Hi,
We used to face the same problem overriding the default behavior including
operand type checker of a standard operator. If you are using Calcite as an
individual planner (or other circumstances you are not taking the Calcite's
default planner tool org.apache.calcite.prepare.PlannerImpl)
There are two main steps you'd have to take here. Firstly, you'd have
to change the operand types accepted by CONCAT in SqlStdOperatorTable.
Second, you'd have to redefine the CONCAT method in RexImpTable to
something that actually builds the string instead of just using
String.concat.
I am using Calcite to try to be a federated database server for a BI tool.
This BI tool is sending queries that I cannot change at the source. So, I
am trying to do some customizations within Calcite to handle these
queries.
For instance, one of the queries tries to do a sql concatenate between
