes in JOIN::print_explain on a query with 
--echo #           select tables optimized away
--echo #

CREATE TABLE t2 (pk INT PRIMARY KEY, a INT ) ENGINE=MyISAM; 
INSERT INTO t2 VALUES 
  (1,4),(2,62),(3,7),(4,1),(5,0),(6,7),(7,7),(8,1),(9,7),(10,1),
  (11,5),(12,2),(13,0),(14,1),(15,8),(16,1),(17,1),(18,9),(19,1),(20,5) ;

explain SELECT * FROM t2 WHERE a = 
       (SELECT MAX(a) FROM t2 
        WHERE pk= (SELECT MAX(pk) FROM t2 WHERE pk = 3)
       );

set @show_explain_probe_select_id=2;
set debug_dbug='d,show_explain_probe_do_select';
send SELECT * FROM t2 WHERE a = 
       (SELECT MAX(a) FROM t2 
        WHERE pk= (SELECT MAX(pk) FROM t2 WHERE pk = 3)
       );
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;
set debug_dbug='';
drop table t2;


--echo #
--echo # MDEV-273: SHOW EXPLAIN: server crashes in JOIN::print_explain on a query with impossible WHERE
--echo #
CREATE TABLE t2 (a1 INT, KEY(a1)) ENGINE=MyISAM;
INSERT INTO t2 VALUES
  (4),(6),(7),(1),(0),(7),(7),(1),(7),(1),
  (5),(2),(0),(1),(8),(1),(1),(9),(1),(5);

CREATE TABLE t3 (b1 INT) ENGINE=MyISAM;
INSERT INTO t3 VALUES
  (4),(5),(8),(4),(8),(2),(9),(6),(4),(8),
  (3),(5),(9),(6),(8),(3),(2),(6),(3),(1),
  (4),(3),(1),(7),(0),(0),(9),(5),(9),(0),
  (2),(2),(5),(9),(1),(4),(8),(6),(5),(5),
  (1),(7),(2),(8),(9),(3),(2),(6),(6),(5),
  (4),(3),(2),(7),(4),(6),(0),(8),(5),(8),
  (2),(9),(7),(5),(7),(0),(4),(3),(1),(0),
  (6),(2),(8),(3),(7),(3),(5),(5),(1),(2),
  (1),(7),(1),(9),(9),(8),(3);
CREATE TABLE t4 (c1 INT) ENGINE=MyISAM;

EXPLAIN
SELECT count(*) FROM t2, t3
WHERE a1 < ALL ( 
  SELECT a1 FROM t2
  WHERE a1 IN ( SELECT a1 FROM t2, t4 )
);

set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_do_select';
send
SELECT count(*) FROM t2, t3
WHERE a1 < ALL ( 
  SELECT a1 FROM t2
  WHERE a1 IN ( SELECT a1 FROM t2, t4 )
);

connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;
set debug_dbug='';
drop table t2, t3, t4;

--echo #
--echo # MDEV-275: SHOW EXPLAIN: server crashes in JOIN::print_explain with IN subquery and aggregate function
--echo #
CREATE TABLE t2 ( `pk` INT NOT NULL PRIMARY KEY, `a1` INT NOT NULL, KEY(`a1`)) ENGINE=MyISAM; 
INSERT INTO t2 VALUES 
  (1,5),(2,4),(3,6),(4,9),(5,2),(6,8),(7,4),(8,8),(9,0),(10,43),
  (11,23),(12,3),(13,45),(14,16),(15,2),(16,33),(17,2),(18,5),(19,9),(20,2);

set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_join_exec_end';
send
  SELECT * FROM t2 WHERE (5, 78) IN (SELECT `a1`, MAX(`a1`) FROM t2 GROUP BY `a1`);
connection default;
--source include/wait_condition.inc
--error ER_ERROR_WHEN_EXECUTING_COMMAND
evalp show explain for $thr2;
connection con1;
reap;
set debug_dbug='';

DROP TABLE t2;

DROP TABLE t1;

--echo #
--echo # MDEV-305: SHOW EXPLAIN: ref returned by SHOW EXPLAIN is different from the normal EXPLAIN ('const' vs empty string)
--echo #
CREATE TABLE t1(a INT, KEY(a));
INSERT INTO t1 VALUES (3),(1),(5),(1);

set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_join_exec_start';

send SELECT 'test' FROM t1 WHERE a=1;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;
set debug_dbug='';

DROP TABLE t1;


--echo #
--echo # MDEV-299: SHOW EXPLAIN: Plan produced by SHOW EXPLAIN changes back and forth during query execution
--echo #

create table t1 (key1 int, col1 int, col2 int, filler char(100), key(key1));
insert into t1 select A.a+ 10 * B.a, 10, 10, 'filler-data' from t0 A, t0 B;

