Major Description
At the moment UNION/CROSS/JOIN allow 1 operand.
You can write:-
b = UNION a ; c = CROSS b ; d = JOIN c BY $0 ;
Possibly UNION with 1 operand might be needed for implementing Sigma-styled union (Ui=1..n An) but for CROSS/JOIN I think nobody would do such operation.
By simply replacing "*" with "+" in the parser tree should fix this problem. Should this be fixed?
LogicalOperator CrossClause() : {LogicalOperator op; ArrayList<OperatorKey> inputs = new ArrayList<OperatorKey>();}
{
(
op = NestedExpr() { inputs.add(op.getOperatorKey()); }
("," op = NestedExpr() { inputs.add(op.getOperatorKey()); })*
)
{return rewriteCross(inputs);}
}
LogicalOperator JoinClause() : {CogroupInput gi; ArrayList<CogroupInput> gis = new ArrayList<CogroupInput>();}
{
(gi = GroupItem() { gis.add(gi); }
("," gi = GroupItem() { gis.add(gi); })*)
{return rewriteJoin(gis);}
}
LogicalOperator UnionClause() : {LogicalOperator op; ArrayList<OperatorKey> inputs = new ArrayList<OperatorKey>();}
{
(op = NestedExpr() { inputs.add(op.getOperatorKey()); }
("," op = NestedExpr() { inputs.add(op.getOperatorKey()); })*)
{return new LOUnion(opTable, scope, getNextId(), inputs);}
}