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Fix for BUG#21787: COUNT(*) + ORDER BY + LIMIT returns wrong result

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The problem was due to a prior fix for BUG 9676, which limited
the rows stored in a temporary table to the LIMIT clause. This
optimization is not applicable to non-group queries with aggregate
functions. The fix disables the optimization in this case.


mysql-test/r/limit.result:
  Test case for BUG#21787
mysql-test/t/limit.test:
  Test case for BUG#21787
sql/sql_select.cc:
  If there is an aggregate function in a non-group query,
  materialize all rows in the temporary table no matter if
  there is a LIMIT clause. This is necessary, since the
  aggregate functions must be computed over all result rows,
  not just the first LIMIT rows.
This commit is contained in:
unknown
2006-09-01 15:07:04 +03:00
parent bfdbb780c2
commit b017caefbd
3 changed files with 38 additions and 5 deletions
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14
mysql-test/r/limit.result
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@ -76,3 +76,17 @@ a
a
1
drop table t1;
create table t1 (a int);
insert into t1 values (1),(2),(3),(4),(5),(6),(7);
explain select count(*) c FROM t1 WHERE a > 0 ORDER BY c LIMIT 3;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 7 Using where; Using temporary
select count(*) c FROM t1 WHERE a > 0 ORDER BY c LIMIT 3;
c
7
explain select sum(a) c FROM t1 WHERE a > 0 ORDER BY c LIMIT 3;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 7 Using where; Using temporary
select sum(a) c FROM t1 WHERE a > 0 ORDER BY c LIMIT 3;
c
28