import com.hp.hpl.jena.sparql.algebra.op.OpExtend; //导入依赖的package包/类
public void visit(OpExtend opExtend) {
	// TODO Might be able to move down filter past the OpExtend
	wrapInCurrentFilterAndRecurse(opExtend);
}
 

import com.hp.hpl.jena.sparql.algebra.op.OpExtend; //导入依赖的package包/类
@Override
public void visit(OpExtend opExtend) {
	variables.addAll(opExtend.getVarExprList().getVars());
}
 

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

import com.hp.hpl.jena.sparql.algebra.op.OpExtend; //导入依赖的package包/类
@Override
public Op transform(OpExtend opExtend, Op subOp) {
	return new OpBGP();
}
 

import com.hp.hpl.jena.sparql.algebra.op.OpExtend; //导入依赖的package包/类
public ExtendRouter(ExecContext context, OpExtend op, OpRouter sub) {
    super(context, op, sub);
    this.exprs = op.getVarExprList();
}