Commit fd4c9af3 authored by Sergey Petrunya's avatar Sergey Petrunya

MDEV-6442: Assertion `join->best_read < double(...)' failed with...

MDEV-6442: Assertion `join->best_read < double(...)' failed with optimizer_use_condition_selectivity >=3

- Fix the crash by making get_column_range_cardinality() 
  to handle the special case where Column_stats objects 
  is an all-zeros object (the question of what is the point
  of having Field::read_stats point to such object remains a 
  mystery)

- Added a few comments. Learning the code still.
parent 689ffe35
......@@ -1358,6 +1358,8 @@ set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivit
DROP TABLE t1,t2;
set use_stat_tables=@save_use_stat_tables;
set optimizer_switch=@save_optimizer_switch_for_selectivity_test;
set @tmp_ust= @@use_stat_tables;
set @tmp_oucs= @@optimizer_use_condition_selectivity;
#
# MDEV-6808: MariaDB 10.0.13 crash with optimizer_use_condition_selectivity > 1
#
......@@ -1393,4 +1395,22 @@ t2.subject_type in ('user')
repost_id subject_type subject_id object_type object_id is_private event_id
DROP TABLE t1, t2;
set optimizer_use_condition_selectivity=@tmp_mdev6808;
#
# MDEV-6442: Assertion `join->best_read < double(...)' failed with optimizer_use_condition_selectivity >=3, ...
#
SET use_stat_tables = PREFERABLY;
SET optimizer_use_condition_selectivity = 3;
CREATE TABLE t1 ( a VARCHAR(3), b VARCHAR(8), KEY (a,b) ) ENGINE=InnoDB;
INSERT INTO t1 VALUES ('USA','Chinese'),('USA','English');
CREATE TABLE t2 (i INT) ENGINE=InnoDB;
SELECT * FROM t1, t2 WHERE ( 't', 'o' ) IN (
SELECT t1_2.b, t1_1.a FROM t1 AS t1_1 STRAIGHT_JOIN t1 AS t1_2 ON ( t1_2.a = t1_1.b )
);
a b i
DROP TABLE t1,t2;
#
# End of 10.0 tests
#
set use_stat_tables= @tmp_ust;
set optimizer_use_condition_selectivity= @tmp_oucs;
SET SESSION STORAGE_ENGINE=DEFAULT;
......@@ -8,6 +8,9 @@ set optimizer_switch='extended_keys=on';
--source selectivity.test
set optimizer_switch=@save_optimizer_switch_for_selectivity_test;
set @tmp_ust= @@use_stat_tables;
set @tmp_oucs= @@optimizer_use_condition_selectivity;
--echo #
--echo # MDEV-6808: MariaDB 10.0.13 crash with optimizer_use_condition_selectivity > 1
......@@ -46,4 +49,26 @@ WHERE
DROP TABLE t1, t2;
set optimizer_use_condition_selectivity=@tmp_mdev6808;
--echo #
--echo # MDEV-6442: Assertion `join->best_read < double(...)' failed with optimizer_use_condition_selectivity >=3, ...
--echo #
SET use_stat_tables = PREFERABLY;
SET optimizer_use_condition_selectivity = 3;
CREATE TABLE t1 ( a VARCHAR(3), b VARCHAR(8), KEY (a,b) ) ENGINE=InnoDB;
INSERT INTO t1 VALUES ('USA','Chinese'),('USA','English');
CREATE TABLE t2 (i INT) ENGINE=InnoDB;
SELECT * FROM t1, t2 WHERE ( 't', 'o' ) IN (
SELECT t1_2.b, t1_1.a FROM t1 AS t1_1 STRAIGHT_JOIN t1 AS t1_2 ON ( t1_2.a = t1_1.b )
);
DROP TABLE t1,t2;
--echo #
--echo # End of 10.0 tests
--echo #
set use_stat_tables= @tmp_ust;
set optimizer_use_condition_selectivity= @tmp_oucs;
SET SESSION STORAGE_ENGINE=DEFAULT;
......@@ -3502,7 +3502,7 @@ double get_column_range_cardinality(Field *field,
!(range_flag & NEAR_MIN);
if (col_non_nulls < 1)
res= 0;
res= 0; /* this is likely wrong, see MDEV-6843 */
else if (min_endp && max_endp && min_endp->length == max_endp->length &&
!memcmp(min_endp->key, max_endp->key, min_endp->length))
{
......@@ -3515,6 +3515,15 @@ double get_column_range_cardinality(Field *field,
{
double avg_frequency= col_stats->get_avg_frequency();
res= avg_frequency;
/*
psergey-todo: what does check for min_value, max_value mean?
min/max_value are set to NULL in alloc_statistics_for_table() and
alloc_statistics_for_table_share(). Both functions will immediately
call create_min_max_statistical_fields_for_table and
create_min_max_statistical_fields_for_table_share() respectively,
which will set min/max_value to be valid pointers, unless OOM
occurs.
*/
if (avg_frequency > 1.0 + 0.000001 &&
col_stats->min_value && col_stats->max_value)
{
......@@ -3530,6 +3539,11 @@ double get_column_range_cardinality(Field *field,
avg_frequency / col_non_nulls);
}
}
else if (avg_frequency == 0.0)
{
/* This actually means there is no statistics data */
res= tab_records;
}
}
}
else
......
......@@ -280,7 +280,14 @@ public:
};
/* Statistical data on a column */
/*
Statistical data on a column
Note: objects of this class may be "empty", where they have almost all fields
as zeros, for example, get_avg_frequency() will return 0.
objects are allocated in alloc_statistics_for_table[_share].
*/
class Column_statistics
{
......@@ -296,7 +303,8 @@ public:
are available for the column
*/
uint32 column_stat_nulls;
/* For the below two, see comments in get_column_range_cardinality() */
/* Minimum value for the column */
Field *min_value;
/* Maximum value for the column */
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment