feat(datastore) only include changed fields in update mutations (#1110)

Author: richardmcclellan

aws-api-appsync/src/main/java/com/amplifyframework/datastore/appsync/ModelConverter.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file is distributed
+ * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ * express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+package com.amplifyframework.datastore.appsync;
+
+import com.amplifyframework.core.model.Model;
+import com.amplifyframework.util.GsonFactory;
+import com.amplifyframework.util.GsonObjectConverter;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonElement;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Utility for converting a Model to/from a Map<String, Object>.
+ */
+public final class ModelConverter {
+
+    private ModelConverter() {}
+
+    /**
+     * Convert a Model to a Map<String, Object>.
+     * @param model a Model instance.
+     * @param <T> type of the Model instance.
+     * @return a Map&lt;String, Object&gt; representation of the provided Model instance.
+     */
+    public static <T extends Model> Map<String, Object> toMap(T model) {
+        if (model == null) {
+            return new HashMap<>();
+        }
+        if (model instanceof SerializedModel) {
+            return ((SerializedModel) model).getSerializedData();
+        } else {
+            Gson gson = GsonFactory.instance();
+            JsonElement jsonElement = gson.toJsonTree(model);
+            return GsonObjectConverter.toMap(jsonElement.getAsJsonObject());
+        }
+    }
+
+    /**
+     * Convert a Map&lt;String, Object&gt; to a Model.
+     * @param map a Map&lt;String, Object&gt;.
+     * @param modelClass Class of Model to convert the Map to.
+     * @param <T> type of the Model instance to convert to.
+     * @return a Model instance created from the provided Map.
+     */
+    public static <T extends Model> T fromMap(Map<String, Object> map, Class<T> modelClass) {
+        Gson gson = GsonFactory.instance();
+        String jsonString = gson.toJson(map);
+        return gson.fromJson(jsonString, modelClass);
+    }
+}

aws-api-appsync/src/main/java/com/amplifyframework/datastore/appsync/SerializedModel.java

@@ -44,6 +44,45 @@ private SerializedModel(
         this.modelSchema = modelSchema;
     }
 
+    /**
+     * Creates a SerializedModel from a generated Java Model object.
+     * @param model Model object
+     * @param modelSchema schema for the Model object
+     * @param <T> type of the Model object.
+     * @return SerializedModel equivalent of the Model object.
+     */
+    public static <T extends Model> SerializedModel create(T model, ModelSchema modelSchema) {
+        return SerializedModel.builder()
+                .serializedData(ModelConverter.toMap(model))
+                .modelSchema(modelSchema)
+                .build();
+    }
+
+    /**
+     * Computes the difference between two Models, comparing equality of each field value for each Model, and returns
+     * the difference as a SerializedModel.
+     * @param updated the updated Model, whose values will be used to build the resulting SerializedModel.
+     * @param original the original Model to compare against.
+     * @param modelSchema ModelSchema for the Models between compared.
+     * @param <T> type of the Models being compared.
+     * @return a SerializedModel, containing only the values from the updated Model that are different from the
+     *         corresponding values in original.
+     */
+    public static <T extends Model> SerializedModel difference(T updated, T original, ModelSchema modelSchema) {
+        Map<String, Object> updatedMap = ModelConverter.toMap(updated);
+        Map<String, Object> originalMap = ModelConverter.toMap(original);
+        Map<String, Object> patchMap = new HashMap<>();
+        for (String key : updatedMap.keySet()) {
+            if ("id".equals(key) || !ObjectsCompat.equals(originalMap.get(key), updatedMap.get(key))) {
+                patchMap.put(key, updatedMap.get(key));
+            }
+        }
+        return SerializedModel.builder()
+                .serializedData(patchMap)
+                .modelSchema(modelSchema)
+                .build();
+    }
+
     /**
      * Return a builder of {@link SerializedModel}.
      * @return A serialized model builder

aws-datastore/src/androidTest/java/com/amplifyframework/datastore/storage/sqlite/SQLiteStorageAdapterSaveTest.java

@@ -17,9 +17,14 @@
 
 import android.util.Log;
 
+import com.amplifyframework.AmplifyException;
+import com.amplifyframework.core.model.Model;
+import com.amplifyframework.core.model.ModelSchema;
 import com.amplifyframework.core.model.query.predicate.QueryPredicate;
 import com.amplifyframework.datastore.DataStoreException;
 import com.amplifyframework.datastore.StrictMode;
+import com.amplifyframework.datastore.appsync.SerializedModel;
+import com.amplifyframework.datastore.storage.StorageItemChange;
 import com.amplifyframework.datastore.storage.SynchronousStorageAdapter;
 import com.amplifyframework.testmodels.commentsblog.AmplifyModelProvider;
 import com.amplifyframework.testmodels.commentsblog.Blog;
@@ -30,10 +35,14 @@
 import org.junit.BeforeClass;
 import org.junit.Test;
 
