Disable the subquery

[luoc]

Hello Calcite team,


  I am going to develop a new feature on my project with the Calcite. But 
got the following issues :


Input SQL :


SELECT A.N_NAME, B.R_NAME FROM V1.NATION A LEFT JOIN V1.REGION B ON 
A.N_REGIONKEY = B.R_REGIONKEY WHERE B.R_NAME = 'ASIA';


Actual SQL (send to DB) :


SELECT "NATION0"."N_NAME" AS "n_name", "t"."R_NAME" AS "r_name"
FROM "V1"."NATION" AS "NATION0"
INNER JOIN (SELECT *
FROM "V1"."REGION"
WHERE "R_NAME" = 'ASIA') AS "t" ON "NATION0"."N_REGIONKEY" = "t"."R_REGIONKEY";


If possible, How can I disable the join auto-convert to the subquery syntax? 
Because the backend DB does not support the subquery (but the `left join` is 
supported). Add the specified rule or rewrite the `JdbcJoinRule` class ?


Thanks for your time.