I’m Maramreddy Pranaykumar Reddy and I’d like to work on a “good first issue”: adding the missing Join operator to the wayang-generic-jdbc platform. Right now, Join exists in wayang-postgres (via JdbcJoinOperator), but wayang-generic-jdbc does not expose a Join mapping/operator yet.
*Proposed approach* Add GenericJdbcJoinOperator (extends JdbcJoinOperator, implements GenericJdbcExecutionOperator). Add genericjdbc/mapping/JoinMapping (similar to postgres/mapping/JoinMapping) and register it in genericjdbc/mapping/Mappings. Extend GenericJdbcExecutor to include JOIN clauses when generating SQL (mirroring the join handling in JdbcExecutor#createSqlString). *Constraint*: Generic JDBC can only push down a SQL JOIN when both inputs are reachable from the same JDBC instance/connection (same jdbcName). If they differ, the join must not be compiled into a single SQL query and should fall back to another platform/operator. *Tests*: Add a test that asserts the generated SQL includes the expected JOIN ... ON ... for same-jdbcName joins, plus a negative test for different jdbcNames (no invalid SQL join / fallback behavior).
