Commit decf9082 authored by unknown's avatar unknown
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Bug #22342: No results returned for query using max and group by 

 When using index for group by and range access the server isolates    
 a set of ranges based on the conditions over the key parts of the
 index used. Then it uses only the ranges over the GROUP BY fields to
 jump from one group to another. Since the GROUP BY fields may form a
 prefix over the index, we may use only a prefix of the ranges produced
 by the range optimizer.
 Each range contains a notion on whether it includes its border values.
 The problem is that when using a range prefix, the last range is open
 because it assumes that there is a range on the next keypart. Thus when
 we use a prefix range as it is, it excludes all border values.
 The solution is when ignoring the suffix of the range conditions 
 (to jump over the GROUP BY prefix only) the server must change the 
 remaining intervals so they always contain their borders, e.g. 
 if the whole range was :
 (1,-inf) <= (<group_by_col>,<min_max_arg_col>) < (1, 3) we must make
 (1) <= (<group_by_col>) <= (1) because (a,b) < (c1,c2) means :
 a < c1 OR (a = c1 AND b < c2).


mysql-test/r/group_min_max.result:
  Bug #22342: No results returned for query using max and group by
   - test case
mysql-test/t/group_min_max.test:
  Bug #22342: No results returned for query using max and group by
   - test case
sql/opt_range.cc:
  Bug #22342: No results returned for query using max and group by
   - open the intervals for prefix select when there are more conditions
     than used for the prefix search.
sql/opt_range.h:
  Bug #22342: No results returned for query using max and group by
   - open the intervals for prefix select when there are more conditions
     than used for the prefix search.
parent 54bb1045

mysql-test/r/group_min_max.result

+20 −0
Original line number Diff line number Diff line
@@ -2142,3 +2142,23 @@ t1; 
id2	id3	id5	id4	id3	id6	id5	id1

1	1	1	1	1	1	1	1

DROP TABLE t1,t2,t3,t4,t5,t6;

CREATE TABLE t1 (a int, b int, PRIMARY KEY (a,b), KEY b (b));

INSERT INTO t1 VALUES (1,1),(1,2);

explain SELECT MAX(b), a FROM t1 WHERE b < 2 AND a = 1 GROUP BY a;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	range	PRIMARY,b	PRIMARY	8	NULL	2	Using where; Using index for group-by

SELECT MAX(b), a FROM t1 WHERE b < 2 AND a = 1 GROUP BY a;

MAX(b)	a

1	1

SELECT MIN(b), a FROM t1 WHERE b > 1 AND a = 1 GROUP BY a;

MIN(b)	a

2	1

CREATE TABLE t2 (a int, b int, c int, PRIMARY KEY (a,b,c));

INSERT INTO t2 SELECT a,b,b FROM t1;

explain SELECT MIN(c) FROM t2 WHERE b = 2 and a = 1 and c > 1 GROUP BY a;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t2	range	PRIMARY	PRIMARY	12	NULL	2	Using where; Using index for group-by

SELECT MIN(c) FROM t2 WHERE b = 2 and a = 1 and c > 1 GROUP BY a;

MIN(c)

2

DROP TABLE t1,t2;

mysql-test/t/group_min_max.test

+16 −0
Original line number Diff line number Diff line
@@ -794,3 +794,19 @@ SELECT * FROM 
t1;



DROP TABLE t1,t2,t3,t4,t5,t6;



#

# Bug#22342: No results returned for query using max and group by

#

CREATE TABLE t1 (a int, b int, PRIMARY KEY (a,b), KEY b (b));

INSERT INTO t1 VALUES (1,1),(1,2);



explain SELECT MAX(b), a FROM t1 WHERE b < 2 AND a = 1 GROUP BY a;

SELECT MAX(b), a FROM t1 WHERE b < 2 AND a = 1 GROUP BY a;

SELECT MIN(b), a FROM t1 WHERE b > 1 AND a = 1 GROUP BY a;

CREATE TABLE t2 (a int, b int, c int, PRIMARY KEY (a,b,c));

INSERT INTO t2 SELECT a,b,b FROM t1;

explain SELECT MIN(c) FROM t2 WHERE b = 2 and a = 1 and c > 1 GROUP BY a;

SELECT MIN(c) FROM t2 WHERE b = 2 and a = 1 and c > 1 GROUP BY a;



DROP TABLE t1,t2;

sql/opt_range.cc

+37 −0
Original line number Diff line number Diff line
@@ -8374,6 +8374,7 @@ TRP_GROUP_MIN_MAX::make_quick(PARAM *param, bool retrieve_full_rows, 
    quick->quick_prefix_select= NULL;



  quick->update_key_stat();

  quick->adjust_prefix_ranges();



  DBUG_RETURN(quick);

}
@@ -8603,6 +8604,42 @@ bool QUICK_GROUP_MIN_MAX_SELECT::add_range(SEL_ARG *sel_range) 
}





/*

  Opens the ranges if there are more conditions in quick_prefix_select than

  the ones used for jumping through the prefixes.



  SYNOPSIS

    QUICK_GROUP_MIN_MAX_SELECT::adjust_prefix_ranges()



  NOTES

    quick_prefix_select is made over the conditions on the whole key.

    It defines a number of ranges of length x. 

    However when jumping through the prefixes we use only the the first 

    few most significant keyparts in the range key. However if there

    are more keyparts to follow the ones we are using we must make the 

    condition on the key inclusive (because x < "ab" means 

    x[0] < 'a' OR (x[0] == 'a' AND x[1] < 'b').

    To achive the above we must turn off the NEAR_MIN/NEAR_MAX

*/

void QUICK_GROUP_MIN_MAX_SELECT::adjust_prefix_ranges ()

{

  if (quick_prefix_select &&

      group_prefix_len < quick_prefix_select->max_used_key_length)

  {

    DYNAMIC_ARRAY *arr;

    uint inx;



    for (inx= 0, arr= &quick_prefix_select->ranges; inx < arr->elements; inx++)

    {

      QUICK_RANGE *range;



      get_dynamic(arr, (gptr)&range, inx);

      range->flag &= ~(NEAR_MIN | NEAR_MAX);

    }

  }

}





/*

  Determine the total number and length of the keys that will be used for

  index lookup.

sql/opt_range.h

+2 −0
Original line number Diff line number Diff line
@@ -294,6 +294,7 @@ class QUICK_RANGE_SELECT : public QUICK_SELECT_I 
  friend class QUICK_SELECT_DESC;

  friend class QUICK_INDEX_MERGE_SELECT;

  friend class QUICK_ROR_INTERSECT_SELECT;

  friend class QUICK_GROUP_MIN_MAX_SELECT;



  DYNAMIC_ARRAY ranges;     /* ordered array of range ptrs */

  QUICK_RANGE **cur_range;  /* current element in ranges  */
@@ -642,6 +643,7 @@ class QUICK_GROUP_MIN_MAX_SELECT : public QUICK_SELECT_I 
  ~QUICK_GROUP_MIN_MAX_SELECT();

  bool add_range(SEL_ARG *sel_range);

  void update_key_stat();

  void adjust_prefix_ranges();

  bool alloc_buffers();

  int init();

  int reset();