From 87f4fc8f3fd0f6a2025d84646b84efaaa32e2299 Mon Sep 17 00:00:00 2001
From: Raphael Kim <raphk@amazon.com>
Date: Tue, 3 Dec 2019 17:49:29 -0800
Subject: [PATCH] [DataStore] Implement delete cascade

---
 .../SQLiteStorageAdapterInstrumentedTest.java | 35 ++++++++++++++++++-
 .../storage/sqlite/SQLiteCommandFactory.java  |  4 ++-
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/aws-datastore/src/androidTest/java/com/amplifyframework/datastore/storage/sqlite/SQLiteStorageAdapterInstrumentedTest.java b/aws-datastore/src/androidTest/java/com/amplifyframework/datastore/storage/sqlite/SQLiteStorageAdapterInstrumentedTest.java
index 6f2d730be2..59530402d5 100644
--- a/aws-datastore/src/androidTest/java/com/amplifyframework/datastore/storage/sqlite/SQLiteStorageAdapterInstrumentedTest.java
+++ b/aws-datastore/src/androidTest/java/com/amplifyframework/datastore/storage/sqlite/SQLiteStorageAdapterInstrumentedTest.java
@@ -480,7 +480,7 @@ public void queryWithMaliciousPredicates() throws DataStoreException {
     }
 
     /**
-     * Assert that save stores item in the SQLite database correctly.
+     * Assert that delete deletes item in the SQLite database correctly.
      * @throws DataStoreException from possible underlying DataStore exceptions
      */
     @Test
@@ -499,6 +499,39 @@ public void deleteModelDeletesData() throws DataStoreException {
         assertFalse(iterator.hasNext());
     }
 
+    /**
+     * Assert that delete deletes item in the SQLite database without
+     * violating foreign key constraints.
+     * @throws DataStoreException from possible underlying DataStore exceptions
+     */
+    @Test
+    public void deleteModelCascades() throws DataStoreException {
+        // Triggers an insert
+        final BlogOwner raphael = BlogOwner.builder()
+                .name("Raphael Kim")
+                .build();
+        saveModel(raphael);
+
+        // Triggers a foreign key constraint check
+        final Blog raphaelsBlog = Blog.builder()
+                .name("Raphael's Blog")
+                .owner(raphael)
+                .build();
+        saveModel(raphaelsBlog);
+
+        // Triggers a delete
+        // Deletes Raphael's Blog also to prevent foreign key violation
+        deleteModel(raphael);
+
+        // Get the BlogOwner record from the database
+        Iterator<BlogOwner> blogOwnerterator = queryModel(BlogOwner.class);
+        assertFalse(blogOwnerterator.hasNext());
+
+        // Get the Blog record from the database
+        Iterator<Blog> blogIterator = queryModel(Blog.class);
+        assertFalse(blogIterator.hasNext());
+    }
+
     private <T extends Model> T saveModel(@NonNull T model) throws DataStoreException {
         LatchedResultListener<StorageItemChange.Record> saveListener =
             LatchedResultListener.waitFor(SQLITE_OPERATION_TIMEOUT_MS);
diff --git a/aws-datastore/src/main/java/com/amplifyframework/datastore/storage/sqlite/SQLiteCommandFactory.java b/aws-datastore/src/main/java/com/amplifyframework/datastore/storage/sqlite/SQLiteCommandFactory.java
index 3074122028..d4626d93fe 100644
--- a/aws-datastore/src/main/java/com/amplifyframework/datastore/storage/sqlite/SQLiteCommandFactory.java
+++ b/aws-datastore/src/main/java/com/amplifyframework/datastore/storage/sqlite/SQLiteCommandFactory.java
@@ -381,7 +381,9 @@ private StringBuilder parseForeignKeys(SQLiteTable table) {
                     .append("REFERENCES")
                     .append(SqlKeyword.DELIMITER)
                     .append(connectedType)
-                    .append("(" + connectedId + ")");
+                    .append("(" + connectedId + ")")
+                    .append(SqlKeyword.DELIMITER)
+                    .append("ON DELETE CASCADE");
 
             if (foreignKeyIterator.hasNext()) {
                 builder.append(",").append(SqlKeyword.DELIMITER);