The main thing it that the UD(A)F framework can deduce the SQL type of the parameters and return value of the function. If a function returns Number, should the SQL type be DECIMAL(p, s), or INTEGER, or BIGINT, or DOUBLE? None of these options is perfect. If there isn’t an obvious winner, I don’t know whether we should allow Number.
Maybe we should add an annotation, similar to Parameter[5], that allows you to specify the SQL return type of a UDF. In this case, a Java function could return, say, a SQL BIGINT even if its return type was Object, Number or String. Regarding Object[]. I think that is the type of a *row* (due to the JavaRowFormat.ARRAY in [1]) not the type of a particular column. There have been bugs due to inconsistencies — Calcite sometimes uses an Object to represent a single-column row, and sometimes uses an Object[]. Maybe you’re running into a bug of that kind. Julian [5] https://calcite.apache.org/apidocs/org/apache/calcite/linq4j/function/Parameter.html <https://calcite.apache.org/apidocs/org/apache/calcite/linq4j/function/Parameter.html> > On Dec 26, 2016, at 10:03 PM, Arun Iyer <[email protected]> wrote: > > We have a UDAF that returns “Number” as the result type. We use > RexToLixTranslator to generate java code [1]. In the generated code, the > value of the field with Number type is cast to Object[] and the compilation > fails. > > When I trace the flow, I see that in PhysTypeImpl the field classes are > determined via javaRowClass method [2]. The type for the Number field turns > out to be “BasicSqlType(Other)” and the javaRowClass [3] returns a > “Object[]”. Somewhere down the line the field value is then cast to > “Object[]” in the generate code [4]. > > Just wondering why Object[] is returned (should unknown fields be mapped to > Object instead?). Also is it possible to write UDAFs that return super types > like Number (so that it can work for any sub type) but the return type does > not directly map to SQL types? > > Thanks, > Arun > > [1] > https://github.com/apache/storm/blob/master/external/sql/storm-sql-core/src/jvm/org/apache/storm/sql/compiler/RexNodeToBlockStatementCompiler.java#L73 > [2] > https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/adapter/enumerable/PhysTypeImpl.java#L75 > [3] > https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/adapter/enumerable/EnumUtils.java#L96 > [4] > https://gist.github.com/arunmahadevan/35809494467d5636e31c0031f81d9aa7#file-test-java-L149 > >
