This issue is specific to MONGO 2.6 server.

When we try to run the following query against MongoDB BI Connector 2.6 on MongoDB 4.0.2 server then it throws the ERROR: error cross join optimizer: expected PlanStage for table dbcert.t4, got <nil>
SQLState: HY000
ErrorCode: 1105

PLEASE NOTE: This issue does not occur when we use the same query against MongoDB BI Connector 2.7 on MongoDB 4.0.3 and MongoDB BI Connector 2.8 on MongoDB 4.0.5

QUERY:

SELECT
`t1`.`col1` AS `C1`,
`t1`.`col2` AS `C2`,
`t1`.`col3` AS `C3`
FROM
`dbName`.`Table1` `t2`,
`dbName`.`Table1` `t3`,
(
SELECT
`col2`,
1 AS `c2`
FROM
`dbName`.`Table1`
WHERE
`col2` IN (
'P1',
'c' )
) `t4`,
(
SELECT
`col1`,
`col2`,
`col3`
FROM
`dbName`.`tsupply`
WHERE
`col1` = 'S1' AND
`col2` = 'P1'
) `t1`
WHERE
`t2`.`col2` = `t1`.`col2` AND
`t2`.`col2` = `t4`.`col2` AND
`t2`.`col2` = `t3`.`col2` AND
`t2`.`col2` IN (
'P1',
'a' ) AND
`t3`.`col2` IN (
'P1',
'b' )
ORDER BY
`C3` ASC