@Override
    public RexNode visitCall(RexCall inputCall) {
      RexNode node = super.visitCall(inputCall);
      if (node instanceof RexCall) {
        RexCall call = (RexCall) node;
        if (HiveIn.INSTANCE.equals(call.op)) {
          return transformIntoOrAndClause(rexBuilder, call);
        }
      }
      return RexUtil.isFlat(node) ? node : RexUtil.flatten(rexBuilder, node);
    }
Transforms IN clauses into OR/AND clauses, when possible.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/jdbc/JDBCExpandExpressionsRule.java