Uses one query for installation dedup (parse-community#2281)

Author: flovilmart

src/RestWrite.js

@@ -582,65 +582,83 @@ RestWrite.prototype.handleInstallation = function() {
   var promise = Promise.resolve();
 
   var idMatch; // Will be a match on either objectId or installationId
+  var objectIdMatch;
+  var installationIdMatch;
   var deviceTokenMatches = [];
 
+  // Instead of issuing 3 reads, let's do it with one OR.
+  let orQueries = [];
   if (this.query && this.query.objectId) {
-    promise = promise.then(() => {
-      return this.config.database.find('_Installation', {
+    orQueries.push({
         objectId: this.query.objectId
-      }, {}).then((results) => {
-        if (!results.length) {
-          throw new Parse.Error(Parse.Error.OBJECT_NOT_FOUND,
+    });
+  }
+  if (this.data.installationId) {
+    orQueries.push({
+      'installationId': this.data.installationId
+    });
+  }
+  if (this.data.deviceToken) {
+    orQueries.push({'deviceToken': this.data.deviceToken});
+  }
+
+  if (orQueries.length == 0) {
+    return;
+  }
+
+  promise = promise.then(() => {
+    return this.config.database.find('_Installation', {
+        '$or': orQueries
+    }, {});
+  }).then((results) => {
+    results.forEach((result) => {
+      if (this.query && this.query.objectId && result.objectId == this.query.objectId) {
+        objectIdMatch = result;
+      }
+      if (result.installationId == this.data.installationId) {
+        installationIdMatch = result;
+      }
+      if (result.deviceToken == this.data.deviceToken) {
+        deviceTokenMatches.push(result);
+      }
+    });
+
+    // Sanity checks when running a query
+    if (this.query && this.query.objectId) {
+      if (!objectIdMatch) {
+        throw new Parse.Error(Parse.Error.OBJECT_NOT_FOUND,
                                 'Object not found for update.');
-        }
-        idMatch = results[0];
-        if (this.data.installationId && idMatch.installationId &&
-          this.data.installationId !== idMatch.installationId) {
+      }
+      if (this.data.installationId && objectIdMatch.installationId &&
+          this.data.installationId !== objectIdMatch.installationId) {
           throw new Parse.Error(136,
                                 'installationId may not be changed in this ' +
                                 'operation');
         }
-        if (this.data.deviceToken && idMatch.deviceToken &&
-          this.data.deviceToken !== idMatch.deviceToken &&
-          !this.data.installationId && !idMatch.installationId) {
+        if (this.data.deviceToken && objectIdMatch.deviceToken &&
+          this.data.deviceToken !== objectIdMatch.deviceToken &&
+          !this.data.installationId && !objectIdMatch.installationId) {
           throw new Parse.Error(136,
                                 'deviceToken may not be changed in this ' +
                                 'operation');
         }
         if (this.data.deviceType && this.data.deviceType &&
-          this.data.deviceType !== idMatch.deviceType) {
+          this.data.deviceType !== objectIdMatch.deviceType) {
           throw new Parse.Error(136,
                                 'deviceType may not be changed in this ' +
                                 'operation');
         }
-        return;
-      });
-    });
-  }
-
-  // Check if we already have installations for the installationId/deviceToken
-  promise = promise.then(() => {
-    if (this.data.installationId) {
-      return this.config.database.find('_Installation', {
-        'installationId': this.data.installationId
-      });
-    }
-    return Promise.resolve([]);
-  }).then((results) => {
-    if (results && results.length) {
-      // We only take the first match by installationId
-      idMatch = results[0];
     }
-    if (this.data.deviceToken) {
-      return this.config.database.find(
-        '_Installation',
-        {'deviceToken': this.data.deviceToken});
+
+    if (this.query && this.query.objectId && objectIdMatch) {
+      idMatch = objectIdMatch;
     }
-    return Promise.resolve([]);
-  }).then((results) => {
-    if (results) {
-      deviceTokenMatches = results;
+
+    if (this.data.installationId && installationIdMatch) {
+      idMatch = installationIdMatch;
     }
+
+  }).then(() => {
     if (!idMatch) {
       if (!deviceTokenMatches.length) {
         return;