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ASF GitHub Bot commented on DRILL-4783: --------------------------------------- Github user jinfengni commented on a diff in the pull request: https://github.com/apache/drill/pull/546#discussion_r71630181 --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/flatten/FlattenRecordBatch.java --- @@ -129,11 +129,21 @@ private void setFlattenVector() { try { final TypedFieldId typedFieldId = incoming.getValueVectorId(popConfig.getColumn()); final MaterializedField field = incoming.getSchema().getColumn(typedFieldId.getFieldIds()[0]); - final RepeatedValueVector vector = RepeatedValueVector.class.cast(incoming.getValueAccessorById( - field.getValueClass(), typedFieldId.getFieldIds()).getValueVector()); + RepeatedValueVector vector = null; + try { + vector = RepeatedValueVector.class.cast(incoming.getValueAccessorById( + field.getValueClass(), typedFieldId.getFieldIds()).getValueVector()); + } catch(ClassCastException ex) { --- End diff -- In stead of catch ClassCastException, you may check if the input value vector is an instance of RepeatedValueVector. Using try{} catch{} seems a bit over-kill for this case. > Flatten on CONVERT_FROM fails with ClassCastException if resultset is empty > --------------------------------------------------------------------------- > > Key: DRILL-4783 > URL: https://issues.apache.org/jira/browse/DRILL-4783 > Project: Apache Drill > Issue Type: Bug > Reporter: Chunhui Shi > Assignee: Chunhui Shi > Priority: Critical > > Flatten failed to work on top of convert_from when the resultset is empty. > For a HBase table like this: > 0: jdbc:drill:zk=localhost:5181> select convert_from(t.address.cities,'json') > from hbase.`/tmp/flattentest` t; > +----------------------------------------------------------------------------------+ > | EXPR$0 > | > +----------------------------------------------------------------------------------+ > | {"list":[{"city":"SunnyVale"},{"city":"Palo Alto"},{"city":"Mountain > View"}]} | > | {"list":[{"city":"Seattle"},{"city":"Bellevue"},{"city":"Renton"}]} > | > | {"list":[{"city":"Minneapolis"},{"city":"Falcon Heights"},{"city":"San > Paul"}]} | > +----------------------------------------------------------------------------------+ > Flatten works when row_key is in (1,2,3) > 0: jdbc:drill:zk=localhost:5181> select flatten(t1.json.list) from (select > convert_from(t.address.cities,'json') json from hbase.`/tmp/flattentest` t > where row_key=1) t1; > +---------------------------+ > | EXPR$0 | > +---------------------------+ > | {"city":"SunnyVale"} | > | {"city":"Palo Alto"} | > | {"city":"Mountain View"} | > +---------------------------+ > But Flatten throws exception if the resultset is empty > 0: jdbc:drill:zk=localhost:5181> select flatten(t1.json.list) from (select > convert_from(t.address.cities,'json') json from hbase.`/tmp/flattentest` t > where row_key=4) t1; > Error: SYSTEM ERROR: ClassCastException: Cannot cast > org.apache.drill.exec.vector.NullableIntVector to > org.apache.drill.exec.vector.complex.RepeatedValueVector > Fragment 0:0 > [Error Id: 07fd0cab-d1e6-4259-bfec-ad80f02d93a2 on atsqa4-127.qa.lab:31010] > (state=,code=0) -- This message was sent by Atlassian JIRA (v6.3.4#6332)