答复: TOPN value, which sum measure column group by dimension, error.

[苏 志锋]

I change the measure column "V" data type from integer to double. resubmit the 
sqls.
SQL:   SELECT LV1,SUM(V) V FROM TEST GROUP BY LV1
Return:             LV1       V
                         001      -0.994

whithe sum(v) value should be -1.0, but kylin return -0.994.
dd
SQL:  SELECT LV1,SUM(V) V,COUNT(*) C FROM TEST GROUP BY LV1
Return:              LV1       V        C
                          001       -1.0     1
the sum(v) is right.
________________________________
发件人: 苏 志锋 <roc...@live.com>
发送时间: 2017年5月15日 12:06:41
收件人: user@kylin.apache.org
主题: TOPN value, which sum measure column group by dimension, error.


TOPN value, which sum measure column group by dimension, error.

Environment

         Apache Kylin:1.6.0

STEPS

  1.  Kafka produce one message
  2.  kylin consume the message
  3.  kylin build cuboid
  4.  execute sql

KafKa JSON data

         {“T”:”2017-05-15”,“LV1”:”001”,”V”:-1}

MODEL

         1、Dimensions : T, LV1

         2、Measures : V

CUBE

  1.  Dimensions : T, LV1
  2.  Measures: _COUNT_; SUM(V); TOPN SUM COLUMN V GROUP BY LV1;

SQL and result

1、  SELECT LV1,SUM(V) V FROM TEST GROUP BY LV1

LV1


V


001


0




2、  SELECT LV1,SUM(V) V,COUNT(*) C FROM TEST GROUP BY LV1

LV1


V


C


001


-1


1


Problem

        The sum(v) value is error in sql 1, and correct in sql 2.

The probably reasons are:

1、org.apache.kylin.measure.topn. TopNCounterSerializer.deserialize function 
deserialize -1 to -0.99.

2、org.apache.kylin.metadata.tuple.setMeasureValue function convert 
double(-0.99) to long(0)