Commit 8270d987 authored by unknown's avatar unknown

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

                    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.
parent 64bdb0bd
......@@ -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
......@@ -916,5 +916,15 @@ DROP VIEW v1;
DROP TABLE t1;
SET SQL_MODE=DEFAULT;
#
# Bug #34512: CAST( AVG( double ) AS DECIMAL ) returns wrong results
#
CREATE TABLE t1(a DOUBLE);
INSERT INTO t1 VALUES (10), (20);
SELECT AVG(a), CAST(AVG(a) AS DECIMAL) FROM t1;
DROP TABLE t1;
###
--echo End of 5.0 tests
......@@ -1206,7 +1206,15 @@ my_decimal *Item_sum_avg::val_decimal(my_decimal *val)
null_value=1;
return NULL;
}
sum_dec= Item_sum_sum::val_decimal(&sum_buff);
/*
For non-DECIMAL hybrid_type the division will be done in
Item_sum_avg::val_real().
*/
if (hybrid_type != DECIMAL_RESULT)
return val_decimal_from_real(val);
sum_dec= dec_buffs + curr_dec_buff;
int2my_decimal(E_DEC_FATAL_ERROR, count, 0, &cnt);
my_decimal_div(E_DEC_FATAL_ERROR, val, sum_dec, &cnt, prec_increment);
return val;
......
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