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MDEV-270: SHOW EXPLAIN: server crashes in JOIN::print_explain on a query with

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select tables optimized away
- Take into account, that for some degenerate joins instead of "join->table_count=0"
  the code sets "join->tables_list=0".
This commit is contained in:
Sergey Petrunya
2012-05-15 15:56:50 +04:00
parent b3841ae9e4
commit 382e81ca84
4 changed files with 83 additions and 1 deletions
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39
mysql-test/r/show_explain.result
View File

@@ -414,4 +414,43 @@ Note 1003 select * from t0,t3 where t3.a=112233
a a
set debug='';
drop table t3;
#
# MDEV-270: SHOW EXPLAIN: server crashes in JOIN::print_explain on a query with
# select tables optimized away
#
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)
);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t2 ALL NULL NULL NULL NULL 20 Using where
2 SUBQUERY t2 const PRIMARY PRIMARY 4 const 1 Using where
3 SUBQUERY NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
set @show_explain_probe_select_id=2;
set debug='d,show_explain_probe_do_select';
SELECT * FROM t2 WHERE a =
(SELECT MAX(a) FROM t2
WHERE pk= (SELECT MAX(pk) FROM t2 WHERE pk = 3)
);
show explain for $thr2;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t2 ALL NULL NULL NULL NULL 20 Using where
2 SUBQUERY t2 const PRIMARY PRIMARY 4 1 Using where
3 SUBQUERY NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
Warnings:
Note 1003 SELECT * FROM t2 WHERE a =
(SELECT MAX(a) FROM t2
WHERE pk= (SELECT MAX(pk) FROM t2 WHERE pk = 3)
)
pk a
3 7
6 7
7 7
9 7
set debug='';
drop table t2;
drop table t0,t1;

34
mysql-test/t/show_explain.test
View File

@@ -414,6 +414,40 @@ reap;
set debug='';
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='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='';
drop table t2;
## TODO: Test this: have several SHOW EXPLAIN requests be queued up for a
## thread and served together.

2
sql/sql_lex.cc
View File

@@ -3752,7 +3752,7 @@ int st_select_lex::print_explain(select_result_sink *output,
int res;
if (join && join->optimized == JOIN::OPTIMIZATION_DONE)
{
if (!join->table_count)
if (!join->table_count || !join->tables_list)
{
/* It's a degenerate join */
const char *cause= join->zero_result_cause ? join-> zero_result_cause :

9
sql/sql_select.cc
View File

@@ -15399,6 +15399,15 @@ do_select(JOIN *join,List<Item> *fields,TABLE *table,Procedure *procedure)
else
{
DBUG_ASSERT(join->table_count);
THD *thd= join->thd;
DBUG_EXECUTE_IF("show_explain_probe_do_select",
if (dbug_user_var_equals_int(thd,
"show_explain_probe_select_id",
join->select_lex->select_number))
dbug_serve_apcs(thd, 1);
);
if (join->outer_ref_cond && !join->outer_ref_cond->val_int())
error= NESTED_LOOP_NO_MORE_ROWS;
else