import com.hp.hpl.jena.sparql.algebra.op.OpConditional; //导入依赖的package包/类
@Override
public String translate(String _resultName) {
    resultName = _resultName;
    String leftJoin = "-- " + Tags.LEFT_JOIN + "\n";

    if (opLeftJoin.getExprs() == null) {
        OpConditional opCond = new OpConditional(opLeftJoin.getLeft(), opLeftJoin.getRight());
        PigConditional pigCond = new PigConditional(opCond, getLeft(), getRight(), prefixes);
        leftJoin = pigCond.translate(_resultName);
        varsWithNulls = pigCond.getVarsWithNulls();
        resultSchema = pigCond.getSchema();
    }
    else {
        varsWithNulls.addAll(leftOp.getVarsWithNulls());
        varsWithNulls.addAll(rightOp.getVarsWithNulls());
        leftJoin += generateLeftJoin();
    }

    return leftJoin;
}
 

import com.hp.hpl.jena.sparql.algebra.op.OpConditional; //导入依赖的package包/类
@Override
public void visit(OpConditional opConditional) {
}
 

import com.hp.hpl.jena.sparql.algebra.op.OpConditional; //导入依赖的package包/类
public PigConditional(OpConditional _opConditional, PigOp _leftOp, PigOp _rightOp, PrefixMapping _prefixes) {
    super(_leftOp, _rightOp, _prefixes);
    opConditional = _opConditional;
    resultName = Tags.CONDITIONAL;
}
 

import com.hp.hpl.jena.sparql.algebra.op.OpConditional; //导入依赖的package包/类
public void visit(OpConditional opCondition) {
	// TODO moving down / improvements possible!! Check this
	wrapInCurrentFilterAndRecurse(opCondition);
}
 

import com.hp.hpl.jena.sparql.algebra.op.OpConditional; //导入依赖的package包/类
@Override
public Op transform(OpConditional opCond, Op left, Op right) {
	return substitute(opCond, left, right);
}
 

import com.hp.hpl.jena.sparql.algebra.op.OpConditional; //导入依赖的package包/类
@Override
public Op transform(OpConditional opCond, Op left, Op right) {
	return mergeToBGP(left, right);
}