Hi Aegeaner, First of all, the ExpressionReducer actually restores the origin return type after reducing, see https://github.com/apache/flink/blob/master/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/codegen/ExpressionReducer.scala#L122
So the reduced result and type should be correct. Did you find the wrong return type? The `RexBuilder.makeLiteral(Object value, RelDataType type, boolean allowCast)` accepts any values and will cast Integer back to Date internally. Regards, Jark Wu 2017-06-29 12:38 GMT+08:00 郭健 <guo.j...@immomo.com>: > Hi all, > I am implementing a STR_TO_DATE scalar SQL function to flink, > and found return type casted from java.sql.Date to Integer in Flink’s > ExpressionReducer： > https://github.com/apache/flink/blob/master/flink- > libraries/flink-table/src/main/scala/org/apache/flink/table/codegen/ > ExpressionReducer.scala#L56 > > // we need to cast here for RexBuilder.makeLiteral > > > case (SqlTypeName.DATE, e) => > > > Some( > > > > rexBuilder.makeCast(typeFactory.createTypeFromTypeInfo(BasicTypeInfo.INT_TYPE_INFO), > e) > > > ) > > > > so str_to_date('01,5,2013','%d,%m,%Y')" must return an > Integer, which conflicted with my implementation. > > My question is: why should we do this? I have seen in comments > the reason to do this here is: “we need to cast here for > RexBuilder.makeLiteral”, But is it reasonale to change user function’s > return Type? Should we restore the origin return type after the reduce? > > > Thanks, > Aegeaner > > >
