in tajo-core/tajo-core-backend/src/main/java/org/apache/tajo/engine/planner/physical/MergeFullOuterJoinExec.java [105:312]
public Tuple next() throws IOException {
Tuple previous;
for (;;) {
boolean newRound = false;
if((posRightTupleSlots == -1) && (posLeftTupleSlots == -1)) {
newRound = true;
}
if ((posRightTupleSlots == rightTupleSlots.size()) && (posLeftTupleSlots == leftTupleSlots.size())) {
newRound = true;
}
if(newRound == true){
if (end) {
////////////////////////////////////////////////////////////////////////
// FINALIZING STAGE
////////////////////////////////////////////////////////////////////////
// the finalizing stage, where remaining tuples on the right are
// transformed into left-padded results while tuples on the left
// are transformed into right-padded results
// before exit, a left-padded tuple should be built for all remaining
// right side and a right-padded tuple should be built for all remaining
// left side
if (initRightDone == false) {
// maybe the left operand was empty => the right one didn't have the chance to initialize
rightTuple = rightChild.next();
initRightDone = true;
}
if((leftTuple == null) && (rightTuple == null)) {
return null;
}
if((leftTuple == null) && (rightTuple != null)){
// output a tuple with the nulls padded leftTuple
Tuple nullPaddedTuple = TupleUtil.createNullPaddedTuple(leftNumCols);
frameTuple.set(nullPaddedTuple, rightTuple);
projector.eval(frameTuple, outTuple);
// we simulate we found a match, which is exactly the null padded one
rightTuple = rightChild.next();
return outTuple;
}
if((leftTuple != null) && (rightTuple == null)){
// output a tuple with the nulls padded leftTuple
Tuple nullPaddedTuple = TupleUtil.createNullPaddedTuple(rightNumCols);
frameTuple.set(leftTuple, nullPaddedTuple);
projector.eval(frameTuple, outTuple);
// we simulate we found a match, which is exactly the null padded one
leftTuple = leftChild.next();
return outTuple;
}
} // if end
////////////////////////////////////////////////////////////////////////
// INITIALIZING STAGE
////////////////////////////////////////////////////////////////////////
// initializing stage, reading the first tuple on each side
if (leftTuple == null) {
leftTuple = leftChild.next();
if( leftTuple == null){
end = true;
continue;
}
}
if (rightTuple == null) {
rightTuple = rightChild.next();
initRightDone = true;
if (rightTuple == null) {
end = true;
continue;
}
}
// reset tuple slots for a new round
leftTupleSlots.clear();
rightTupleSlots.clear();
posRightTupleSlots = -1;
posLeftTupleSlots = -1;
////////////////////////////////////////////////////////////////////////
// Comparison and Move Forward Stage
////////////////////////////////////////////////////////////////////////
// advance alternatively on each side until a match is found
int cmp;
while (!end && ((cmp = joincomparator.compare(leftTuple, rightTuple)) != 0)) {
if (cmp > 0) {
//before getting a new tuple from the right, a leftnullpadded tuple should be built
//output a tuple with the nulls padded leftTuple
Tuple nullPaddedTuple = TupleUtil.createNullPaddedTuple(leftNumCols);
frameTuple.set(nullPaddedTuple, rightTuple);
projector.eval(frameTuple, outTuple);
// BEFORE RETURN, MOVE FORWARD
rightTuple = rightChild.next();
if(rightTuple == null) {
end = true;
}
return outTuple;
} else if (cmp < 0) {
// before getting a new tuple from the left, a rightnullpadded tuple should be built
// output a tuple with the nulls padded rightTuple
Tuple nullPaddedTuple = TupleUtil.createNullPaddedTuple(rightNumCols);
frameTuple.set(leftTuple, nullPaddedTuple);
projector.eval(frameTuple, outTuple);
// we simulate we found a match, which is exactly the null padded one
// BEFORE RETURN, MOVE FORWARD
leftTuple = leftChild.next();
if(leftTuple == null) {
end = true;
}
return outTuple;
} // if (cmp < 0)
} //while
////////////////////////////////////////////////////////////////////////
// SLOTS POPULATION STAGE
////////////////////////////////////////////////////////////////////////
// once a match is found, retain all tuples with this key in tuple slots
// on each side
if(!end) {
endInPopulationStage = false;
boolean endLeft = false;
boolean endRight = false;
previous = new VTuple(leftTuple);
do {
leftTupleSlots.add(new VTuple(leftTuple));
leftTuple = leftChild.next();
if(leftTuple == null) {
endLeft = true;
}
} while ((endLeft != true) && (tupleComparator[0].compare(previous, leftTuple) == 0));
posLeftTupleSlots = 0;
previous = new VTuple(rightTuple);
do {
rightTupleSlots.add(new VTuple(rightTuple));
rightTuple = rightChild.next();
if(rightTuple == null) {
endRight = true;
}
} while ((endRight != true) && (tupleComparator[1].compare(previous, rightTuple) == 0) );
posRightTupleSlots = 0;
if ((endLeft == true) || (endRight == true)) {
end = true;
endInPopulationStage = true;
}
} // if end false
} // if newRound
////////////////////////////////////////////////////////////////////////
// RESULTS STAGE
////////////////////////////////////////////////////////////////////////
// now output result matching tuples from the slots
// if either we haven't reached end on neither side, or we did reach end
// on one(or both) sides but that happened in the slots population step
// (i.e. refers to next round)
if(!end || (end && endInPopulationStage)){
if(posLeftTupleSlots == 0){
leftNext = new VTuple (leftTupleSlots.get(posLeftTupleSlots));
posLeftTupleSlots = posLeftTupleSlots + 1;
}
if(posRightTupleSlots <= (rightTupleSlots.size() -1)) {
Tuple aTuple = new VTuple(rightTupleSlots.get(posRightTupleSlots));
posRightTupleSlots = posRightTupleSlots + 1;
frameTuple.set(leftNext, aTuple);
joinQual.eval(inSchema, frameTuple);
projector.eval(frameTuple, outTuple);
return outTuple;
} else {
// right (inner) slots reached end and should be rewind if there are still tuples in the outer slots
if(posLeftTupleSlots <= (leftTupleSlots.size()-1)) {
//rewind the right slots position
posRightTupleSlots = 0;
Tuple aTuple = new VTuple(rightTupleSlots.get(posRightTupleSlots));
posRightTupleSlots = posRightTupleSlots + 1;
leftNext = new VTuple (leftTupleSlots.get(posLeftTupleSlots));
posLeftTupleSlots = posLeftTupleSlots + 1;
frameTuple.set(leftNext, aTuple);
joinQual.eval(inSchema, frameTuple);
projector.eval(frameTuple, outTuple);
return outTuple;
}
}
} // the second if end false
} // for
}