# Make matches 3 records 
update t1 set col1=3, col2=10 where key1=1; # small range
update t1 set col1=3, col2=1000 where key1=2; # big range 
update t1 set col1=3, col2=10 where key1=3; # small range again
update t1 set col1=3, col2=1000 where key1=4; # big range 

set @tmp_mdev299_jcl= @@join_cache_level;
set join_cache_level=0;

explain select count(*) from t1 A, t1 B where B.key1 < A.col2 and A.col1=3 AND B.col2 + 1 < 100;

set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_test_if_quick_select';

send 
select count(*) from t1 A, t1 B where B.key1 < A.col2 and A.col1=3 AND B.col2 + 1 < 100;

connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
--source include/wait_condition.inc
evalp show explain for $thr2;
--source include/wait_condition.inc
evalp show explain for $thr2;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;

set debug_dbug='';
drop table t1;

--echo #
--echo # MDEV-297: SHOW EXPLAIN: Server gets stuck until timeout occurs while
--echo #           executing SHOW INDEX and SHOW EXPLAIN in parallel
--echo #
CREATE TABLE t1(a INT, b INT, c INT, KEY(a), KEY(b), KEY(c));
INSERT INTO t1 (a) VALUES (3),(1),(5),(1);

set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_join_exec_start';

send SHOW INDEX FROM t1;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;
set debug_dbug='';

DROP TABLE t1;

--echo #
--echo # MDEV-324: SHOW EXPLAIN: Plan produced by SHOW EXPLAIN for a query with TEMPTABLE view 
--echo #           loses 'DERIVED' line on the way without saying that the plan was already deleted
--echo #
CREATE TABLE t1 (a INT);
INSERT INTO t1 VALUES (1),(2);
CREATE ALGORITHM=TEMPTABLE VIEW v1 AS SELECT * FROM t1;

EXPLAIN SELECT a + 1 FROM v1;

set debug_dbug='d,show_explain_probe_join_tab_preread';
set @show_explain_probe_select_id=1;

send
  SELECT a + 1 FROM v1;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;
set debug_dbug='';

DROP VIEW v1;
DROP TABLE t1;


--echo #
--echo # MDEV-323: SHOW EXPLAIN: Plan produced by SHOW EXPLAIN loses 
--echo #            'UNION RESULT' line on the way without saying that the plan was already deleted
--echo #
CREATE TABLE t1 (a INT);
INSERT INTO t1 VALUES (4),(6);

EXPLAIN 
SELECT a FROM t1 WHERE a IN ( SELECT 1+SLEEP(0.01) UNION SELECT 2 );

set debug_dbug='d,show_explain_probe_union_read';
send
SELECT a FROM t1 WHERE a IN ( SELECT 1+SLEEP(0.01) UNION SELECT 2 );

connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;

--source include/wait_condition.inc
evalp show explain for $thr2;

connection con1;
reap;

set debug_dbug='';

DROP TABLE t1;

--echo #
--echo # MDEV-327: SHOW EXPLAIN: Different select_type in plans produced by SHOW EXPLAIN 
--echo #           and standard EXPLAIN: 'SUBQUERY' vs 'DEPENDENT SUBQUERY'
--echo #
CREATE TABLE t1 (a INT) ENGINE=Aria;
INSERT INTO t1 VALUES
(4),(6),(3),(5),(3),(246),(2),(9),(3),(8),
(1),(8),(8),(5),(7),(5),(1),(6),(2),(9);

CREATE TABLE t2 (b INT) ENGINE=Aria;
INSERT INTO t2 VALUES
(1),(7),(4),(7),(0),(2),(9),(4),(0),(9),
(1),(3),(8),(8),(18),(84),(6),(3),(6),(6);

EXPLAIN
SELECT * FROM t1, ( SELECT * FROM t2 ) AS alias
WHERE a < ALL ( SELECT b FROM t1, t2 WHERE a = b );

set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_join_exec_start';
--send
SELECT * FROM t1, ( SELECT * FROM t2 ) AS alias
WHERE a < ALL ( SELECT b FROM t1, t2 WHERE a = b );

connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;

connection con1;
reap;
set debug_dbug='';
DROP TABLE t1, t2;

--echo # 
--echo #  Test that SHOW EXPLAIN will print 'Distinct'.
--echo #
CREATE TABLE t1 (a int(10) unsigned not null primary key,b int(10) unsigned);
INSERT INTO t1 VALUES (1,1),(2,1),(3,1),(4,1);

CREATE TABLE t3 (a int(10) unsigned, key(A), b text);
INSERT INTO t3 VALUES (1,'1'),(2,'2');

create temporary table t4 select * from t3;
insert into t3 select * from t4;
insert into t4 select * from t3;
insert into t3 select * from t4;
insert into t4 select * from t3;
insert into t3 select * from t4;
insert into t4 select * from t3;
insert into t3 select * from t4;
explain select distinct t1.a from t1,t3 where t1.a=t3.a;

set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_join_exec_start';
--send
select distinct t1.a from t1,t3 where t1.a=t3.a;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;

connection con1;
reap;
set debug_dbug='';

drop table t1,t3,t4;
## TODO: Test this: have several SHOW EXPLAIN requests be queued up for a
##       thread and served together.

## TODO: SHOW EXPLAIN while the primary query is running EXPLAIN EXTENDED/PARTITIONS
##

drop table t0;