BUG#19684: Garbage in 'partitions' column in EXPLAIN output:

In select_describe(), make the String object that holds the value of 
"partitions" column to "own" the value buffer, so the buffer isn't
prematurely freed.
[this is the second attempt with review fixes]


mysql-test/r/partition_pruning.result:
  BUG#19684: Testcase
mysql-test/t/partition_pruning.test:
  BUG#19684: Testcase
sql/sql_select.cc:
  BUG#19684: Garbage in 'partitions' column in EXPLAIN output:
  - Added comment
  - Make the String object that holds the value of "partitions" column
    to "own" the value buffer, so the buffer isn't prematurely freed.

1 files changed, 19 insertions, 0 deletions

diff --git a/mysql-test/r/partition_pruning.result b/mysql-test/r/partition_pruning.result
index 62c7a962ba1..950a83c6d4f 100644
--- a/mysql-test/r/partition_pruning.result
+++ b/mysql-test/r/partition_pruning.result
@@ -678,3 +678,22 @@ explain partitions select * from t1 where s1 = 0 or s1 is null;
 id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	p0	ALL	NULL	NULL	NULL	NULL	3	Using where
 drop table t1;
+create table t2 (a int, b int)
+partition by LIST(a)
+subpartition by HASH(b) subpartitions 40
+( partition p_0_long_partition_name values in(1),
+partition p_1_long_partition_name values in(2));
+insert into t2 values (1,1),(2,2);
+explain partitions select * from t2;
+id	1
+select_type	SIMPLE
+table	t2
+partitions	p_0_long_partition_name_p_0_long_partition_namesp0,p_0_long_partition_name_p_0_long_partition_namesp1,p_0_long_partition_name_p_0_long_partition_namesp2,p_0_long_partition_name_p_0_long_partition_namesp3,p_0_long_partition_name_p_0_long_partition_namesp4,p_0_long_partition_name_p_0_long_partition_namesp5,p_0_long_partition_name_p_0_long_partition_namesp6,p_0_long_partition_name_p_0_long_partition_namesp7,p_0_long_partition_name_p_0_long_partition_namesp8,p_0_long_partition_name_p_0_long_partition_namesp9,p_0_long_partition_name_p_0_long_partition_namesp10,p_0_long_partition_name_p_0_long_partition_namesp11,p_0_long_partition_name_p_0_long_partition_namesp12,p_0_long_partition_name_p_0_long_partition_namesp13,p_0_long_partition_name_p_0_long_partition_namesp14,p_0_long_partition_name_p_0_long_partition_namesp15,p_0_long_partition_name_p_0_long_partition_namesp16,p_0_long_partition_name_p_0_long_partition_namesp17,p_0_long_partition_name_p_0_long_partition_namesp18,p_0_long_partition_name_p_0_long_partition_namesp19,p_0_long_partition_name_p_0_long_partition_namesp20,p_0_long_partition_name_p_0_long_partition_namesp21,p_0_long_partition_name_p_0_long_partition_namesp22,p_0_long_partition_name_p_0_long_partition_namesp23,p_0_long_partition_name_p_0_long_partition_namesp24,p_0_long_partition_name_p_0_long_partition_namesp25,p_0_long_partition_name_p_0_long_partition_namesp26,p_0_long_partition_name_p_0_long_partition_namesp27,p_0_long_partition_name_p_0_long_partition_namesp28,p_0_long_partition_name_p_0_long_partition_namesp29,p_0_long_partition_name_p_0_long_partition_namesp30,p_0_long_partition_name_p_0_long_partition_namesp31,p_0_long_partition_name_p_0_long_partition_namesp32,p_0_long_partition_name_p_0_long_partition_namesp33,p_0_long_partition_name_p_0_long_partition_namesp34,p_0_long_partition_name_p_0_long_partition_namesp35,p_0_long_partition_name_p_0_long_partition_namesp36,p_0_long_partition_name_p_0_long_partition_namesp37,p_0_long_partition_name_p_0_long_partition_namesp38,p_0_long_partition_name_p_0_long_partition_namesp39,p_1_long_partition_name_p_1_long_partition_namesp0,p_1_long_partition_name_p_1_long_partition_namesp1,p_1_long_partition_name_p_1_long_partition_namesp2,p_1_long_partition_name_p_1_long_partition_namesp3,p_1_long_partition_name_p_1_long_partition_namesp4,p_1_long_partition_name_p_1_long_partition_namesp5,p_1_long_partition_name_p_1_long_partition_namesp6,p_1_long_partition_name_p_1_long_partition_namesp7,p_1_long_partition_name_p_1_long_partition_namesp8,p_1_long_partition_name_p_1_long_partition_namesp9,p_1_long_partition_name_p_1_long_partition_namesp10,p_1_long_partition_name_p_1_long_partition_namesp11,p_1_long_partition_name_p_1_long_partition_namesp12,p_1_long_partition_name_p_1_long_partition_namesp13,p_1_long_partition_name_p_1_long_partition_namesp14,p_1_long_partition_name_p_1_long_partition_namesp15,p_1_long_partition_name_p_1_long_partition_namesp16,p_1_long_partition_name_p_1_long_partition_namesp17,p_1_long_partition_name_p_1_long_partition_namesp18,p_1_long_partition_name_p_1_long_partition_namesp19,p_1_long_partition_name_p_1_long_partition_namesp20,p_1_long_partition_name_p_1_long_partition_namesp21,p_1_long_partition_name_p_1_long_partition_namesp22,p_1_long_partition_name_p_1_long_partition_namesp23,p_1_long_partition_name_p_1_long_partition_namesp24,p_1_long_partition_name_p_1_long_partition_namesp25,p_1_long_partition_name_p_1_long_partition_namesp26,p_1_long_partition_name_p_1_long_partition_namesp27,p_1_long_partition_name_p_1_long_partition_namesp28,p_1_long_partition_name_p_1_long_partition_namesp29,p_1_long_partition_name_p_1_long_partition_namesp30,p_1_long_partition_name_p_1_long_partition_namesp31,p_1_long_partition_name_p_1_long_partition_namesp32,p_1_long_partition_name_p_1_long_partition_namesp33,p_1_long_partition_name_p_1_long_partition_namesp34,p_1_long_partition_name_p_1_long_partition_namesp35,p_1_long_partition_name_p_1_long_partition_namesp36,p_1_long_partition_name_p_1_long_partition_namesp37,p_1_long_partition_name_p_1_long_partition_namesp38,p_1_long_partition_name_p_1_long_partition_namesp39
+type	ALL
+possible_keys	NULL
+key	NULL
+key_len	NULL
+ref	NULL
+rows	2
+Extra	
+drop table t2;