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MDEV-17020: Assertion `length > 0' failed in ptr_compare upon ORDER BY with bad conversion

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This assert is hit when we do filesort using the priority queue and try to insert elements in
the queue. The compare function used for the priority queue should handle the case for zerolength
sortkey.
This commit is contained in:
Varun Gupta 2018-10-14 10:30:23 -07:00
parent 34f8a4071e
commit 3c5f6aa21c
3 changed files with 40 additions and 0 deletions
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20
mysql-test/r/order_by_zerolength-4285.result
View File

@ -24,3 +24,23 @@ Warning 1292 Truncated incorrect CHAR(0) value: '8'
Warning 1292 Truncated incorrect CHAR(0) value: '9'
Warning 1292 Truncated incorrect CHAR(0) value: '10'
drop table t1;
#
# MDEV-17020: Assertion `length > 0' failed in ptr_compare upon ORDER BY with bad conversion
#
set @save_sql_mode= @@sql_mode;
SET @@sql_mode= '';
CREATE TABLE t1 (pk INT PRIMARY KEY);
INSERT INTO t1 VALUES (1),(2);
explain
SELECT * FROM t1 ORDER BY 'foo', CONVERT(pk, CHAR(0)) LIMIT 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL PRIMARY 4 NULL 2 Using index; Using filesort
SELECT * FROM t1 ORDER BY 'foo', Cast(pk as CHAR(0)) LIMIT 2;
pk
1
2
Warnings:
Warning 1292 Truncated incorrect CHAR(0) value: '1'
Warning 1292 Truncated incorrect CHAR(0) value: '2'
set @@sql_mode= @save_sql_mode;
drop table t1;

13
mysql-test/t/order_by_zerolength-4285.test
View File

@ -6,3 +6,16 @@ insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
select * from t1 order by now(), cast(pk as char(0));
drop table t1;
--echo #
--echo # MDEV-17020: Assertion `length > 0' failed in ptr_compare upon ORDER BY with bad conversion
--echo #
set @save_sql_mode= @@sql_mode;
SET @@sql_mode= '';
CREATE TABLE t1 (pk INT PRIMARY KEY);
INSERT INTO t1 VALUES (1),(2);
explain
SELECT * FROM t1 ORDER BY 'foo', CONVERT(pk, CHAR(0)) LIMIT 2;
SELECT * FROM t1 ORDER BY 'foo', Cast(pk as CHAR(0)) LIMIT 2;
set @@sql_mode= @save_sql_mode;
drop table t1;

7
mysys/ptr_cmp.c
View File

@ -52,6 +52,11 @@ static int ptr_compare_0(size_t *compare_length, uchar **a, uchar **b);
static int ptr_compare_1(size_t *compare_length, uchar **a, uchar **b);
static int ptr_compare_2(size_t *compare_length, uchar **a, uchar **b);
static int ptr_compare_3(size_t *compare_length, uchar **a, uchar **b);
static int degenerate_compare_func(size_t *compare_length, uchar **a, uchar **b)
{
DBUG_ASSERT(*compare_length == 0);
return 0;
}
#endif /* __sun */
/* Get a pointer to a optimal byte-compare function for a given size */
@ -64,6 +69,8 @@ qsort2_cmp get_ptr_compare (size_t size __attribute__((unused)))
#else
qsort2_cmp get_ptr_compare (size_t size)
{
if (size == 0)
return (qsort2_cmp) degenerate_compare_func;
if (size < 4)
return (qsort2_cmp) ptr_compare;
switch (size & 3) {