feat(loki): add optional flag for Changes API to limit update operati…

…on output to modified properties only (#29)

Also includes properties flagged as unique, since they would be needed to identify the item that is updated. (from techfort/LokiJS#578)

packages/loki/spec/generic/changesApi.spec.js

@@ -55,4 +55,42 @@ describe("changesApi", () => {
 
     expect(users.getChanges().length).toEqual(0);
   });
+
+  it("works with delta mode", function () {
+    const db = new loki(),
+      options = {
+        asyncListeners: false,
+        disableChangesApi: false,
+        disableDeltaChangesApi: false
+      },
+      items = db.addCollection("items", options);
+
+    // Add some documents to the collection
+    items.insert({name: "mjolnir", owner: "thor", maker: {name: "dwarves", count: 1}});
+    items.insert({name: "gungnir", owner: "odin", maker: {name: "elves", count: 1}});
+    items.insert({name: "tyrfing", owner: "Svafrlami", maker: {name: "dwarves", count: 1}});
+    items.insert({name: "draupnir", owner: "odin", maker: {name: "elves", count: 1}});
+
+    // Find and update an existing document
+    const tyrfing = items.findOne({"name": "tyrfing"});
+    tyrfing.owner = "arngrim";
+    items.update(tyrfing);
+    tyrfing.maker.count = 4;
+    items.update(tyrfing);
+
+    let changes = db.serializeChanges(["items"]);
+    changes = JSON.parse(changes);
+
+    expect(changes.length).toEqual(6);
+
+    const firstUpdate = changes[4];
+    expect(firstUpdate.operation).toEqual("U");
+    expect(firstUpdate.obj.owner).toEqual("arngrim");
+    expect(firstUpdate.obj.name).toBeUndefined();
+
+    const secondUpdate = changes[5];
+    expect(secondUpdate.operation).toEqual("U");
+    expect(secondUpdate.obj.owner).toBeUndefined();
+    expect(secondUpdate.obj.maker).toEqual({count: 4});
+  });
 });

packages/loki/src/collection.js

@@ -85,6 +85,7 @@ export class Collection extends LokiEventEmitter {
    * @param {boolean} [options.adaptiveBinaryIndices=true] - collection indices will be actively rebuilt rather than lazily
    * @param {boolean} [options.asyncListeners=false] - whether listeners are invoked asynchronously
    * @param {boolean} [options.disableChangesApi=true] - set to false to enable Changes API
+   * @param {boolean} [options.disableDeltaChangesApi=true] - set to false to enable Delta Changes API (requires Changes API, forces cloning)
    * @param {boolean} [options.autoupdate=false] - use Object.observe to update objects automatically
    * @param {boolean} [options.clone=false] - specify whether inserts and queries clone to/from user
    * @param {boolean} [options.serializableIndices =true[]] - converts date values on binary indexed property values are serializable
@@ -171,6 +172,12 @@ export class Collection extends LokiEventEmitter {
     // disable track changes
     this.disableChangesApi = options.disableChangesApi !== undefined ? options.disableChangesApi : true;
 
+    // disable delta update object style on changes
+    this.disableDeltaChangesApi = options.disableDeltaChangesApi !== undefined ? options.disableDeltaChangesApi : true;
+    if (this.disableChangesApi) {
+      this.disableDeltaChangesApi = true;
+    }
+
     // option to observe objects and update them automatically, ignored if Object.observe is not supported
     this.autoupdate = options.autoupdate !== undefined ? options.autoupdate : false;
 
@@ -258,14 +265,54 @@ export class Collection extends LokiEventEmitter {
      * This method creates a clone of the current status of an object and associates operation and collection name,
      * so the parent db can aggregate and generate a changes object for the entire db
      */
-    function createChange(name, op, obj) {
+    function createChange(name, op, obj, old) {
       self.changes.push({
         name,
         operation: op,
-        obj: JSON.parse(JSON.stringify(obj))
+        obj: op === "U" && !self.disableDeltaChangesApi ? getChangeDelta(obj, old) : JSON.parse(JSON.stringify(obj))
       });
     }
 
