[jira] [Created] (HIVE-5878) Hive standard avg UDAF returns double as the return type for some exact input types

["Xuefu Zhang (JIRA)" <ji...@apache.org>]

Xuefu Zhang created HIVE-5878:
---------------------------------

             Summary: Hive standard avg UDAF returns double as the return type for some exact input types
                 Key: HIVE-5878
                 URL: https://issues.apache.org/jira/browse/HIVE-5878
             Project: Hive
          Issue Type: Bug
          Components: Types, UDF
    Affects Versions: 0.12.0
            Reporter: Xuefu Zhang
            Assignee: Xuefu Zhang


For standard, no-partial avg result, hive currently returns double as the result type.
{code}
hive> desc test;
OK
d                   	int                 	None                
Time taken: 0.051 seconds, Fetched: 1 row(s)
hive> explain select avg(`d`) from test;  
...
      Reduce Operator Tree:
        Group By Operator
          aggregations:
                expr: avg(VALUE._col0)
          bucketGroup: false
          mode: mergepartial
          outputColumnNames: _col0
          Select Operator
            expressions:
                  expr: _col0
                  type: double
{code}
However, exact types including integers and decimal should yield exact type. Here is what MySQL does:
{code}
mysql> desc test;
+-------+--------------+------+-----+---------+-------+
| Field | Type         | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| i     | int(11)      | YES  |     | NULL    |       |
| b     | tinyint(1)   | YES  |     | NULL    |       |
| d     | double       | YES  |     | NULL    |       |
| s     | varchar(5)   | YES  |     | NULL    |       |
| dd    | decimal(5,2) | YES  |     | NULL    |       |
+-------+--------------+------+-----+---------+-------+
mysql> desc test62;
+-------+---------------+------+-----+---------+-------+
| Field | Type          | Null | Key | Default | Extra |
+-------+---------------+------+-----+---------+-------+
| sum_t | decimal(14,4) | YES  |     | NULL    |       |
+-------+---------------+------+-----+---------+-------+
1 row in set (0.00 sec)
{code}



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