[CALCITE-4118] RexSimplify might remove CAST from RexNode incorrectly

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.23.0, 1.24.0
• Fix Version/s: 1.25.0
• Component/s: core
• Labels: pull-request-available
• Assignee: Chunwei Lei
• Reporter: Shuo Cheng
• Created: 10/Jul/20 03:56
• Updated: 22/Aug/20 18:48
• Resolved: 31/Jul/20 03:52

Description

@Test void testCastError() {
  final String sql = "select cast(cast(count(distinct empno) as varchar(65536)) as varbinary)\n"
      + "from emp group by deptno";
  sql(sql).ok();
}

Consider the above test case, we get the following plan after SqlToRel.

LogicalProject(EXPR$0=[CAST($1):VARBINARY NOT NULL])
      LogicalAggregate(group=[{0}], agg#0=[COUNT(DISTINCT $1)])
        LogicalProject(DEPTNO=[$7], EMPNO=[$0])
          LogicalTableScan(table=[[CATALOG, SALES, EMP]])

As it is shown, `cast(* as varchar)` is removed (by RexSimplify#SimplifyCast), which is obviously wrong, because BIGINT can not cast to VARBINARY.

Issue Links

• is caused by: CALCITE-3712 Optimize lossless casts in RexSimplify: CAST(CAST(intExpr as BIGINT) as INT) => intExpr
• is related to: CALCITE-3979 Simplification might have removed CAST expression(s) incorrectly
• relates to: CALCITE-4081 Round-tripping a DECIMAL literal through Planner -> RelToSqlConverter -> Planner throws validation error
• links to: GitHub Pull Request #2072