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select_found.result, select_found.test:

Browse source 
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.
This commit is contained in:
igor@rurik.mysql.com 2005-01-22 02:40:27 -08:00
parent 3215550735
commit 8527f256c0
3 changed files with 27 additions and 3 deletions
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8
mysql-test/r/select_found.result
View file

@ -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

9
mysql-test/t/select_found.test
View file

@ -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();

13
sql/sql_select.cc
View file

@ -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