+    //Compare changed object (which is a forced clone) with existing object and return the delta
+    function getChangeDelta(obj, old) {
+      if (old) {
+        return getObjectDelta(old, obj);
+      }
+      else {
+        return JSON.parse(JSON.stringify(obj));
+      }
+    }
+
+    this.getChangeDelta = getChangeDelta;
+
+    function getObjectDelta(oldObject, newObject) {
+      const propertyNames = newObject !== null && typeof newObject === "object" ? Object.keys(newObject) : null;
+      if (propertyNames && propertyNames.length && ["string", "boolean", "number"].indexOf(typeof(newObject)) < 0) {
+        const delta = {};
+        for (let i = 0; i < propertyNames.length; i++) {
+          const propertyName = propertyNames[i];
+          if (newObject.hasOwnProperty(propertyName)) {
+            if (!oldObject.hasOwnProperty(propertyName) || self.uniqueNames.indexOf(propertyName) >= 0 || propertyName === "$loki" || propertyName === "meta") {
+              delta[propertyName] = newObject[propertyName];
+            }
+            else {
+              const propertyDelta = getObjectDelta(oldObject[propertyName], newObject[propertyName]);
+              if (typeof propertyDelta !== "undefined" && propertyDelta !== {}) {
+                delta[propertyName] = propertyDelta;
+              }
+            }
+          }
+        }
+        return Object.keys(delta).length === 0 ? undefined : delta;
+      }
+      else {
+        return oldObject === newObject ? undefined : newObject;
+      }
+    }
+
+    this.getObjectDelta = getObjectDelta;
+
+
     // clear all the changes
     function flushChanges() {
       self.changes = [];
@@ -323,18 +370,18 @@ export class Collection extends LokiEventEmitter {
       createChange(self.name, "I", obj);
     }
 
-    function createUpdateChange(obj) {
-      createChange(self.name, "U", obj);
+    function createUpdateChange(obj, old) {
+      createChange(self.name, "U", obj, old);
     }
 
     function insertMetaWithChange(obj) {
       insertMeta(obj);
       createInsertChange(obj);
     }
 
-    function updateMetaWithChange(obj) {
+    function updateMetaWithChange(obj, old) {
       updateMeta(obj);
-      createUpdateChange(obj);
+      createUpdateChange(obj, old);
     }
 
 
@@ -352,6 +399,9 @@ export class Collection extends LokiEventEmitter {
 
     this.setChangesApi = (enabled) => {
       this.disableChangesApi = !enabled;
+      if (!enabled) {
+        self.disableDeltaChangesApi = false;
+      }
       setHandlers();
     };
     /**
@@ -361,8 +411,8 @@ export class Collection extends LokiEventEmitter {
       insertHandler(obj);
     });
 
-    this.on("update", (obj) => {
-      updateHandler(obj);
+    this.on("update", (obj, old) => {
+      updateHandler(obj, old);
     });
 
     this.on("delete", (obj) => {
@@ -418,7 +468,10 @@ export class Collection extends LokiEventEmitter {
   }
 
   static fromJSONObject(obj, options, forceRebuild) {
-    let coll = new Collection(obj.name, {disableChangesApi: obj.disableChangesApi});
+    let coll = new Collection(obj.name, {
+      disableChangesApi: obj.disableChangesApi,
+      disableDeltaChangesApi: obj.disableDeltaChangesApi
+    });
 
     coll.adaptiveBinaryIndices = obj.adaptiveBinaryIndices !== undefined ? (obj.adaptiveBinaryIndices === true) : false;
     coll.transactional = obj.transactional;
@@ -1016,7 +1069,7 @@ export class Collection extends LokiEventEmitter {
       position = arr[1]; // position in data array
 
       // if configured to clone, do so now... otherwise just use same obj reference
-      newInternal = this.cloneObjects ? clone(doc, this.cloneMethod) : doc;
+      newInternal = this.cloneObjects  || !this.disableDeltaChangesApi ? clone(doc, this.cloneMethod) : doc;
 
       this.emit("pre-update", doc);
 
@@ -1059,7 +1112,7 @@ export class Collection extends LokiEventEmitter {
       this.commit();
       this.dirty = true; // for autosave scenarios
 
-      this.emit("update", doc, this.cloneObjects ? clone(oldInternal, this.cloneMethod) : null);
+      this.emit("update", doc, this.cloneObjects  || !this.disableDeltaChangesApi ? clone(oldInternal, this.cloneMethod) : null);
       return doc;
     } catch (err) {
       this.rollback();

packages/loki/src/event_emitter.js

@@ -13,24 +13,24 @@ export class LokiEventEmitter {
 
   constructor() {
     /**
-		 * @prop {hashmap} events - a hashmap, with each property being an array of callbacks
-		 */
+     * @prop {hashmap} events - a hashmap, with each property being an array of callbacks
+     */
     this.events = {};
 
