[CALCITE-3008] Create AuxiliaryConverterFactory

[walterddr]

This fixes: https://issues.apache.org/jira/browse/CALCITE-3008

[hsyuan]

Why do you want pass factory class instead of just interface AuxiliaryConverter in SqlToRelConverter?

[walterddr]

Why do you want pass factory class instead of just interface AuxiliaryConverter in SqlToRelConverter?

That's actually a good point. SqlToRelConverter requires us to generate one AuxiliaryConverter instance for each SqlFunction (e.g. the List), so it would be very inefficient to pass a reflective class object and then call the newInstance method.

I do have the option to change the AuxiliaryConverter API to do

RexNode convert(RexBuilder rexBuilder, RexNode groupCall, RexNode e, SqlFunction sqlCall);

With the extra parameter, we can make the AuxiliaryConverter static. This require to change a public interface which I hesitated to do so.

Any advice?

[hsyuan]

Let's discuss in JIRA.

[walterddr]

close and opened #1219