Commit 25c2d1ad authored by unknown's avatar unknown
Browse files

select_found.result, select_found.test: 

  Added a test case for bug #7945.
sql_select.cc:
  Fixed bug #7945. If DISTINCT is used only with constants
  in a query with GROUP BY, we can apply an optimization
  that set LIMIT to 1 only in the case when there is 
  no SQL_CALC_FOUND_ROWS.


sql/sql_select.cc:
  Fixed bug #7945. If DISTINCT is used only with constants
  in a query with GROUP BY, we can apply an optimization
  that set LIMIT to 1 only in the case when there is 
  no SQL_CALC_FOUND_ROWS.
mysql-test/t/select_found.test:
  Added a test case for bug #7945.
mysql-test/r/select_found.result:
  Added a test case for bug #7945.
parent 89a24f93

mysql-test/r/select_found.result

+8 −0
Original line number Diff line number Diff line
@@ -223,3 +223,11 @@ SELECT FOUND_ROWS(); 
FOUND_ROWS()

0

DROP TABLE t1;

CREATE TABLE t1 (a int, b int);

INSERT INTO t1 VALUES (1,2), (1,3), (1,4), (1,5);

SELECT SQL_CALC_FOUND_ROWS DISTINCT 'a' FROM t1 GROUP BY b LIMIT 2;

a

a

SELECT FOUND_ROWS();

FOUND_ROWS()

1

mysql-test/t/select_found.test

+9 −0
Original line number Diff line number Diff line
@@ -146,3 +146,12 @@ INSERT INTO t1 VALUES (0), (0), (1), (2); 
SELECT SQL_CALC_FOUND_ROWS * FROM t1 WHERE a = 0 GROUP BY a HAVING a > 10;

SELECT FOUND_ROWS();

DROP TABLE t1;



#

# Bug #7945: group by + distinct with constant expression + limit 

#



CREATE TABLE t1 (a int, b int);

INSERT INTO t1 VALUES (1,2), (1,3), (1,4), (1,5);

SELECT SQL_CALC_FOUND_ROWS DISTINCT 'a' FROM t1 GROUP BY b LIMIT 2;

SELECT FOUND_ROWS();

sql/sql_select.cc

+10 −3
Original line number Diff line number Diff line
@@ -2114,9 +2114,15 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count, 
		    x = used key parts (1 <= x <= c)

		  */

		  double rec_per_key;

#if 0

		  if (!(rec_per_key=(double)

			keyinfo->rec_per_key[keyinfo->key_parts-1]))

		    rec_per_key=(double) s->records/rec+1;

#else

                  rec_per_key= keyinfo->rec_per_key[keyinfo->key_parts-1] ?

		    (double) keyinfo->rec_per_key[keyinfo->key_parts-1] :

		    (double) s->records/rec+1;   

#endif



		  if (!s->records)

		    tmp=0;
@@ -6276,13 +6282,14 @@ remove_duplicates(JOIN *join, TABLE *entry,List<Item> &fields, Item *having) 
      field_count++;

  }



  if (!field_count)

  {						// only const items

  if (!field_count && !(join->select_options & OPTION_FOUND_ROWS)) 

  {                    // only const items with no OPTION_FOUND_ROWS

    join->thd->select_limit=1;	// Only send first row

    DBUG_RETURN(0);

  }

  Field **first_field=entry->field+entry->fields - field_count;

  offset=entry->field[entry->fields - field_count]->offset();

  offset= field_count ? 

          entry->field[entry->fields - field_count]->offset() : 0;

  reclength=entry->reclength-offset;



  free_io_cache(entry);				// Safety