MWL#182: Explain running statements: merge with 5.3-main (needs fixing)

2 files changed, 326 insertions, 0 deletions

diff --git a/mysql-test/r/show_explain.result b/mysql-test/r/show_explain.result
new file mode 100644
index 00000000000..b8b732f9607
--- /dev/null
+++ b/mysql-test/r/show_explain.result
@@ -0,0 +1,128 @@
+drop table if exists t0, t1;
+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);
+show explain for 2*1000*1000*1000;
+ERROR HY000: Unknown thread id: 2000000000
+show explain for (select max(a) from t0);
+ERROR 42000: This version of MySQL doesn't yet support 'Usage of subqueries or stored function calls as part of this statement'
+show explain for $thr2;
+ERROR HY000: Error when executing command SHOW EXPLAIN: Target is not running EXPLAINable command
+show explain for $thr1;
+ERROR HY000: Error when executing command SHOW EXPLAIN: Target is not running EXPLAINable command
+set @show_explain_probe_select_id=1;
+set debug='d,show_explain_probe_1';
+select count(*) from t1 where a < 100000;
+show explain for $thr2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index	a	a	5	NULL	1000	Using where; Using index
+count(*)
+1000
+select max(c) from t1 where a < 10;
+show explain for $thr2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	a	a	5	NULL	10	Using where
+max(c)
+9
+# We can catch EXPLAIN, too.
+set @show_expl_tmp= @@optimizer_switch;
+set optimizer_switch='index_condition_pushdown=on,mrr=on,mrr_sort_keys=on';
+explain select max(c) from t1 where a < 10;
+show explain for $thr2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	a	a	5	NULL	10	Using index condition; Rowid-ordered scan
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	a	a	5	NULL	10	Using index condition; Rowid-ordered scan
+set optimizer_switch= @show_expl_tmp;
+# UNION, first branch 
+set @show_explain_probe_select_id=1;
+set debug='d,show_explain_probe_1';
+explain select a from t0 A union select a+1 from t0 B;
+show explain for $thr2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	A	ALL	NULL	NULL	NULL	NULL	10	
+2	UNION	B	ALL	NULL	NULL	NULL	NULL	10	
+NULL	UNION RESULT	<union1,2>	ALL	NULL	NULL	NULL	NULL	NULL	
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	A	ALL	NULL	NULL	NULL	NULL	10	
+2	UNION	B	ALL	NULL	NULL	NULL	NULL	10	
+NULL	UNION RESULT	<union1,2>	ALL	NULL	NULL	NULL	NULL	NULL	
+# UNION, second branch
+set @show_explain_probe_select_id=1;
+set debug='d,show_explain_probe_1';
+explain select a from t0 A union select a+1 from t0 B;
+show explain for $thr2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	A	ALL	NULL	NULL	NULL	NULL	10	
+2	UNION	B	ALL	NULL	NULL	NULL	NULL	10	
+NULL	UNION RESULT	<union1,2>	ALL	NULL	NULL	NULL	NULL	NULL	
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	A	ALL	NULL	NULL	NULL	NULL	10	
+2	UNION	B	ALL	NULL	NULL	NULL	NULL	10	
+NULL	UNION RESULT	<union1,2>	ALL	NULL	NULL	NULL	NULL	NULL	
+# Uncorrelated  subquery, select
+set @show_explain_probe_select_id=1;
+set debug='d,show_explain_probe_1';
+select a, (select max(a) from t0 B) from t0 A where a<1;
+show explain for $thr2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	A	ALL	NULL	NULL	NULL	NULL	10	Using where
+2	SUBQUERY	B	ALL	NULL	NULL	NULL	NULL	10	
+a	(select max(a) from t0 B)
+0	9
+# Uncorrelated  subquery, explain
+set @show_explain_probe_select_id=1;
+set debug='d,show_explain_probe_1';
+explain select a, (select max(a) from t0 B) from t0 A where a<1;
+show explain for $thr2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	A	ALL	NULL	NULL	NULL	NULL	10	Using where
+2	SUBQUERY	B	ALL	NULL	NULL	NULL	NULL	10	
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	A	ALL	NULL	NULL	NULL	NULL	10	Using where
+2	SUBQUERY	B	ALL	NULL	NULL	NULL	NULL	10	
+# correlated  subquery, select
+set @show_explain_probe_select_id=1;
+set debug='d,show_explain_probe_1';
+select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1;
+show explain for $thr2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	a	ALL	NULL	NULL	NULL	NULL	10	Using where
+2	DEPENDENT SUBQUERY	b	ALL	NULL	NULL	NULL	NULL	10	Using where
+a	(select max(a) from t0 b where b.a+a.a<10)
+0	9
+# correlated  subquery, explain
+set @show_explain_probe_select_id=1;
+set debug='d,show_explain_probe_1';
+select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1;
+show explain for $thr2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	a	ALL	NULL	NULL	NULL	NULL	10	Using where
+2	DEPENDENT SUBQUERY	b	ALL	NULL	NULL	NULL	NULL	10	Using where
+a	(select max(a) from t0 b where b.a+a.a<10)
+0	9
+# correlated  subquery, select, while inside the subquery
+set @show_explain_probe_select_id=2;
+set debug='d,show_explain_probe_1';
+select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1;
+show explain for $thr2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	a	ALL	NULL	NULL	NULL	NULL	10	Using where
+2	DEPENDENT SUBQUERY	b	ALL	NULL	NULL	NULL	NULL	10	Using where
+a	(select max(a) from t0 b where b.a+a.a<10)
+0	9
+# correlated  subquery, explain, while inside the subquery
+set @show_explain_probe_select_id=2;
+set debug='d,show_explain_probe_1';
+select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1;
+show explain for $thr2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	a	ALL	NULL	NULL	NULL	NULL	10	Using where
+2	DEPENDENT SUBQUERY	b	ALL	NULL	NULL	NULL	NULL	10	Using where
+a	(select max(a) from t0 b where b.a+a.a<10)
+0	9
+drop table t0,t1;
diff --git a/mysql-test/t/show_explain.test b/mysql-test/t/show_explain.test
new file mode 100644
index 00000000000..5ed78be1ea4
--- /dev/null
+++ b/mysql-test/t/show_explain.test
@@ -0,0 +1,198 @@
+#
+# Tests for SHOW EXPLAIN FOR functionality
+#
+--source include/have_debug.inc
+
+--disable_warnings
+drop table if exists t0, t1;
+--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='d,show_explain_probe_1';
+#    send select count(*) from t1 where a < 100000;
+#
+# When ran with mysqltest_embedded, this translates into: 
+#
+#    Thread1> DBUG_PUSH("d,show_explain_probe_1");
+#    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_1 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='d,show_explain_probe_1';
+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='d,show_explain_probe_1';
+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='d,show_explain_probe_1';
+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='d,show_explain_probe_1';
+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='d,show_explain_probe_1';
+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='d,show_explain_probe_1';
+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='d,show_explain_probe_1';
+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='d,show_explain_probe_1';
+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='d,show_explain_probe_1';
+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;
+
+
+# TODO: explain in the parent subuqery when the un-correlated child has been
+# run (and have done irreversible cleanups)
+
+# TODO: hit JOIN::optimize for non-select commands: UPDATE/DELETE, SET.
+
+
+## TODO: Test this: multiple SHOW EXPLAIN calls in course of running of one select
+## 
+## TODO: Test this: have several SHOW EXPLAIN requests be queued up for a
+##       thread and served together.
+
+drop table t0,t1;