Supporting counter column operations

Author: masumsoft

README.md

@@ -164,8 +164,28 @@ Express cassandra exposes some node driver methods for convenience. To generate
 *   `models.timeuuid()`  
     returns a type 1 (time-based) uuid, suitable for Cassandra `timeuuid` fields, as a string
 *   `models.consistencies`
-    this object contains all the available consistency enums defined by cassandra driver, so you can for example use models.consistencies.one, models.consistencies.quorum etc.
+    this object contains all the available consistency enums defined by node cassandra driver, so you can for example use models.consistencies.one, models.consistencies.quorum etc.
+*   `models.datatypes`
+    this object contains all the available datatypes defined by node cassandra driver, so you can for example use
+    models.datatypes.Long to deal with the cassandra bigint or counter field types.
 
+### Counter Column Operations
+
+Cassandra counter column increment and decrement operations are supported via the update operation. To increment/decrement a counter, you can use the following types of update operation:
+
+```js
+//Say your model name is StatsModel that has a user_id as the primary key and visit_count as a counter column.
+
+models.instance.Stats.update({user_id:1234}, {visit_count:2}, function(err){
+    //visit_count will be incremented by 2
+});
+
+models.instance.Stats.update({user_id:1234}, {visit_count:-1}, function(err){
+    //visit_count will be decremented by 1
+});
+```
+
+Please note that counter columns has special limitations, to know more about the counter column usage, see the <a href="http://docs.datastax.com/en/cql/3.1/cql/cql_using/use_counter_t.html">cassandra docs</a>.
 
 ### Support for Composite Data Types
 

lib/expressCassandra.js

@@ -93,6 +93,10 @@ module.exports = {
         return cql.types.consistencies;
     },
 
+    get datatypes() {
+        return cql.types;
+    },
+
     _translateFileNameToModelName : function(fileName) {
         return fileName
             .slice(	0,

lib/orm/base_model.js

@@ -549,6 +549,18 @@ BaseModel._get_db_value_expression = function(fieldname, fieldvalue){
             if(retvalset.length > 1) retvalset = retvalset.slice(0,retvalset.length-1);
             retvalset += "}";
             return retvalset;
+        case 'counter':
+            var retvalcounter = fieldname;
+            if(fieldvalue > 0) {
+                retvalcounter += " + " + fieldvalue;
+            }
+            else if(fieldvalue < 0) {
+                retvalcounter += " - " + Math.abs(fieldvalue);
+            }
+            else {
+                throw(build_error('model.value.invalidvalue',fieldvalue,fieldname,fieldtype));
+            }
+            return retvalcounter;
         default:
             return fieldvalue;
     }

test/models/CounterModel.js

@@ -0,0 +1,7 @@
+module.exports = {
+    "fields": {
+        "user_id": "bigint",
+        "visit_count": "counter"
+    },
+    "key" : ["user_id"]
+}

test/test.js

@@ -240,6 +240,29 @@ describe('Unit Tests', function(){
         });
     });
 
+    describe('#update counter column',function(){
+        it('should increment the counter to 2', function(done) {
+            models.instance.Counter.update({user_id:1234}, {visit_count:2}, function(err){
+                if(err) throw err;
+                models.instance.Counter.findOne({user_id:1234}, function(err, stats){
+                    if(err) throw err;
+                    stats.visit_count.toString().should.equal('2');
+                    done();
+                });
+            });
+        });
+        it('should decrement the counter to 0', function(done) {
+            models.instance.Counter.update({user_id:1234}, {visit_count:-2}, function(err){
+                if(err) throw err;
+                models.instance.Counter.findOne({user_id:1234}, function(err, stats){
+                    if(err) throw err;
+                    stats.visit_count.toString().should.equal('0');
+                    done();
+                });
+            });
+        });
+    });
+
     describe('#close cassandra connection',function(){
         it('should close connection to cassandra without errors', function(done) {
             models.close(function(err){