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Map;
+import java.util.concurrent.TimeUnit;
 
 import io.reactivex.rxjava3.core.Observable;
+import io.reactivex.rxjava3.observers.TestObserver;
 
 import static org.hamcrest.CoreMatchers.containsString;
 import static org.hamcrest.MatcherAssert.assertThat;
@@ -276,4 +285,41 @@ public void saveModelWithPredicateUpdatesConditionally() throws DataStoreExcepti
                 .blockingGet()
         );
     }
+
+    /**
+     * Verify that saving an item that already exists emits a StorageItemChange event with a patchItem that only
+     * contains the fields that are different.
+     *
+     * @throws AmplifyException On failure to obtain ModelSchema from model class.
+     * @throws InterruptedException If interrupted while awaiting terminal result in test observer
+     */
+    @Test
+    public void patchItemOnlyHasChangedFields() throws AmplifyException, InterruptedException {
+        // Create a BlogOwner.
+        final BlogOwner johnSmith = BlogOwner.builder()
+                .name("John Smith")
+                .wea("ther")
+                .build();
+        adapter.save(johnSmith);
+
+        // Start observing for changes
+        TestObserver<StorageItemChange<? extends Model>> observer = adapter.observe().test();
+
+        // Update one field on the BlogOwner.
+        BlogOwner johnAdams = johnSmith.copyOfBuilder().name("John Adams").build();
+        adapter.save(johnAdams);
+
+        // Observe that the StorageItemChange contains an item with only the fields that changed (`id`, and `name`, but
+        // not `wea`)
+        Map<String, Object> serializedData = new HashMap<>();
+        serializedData.put("id", johnAdams.getId());
+        serializedData.put("name", "John Adams");
+        SerializedModel expectedItem = SerializedModel.builder()
+                .serializedData(serializedData)
+                .modelSchema(ModelSchema.fromModelClass(BlogOwner.class))
+                .build();
+        observer.await(1, TimeUnit.SECONDS);
+        observer.assertValueCount(1);
+        observer.assertValueAt(0, storageItemChange -> storageItemChange.patchItem().equals(expectedItem));
+    }
 }

aws-datastore/src/main/java/com/amplifyframework/datastore/appsync/AppSyncRequestFactory.java

@@ -341,7 +341,14 @@ private static Map<String, Object> extractFieldLevelData(
             try {
                 final ModelAssociation association = schema.getAssociations().get(fieldName);
                 if (association == null) {
-                    result.put(fieldName, extractFieldValue(modelField, instance));
+                    if (instance instanceof SerializedModel) {
+                        Map<String, Object> serializedData = ((SerializedModel) instance).getSerializedData();
+                        if (serializedData.containsKey(modelField.getName())) {
+                            result.put(fieldName, serializedData.get(modelField.getName()));
+                        }
+                    } else {
+                        result.put(fieldName, extractFieldValue(modelField, instance));
+                    }
                 } else if (association.isOwner()) {
                     result.put(association.getTargetName(), extractAssociateId(modelField, instance));
                 }

aws-datastore/src/main/java/com/amplifyframework/datastore/storage/StorageItemChange.java

@@ -21,6 +21,7 @@
 import com.amplifyframework.core.model.Model;
 import com.amplifyframework.core.model.ModelSchema;
 import com.amplifyframework.core.model.query.predicate.QueryPredicate;
+import com.amplifyframework.datastore.appsync.SerializedModel;
 
 import java.util.Objects;
 import java.util.UUID;
@@ -37,6 +38,7 @@ public final class StorageItemChange<T extends Model> {
     private final Type type;
     private final QueryPredicate predicate;
     private final T item;
+    private final SerializedModel patchItem;
     private final ModelSchema modelSchema;
 
     private StorageItemChange(
@@ -45,12 +47,14 @@ private StorageItemChange(
             Type type,
             QueryPredicate predicate,
             T item,
+            SerializedModel patchItem,
             ModelSchema modelSchema) {
         this.changeId = changeId;
         this.initiator = initiator;
         this.type = type;
         this.predicate = predicate;
         this.item = item;
+        this.patchItem = patchItem;
         this.modelSchema = modelSchema;
     }
 
@@ -101,6 +105,15 @@ public T item() {
         return item;
     }
 
+    /**
+     * Gets a SerializedModel containing only the fields that have changed.
+     * @return a SerializedModel containing only the fields that have changed.
+     */
+    @NonNull
+    public SerializedModel patchItem() {
+        return patchItem;
+    }
+
     /**
      * Gets the schema of the changed item.
      * @return Schema of changed item
@@ -183,6 +196,7 @@ public static final class Builder<T extends Model> {
         private Type type;
         private QueryPredicate predicate;
         private T item;
+        private SerializedModel patchItem;
         private ModelSchema modelSchema;
 
         /**
@@ -256,6 +270,16 @@ public Builder<T> item(@NonNull T item) {
             return this;
         }
 
+        /**
+         * Configures the patchItem, a SerializedModel containing only the fields that changed.
+         * @param patchItem Representation of the changes that occurred.
+         * @return Current Builder instance for fluent configuration chaining.
+         */
+        public Builder<T> patchItem(@NonNull SerializedModel patchItem) {
+            this.patchItem = Objects.requireNonNull(patchItem);
+            return this;
+        }
+
         /**
          * Configures the schema of the item that changed.
          * @param modelSchema Schema of the item that changed
@@ -281,6 +305,7 @@ public StorageItemChange<T> build() {
                 Objects.requireNonNull(type),
                 Objects.requireNonNull(predicate),
                 Objects.requireNonNull(item),
+                Objects.requireNonNull(patchItem),
                 Objects.requireNonNull(modelSchema)
             );
         }