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Fix for bug #34512: CAST( AVG( double ) AS DECIMAL )

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returns wrong results

Casting AVG() to DECIMAL led to incorrect results when the arguments
had a non-DECIMAL type, because in this case
Item_sum_avg::val_decimal() performed the division by the number of
arguments twice.

Fixed by changing Item_sum_avg::val_decimal() to not rely on
Item_sum_sum::val_decimal(), i.e. calculate sum and divide using
DECIMAL arithmetics for DECIMAL arguments, and utilize val_real() with
subsequent conversion to DECIMAL otherwise.


mysql-test/r/func_group.result:
  Added a test case for bug #34512.
mysql-test/t/func_group.test:
  Added a test case for bug #34512.
sql/item_sum.cc:
  Do not use Item_sum_sum::val_decimal() in Item_sum_avg::val_decimal()
  because the first one, depending on the arguments type, may return
  either the sum of the arguments, or the average calculated by the
  virtual val_real() method of Item_sum_avg. Instead, do our own
  calculation based on the arguments type.
This commit is contained in:
unknown
2008-03-06 18:19:47 +03:00
parent 64bdb0bdf2
commit 8270d9875f
3 changed files with 25 additions and 1 deletions
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6
mysql-test/r/func_group.result
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@ -1419,4 +1419,10 @@ Note 1003 select (`test`.`t1`.`a` + 1) AS `y` from `test`.`t1` group by (`test`.
DROP VIEW v1;
DROP TABLE t1;
SET SQL_MODE=DEFAULT;
CREATE TABLE t1(a DOUBLE);
INSERT INTO t1 VALUES (10), (20);
SELECT AVG(a), CAST(AVG(a) AS DECIMAL) FROM t1;
AVG(a) CAST(AVG(a) AS DECIMAL)
15 15
DROP TABLE t1;
End of 5.0 tests