Calcite. Correlated expressions with subquery can be planned.

statement ok
CREATE TABLE integers(i INTEGER)

statement ok
INSERT INTO integers VALUES (1), (2), (3), (NULL)

# union with correlated expression
query II
SELECT i, (SELECT i FROM integers WHERE i=i1.i UNION SELECT i FROM integers WHERE i=i1.i) AS j FROM integers i1 ORDER BY i NULLS FIRST;
----
NULL	NULL
1	1
2	2
3	3

# join on two subqueries that both have a correlated expression in them
query II
SELECT i, (SELECT s1.i FROM (SELECT i FROM integers WHERE i=i1.i) s1 INNER JOIN (SELECT i FROM integers WHERE i=4-i1.i) s2 ON s1.i>s2.i) AS j FROM integers i1 ORDER BY i;
----
NULL	NULL
1	NULL
2	NULL
3	3

/subquery/scalar/test_complex_correlated_subquery.test[_ignore]

org.apache.ignite.internal.processors.query.calcite.exec.ExecutionServiceImplc{1}] Unexpected error at query optimizer.
org.apache.calcite.plan.RelOptPlanner$CannotPlanException: There are not enough rules to produce a node with desired properties: convention=IGNITE, sort=[0 ASC-nulls-first], distr=single, rewindability=one-way, correlation=uncorrelated.
Missing conversions are LogicalFilter[convention: NONE -> IGNITE, distr: any -> random], IgniteUnionAll[sort: [] -> [0]], LogicalFilter[convention: NONE -> IGNITE, sort: [] -> [0], distr: any -> random, rewindability: one-way -> rewindable], LogicalFilter[convention: NONE -> IGNITE, distr: any -> single], LogicalFilter[convention: NONE -> IGNITE, distr: any -> single, rewindability: one-way -> rewindable]
There are 5 empty subsets: