Method connect

src/org/apache/pig/impl/plan/OperatorPlan.java:174–204

Create an edge between two nodes. The direction of the edge implies data flow. @param from Operator data will flow from. @param to Operator data will flow to. @throws PlanException if this edge will create multiple inputs for an operator that does not support multiple inputs or create multiple outp

(E from, E to)

     * for an operator that does not support multiple outputs.
     */
    public void connect(E from, E to) throws PlanException {
        markDirty();

        // Check that both nodes are in the plan.
        checkInPlan(from);
        checkInPlan(to);

        // Check to see if the from operator already has outputs, and if so
        // whether it supports multiple outputs.
        if (mFromEdges.get(from) != null &&
                !from.supportsMultipleOutputs()) {
            PlanException pe = new PlanException("Attempt to give operator of type " +
                from.getClass().getName() + " multiple outputs.  This operator does "
                + "not support multiple outputs.");
            log.error(pe.getMessage());
            throw pe;
        }

        // Check to see if the to operator already has inputs, and if so
        // whether it supports multiple inputs.
        if (mToEdges.get(to) != null &&
                !to.supportsMultipleInputs()) {
            PlanException pe =  new PlanException("Attempt to give operator of type " +
                to.getClass().getName() + " multiple inputs.  This operator does "
                + "not support multiple inputs.");
            log.error(pe.getMessage());
            throw pe;
        }
        mFromEdges.put(from, to);
        mToEdges.put(to, from);
    }
    
    /**
     * Create an soft edge between two nodes.