[jira] [Created] (KYLIN-3687) Top_N measure requires related SUM() measure to be defined as part of the cube to work, but Web UI allows creation of the cube that has Top_N measure only, resulting in NPE at query time

["Vsevolod Ostapenko (JIRA)" <ji...@apache.org>]

Vsevolod Ostapenko created KYLIN-3687:
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             Summary: Top_N measure requires related SUM() measure to be defined as part of the cube to work, but Web UI allows creation of the cube that has Top_N measure only, resulting in NPE at query time
                 Key: KYLIN-3687
                 URL: https://issues.apache.org/jira/browse/KYLIN-3687
             Project: Kylin
          Issue Type: Improvement
          Components: Measure - TopN, Metadata, Web 
    Affects Versions: v2.5.0
         Environment: HDP 2.5.6, Kylin 2.5
            Reporter: Vsevolod Ostapenko


Web UI allows defining a cube with Top_N measure without defining a related SUM() measure. E.g. a variation of the kylin_sales_cube can be successfully defined via UI with just TOP_SELLER without actually defining GVM_SUM measure.

Such cube builds just fine, but at the query time an NPE is thrown similar to the following:
{quote}Caused by: java.lang.NullPointerException
 at org.apache.kylin.query.relnode.OLAPAggregateRel.rewriteAggregateCall(OLAPAggregateRel.java:561)
 at org.apache.kylin.query.relnode.OLAPAggregateRel.implementRewrite(OLAPAggregateRel.java:419)
 at org.apache.kylin.query.relnode.OLAPRel$RewriteImplementor.visitChild(OLAPRel.java:174)
 at org.apache.kylin.query.relnode.OLAPSortRel.implementRewrite(OLAPSortRel.java:86)
 at org.apache.kylin.query.relnode.OLAPRel$RewriteImplementor.visitChild(OLAPRel.java:174)
 at org.apache.kylin.query.relnode.OLAPLimitRel.implementRewrite(OLAPLimitRel.java:109)
 at org.apache.kylin.query.relnode.OLAPRel$RewriteImplementor.visitChild(OLAPRel.java:174)
 at org.apache.kylin.query.relnode.OLAPToEnumerableConverter.implement(OLAPToEnumerableConverter.java:100)
 at org.apache.calcite.adapter.enumerable.EnumerableRelImplementor.implementRoot(EnumerableRelImplementor.java:108)
 at org.apache.calcite.adapter.enumerable.EnumerableInterpretable.toBindable(EnumerableInterpretable.java:92)
 at org.apache.calcite.prepare.CalcitePrepareImpl$CalcitePreparingStmt.implement(CalcitePrepareImpl.java:1281)
 at org.apache.calcite.prepare.Prepare.prepareSql(Prepare.java:331)
 at org.apache.calcite.prepare.Prepare.prepareSql(Prepare.java:228)
{quote}
There need to be some checks in the UI and in the Top_N query processing code to ensure that all the required measures are defined (as Top_N is actually dependent on another measure to function properly) and inform the user that Top_N definition is incomplete and cube definition is invalid.



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