InfinityDB

Our Answer:

Please read ItemSpace Data Structures.html or ItemSpace DataStructures.pdf for the basics on the Entity-Attribute-Value model we will use here. You could also structure this as a relational system, but EAV is more fun. You would define an EntityClass, which is just the EAV name for a table:

    static final EntityClass METRICS = new EntityClass(0); // the 'table'

    static final Attribute METRIC = new Attribute(0); // the 'column'

    static void insertMetricReport(String factoryId,
	            String machineId, Date date, long metric) throws IOException {
	    Cu cu = Cu.alloc(); // get a work cursor temporarily

	    // create a new METRIC report entry if necessary, identified by 
	    // factoryId, machine id, and date and attach the metric to it.
	    cu.append(METRICS) // the EntityClass component
	    .append(factoryId) // next three components are the composite key
	    .append(machineId)
	    .append(date)
	    .append(METRIC) // the Attibute component is like a column name
	    .append(metric); // the Value component
	    db.insert(cu); // put all of them into db in one atomic action
	
	    Cu.dispose(cu); // Give back cursor for speed. no strictly necessary
	}

    void selectReports(String factoryId, String machineId,  
            Date startDate) throws IOException {
	    Cu cu = Cu.alloc()
	    	.append(METRICS)
	    	.append(factoryId)
	    	.append(machineId);
	    int protectedPrefixLength = cu.length(); // The current contents of the Cu is protected
	    cu.append(startDate); // start the scan here. This part is not protected, so it changes
	    while (db.next(cu, protectedPrefixLength)) { // iterate over report dates
	        printMetric(factoryId, machineId, cu.dateAt(protectedPrefixLength));
                // This cookie-cutter code allows iteration over a part of an Entity.
                // More often, this is unnecessary because we iterate over multi-value Attributes.
                cu.setLength(cu.skipComponent(protectedPrefixLength));
                cu.incrementSuffix(protectedPrefixLength);
	    }
	    cu.dispose();
    }

    void printMetric(String factoryId, String machineID, Date reportDate) throws IOException {
        Cu cu = Cu.alloc()
        	.append(METRICS)
        	.append(factoryId)
        	.append(machineID)
        	.append(reportDate)
        	.append(METRIC);
        int protectedPrefix = cu.length();
        if (db.next(cu, protectedPrefix)) { // got a report
            System.out.print("date=" + reportDate + " metric=" + cu.longAt(protectedPrefix));
        }
        cu.dispose();
    }