/**
* Return best iterator for computing a given logical join, given the specified statistics, and
* the provided left and right subplans. Note that there is insufficient information to determine
* which plan should be the inner/outer here -- because DbIterator's don't provide any cardinality
* estimates, and stats only has information about the base tables. For this reason, the plan1
*
* @param lj The join being considered
* @param plan1 The left join node's child
* @param plan2 The right join node's child
*/
public static DbIterator instantiateJoin(LogicalJoinNode lj, DbIterator plan1, DbIterator plan2)
throws ParsingException {
int t1id = 0, t2id = 0;
DbIterator j;
try {
t1id = plan1.getTupleDesc().fieldNameToIndex(lj.f1QuantifiedName);
} catch (NoSuchElementException e) {
throw new ParsingException("Unknown field " + lj.f1QuantifiedName);
}
if (lj instanceof LogicalSubplanJoinNode) {
t2id = 0;
} else {
try {
t2id = plan2.getTupleDesc().fieldNameToIndex(lj.f2QuantifiedName);
} catch (NoSuchElementException e) {
throw new ParsingException("Unknown field " + lj.f2QuantifiedName);
}
}
JoinPredicate p = new JoinPredicate(t1id, lj.p, t2id);
j = new Join(p, plan1, plan2);
return j;
}