     /**
-		 * @prop {boolean} asyncListeners - boolean determines whether or not the callbacks associated with each event
-		 * should happen in an async fashion or not
-		 * Default is false, which means events are synchronous
-		 */
+     * @prop {boolean} asyncListeners - boolean determines whether or not the callbacks associated with each event
+     * should happen in an async fashion or not
+     * Default is false, which means events are synchronous
+     */
     this.asyncListeners = false;
   }
 
   /**
-	 * on(eventName, listener) - adds a listener to the queue of callbacks associated to an event
-	 * @param {string|string[]} eventName - the name(s) of the event(s) to listen to
-	 * @param {function} listener - callback function of listener to attach
-	 * @returns {int} the index of the callback in the array of listeners for a particular event
-	 */
+   * on(eventName, listener) - adds a listener to the queue of callbacks associated to an event
+   * @param {string|string[]} eventName - the name(s) of the event(s) to listen to
+   * @param {function} listener - callback function of listener to attach
+   * @returns {int} the index of the callback in the array of listeners for a particular event
+   */
   on(eventName, listener) {
     let event;
 
@@ -50,43 +50,43 @@ export class LokiEventEmitter {
   }
 
   /**
-	 * emit(eventName, data) - emits a particular event
-	 * with the option of passing optional parameters which are going to be processed by the callback
-	 * provided signatures match (i.e. if passing emit(event, arg0, arg1) the listener should take two parameters)
-	 * @param {string} eventName - the name of the event
-	 * @param {object} data - optional object passed with the event
-	 */
-  emit(eventName, data) {
+   * emit(eventName, data) - emits a particular event
+   * with the option of passing optional parameters which are going to be processed by the callback
+   * provided signatures match (i.e. if passing emit(event, arg0, arg1) the listener should take two parameters)
+   * @param {string} eventName - the name of the event
+   * @param {object} data - optional object passed with the event
+   */
+  emit(eventName, ...data) {
     if (eventName && this.events[eventName]) {
       this.events[eventName].forEach((listener) => {
         if (this.asyncListeners) {
           setTimeout(() => {
-            listener(data);
+            listener(...data);
           }, 1);
         } else {
-          listener(data);
+          listener(...data);
         }
 
       });
     }
   }
 
   /**
-	 * Alias of LokiEventEmitter.prototype.on
-	 * addListener(eventName, listener) - adds a listener to the queue of callbacks associated to an event
-	 * @param {string|string[]} eventName - the name(s) of the event(s) to listen to
-	 * @param {function} listener - callback function of listener to attach
-	 * @returns {int} the index of the callback in the array of listeners for a particular event
-	 */
+   * Alias of LokiEventEmitter.prototype.on
+   * addListener(eventName, listener) - adds a listener to the queue of callbacks associated to an event
+   * @param {string|string[]} eventName - the name(s) of the event(s) to listen to
+   * @param {function} listener - callback function of listener to attach
+   * @returns {int} the index of the callback in the array of listeners for a particular event
+   */
   addListener(eventName, listener) {
     return this.on(eventName, listener);
   }
 
   /**
-	 * removeListener() - removes the listener at position 'index' from the event 'eventName'
-	 * @param {string|string[]} eventName - the name(s) of the event(s) which the listener is attached to
-	 * @param {function} listener - the listener callback function to remove from emitter
-	 */
+   * removeListener() - removes the listener at position 'index' from the event 'eventName'
+   * @param {string|string[]} eventName - the name(s) of the event(s) which the listener is attached to
+   * @param {function} listener - the listener callback function to remove from emitter
+   */
   removeListener(eventName, listener) {
     if (Array.isArray(eventName)) {
       eventName.forEach((currentEventName) => {

packages/loki/src/resultset.js

@@ -976,6 +976,12 @@ export class Resultset {
       forceCloneMethod = "shallow";
     }
 
+    // if collection has delta changes active, then force clones and use 'parse-stringify' for effective change tracking of nested objects
+    if (!this.collection.disableDeltaChangesApi) {
+      forceClones = true;
+      forceCloneMethod = "parse-stringify";
+    }
+
     // if this has no filters applied, just return collection.data
     if (!this.filterInitialized) {
       if (this.filteredrows.length === 0) {