Add update_time to SQLLiteRemoteDocument schema

Author: schmidt-sebastian

firebase-firestore/src/main/java/com/google/firebase/firestore/local/SQLiteRemoteDocumentCache.java

@@ -18,6 +18,7 @@
 import static com.google.firebase.firestore.util.Assert.hardAssert;
 
 import androidx.annotation.Nullable;
+import com.google.firebase.Timestamp;
 import com.google.firebase.database.collection.ImmutableSortedMap;
 import com.google.firebase.firestore.core.Query;
 import com.google.firebase.firestore.model.Document;
@@ -51,13 +52,18 @@ final class SQLiteRemoteDocumentCache implements RemoteDocumentCache {
   @Override
   public void add(MaybeDocument maybeDocument) {
     String path = pathForKey(maybeDocument.getKey());
+    Timestamp timestamp = maybeDocument.getVersion().getTimestamp();
     MessageLite message = serializer.encodeMaybeDocument(maybeDocument);
 
     statsCollector.recordRowsWritten(STATS_TAG, 1);
 
     db.execute(
-        "INSERT OR REPLACE INTO remote_documents (path, contents) VALUES (?, ?)",
+        "INSERT OR REPLACE INTO remote_documents "
+            + "(path, update_time_seconds, update_time_nanos, contents) "
+            + "VALUES (?, ?, ?, ?)",
         path,
+        timestamp.getSeconds(),
+        timestamp.getNanoseconds(),
         message.toByteArray());
 
     db.getIndexManager().addToCollectionParentIndex(maybeDocument.getKey().getPath().popLast());

firebase-firestore/src/main/java/com/google/firebase/firestore/local/SQLiteSchema.java

@@ -45,8 +45,16 @@ class SQLiteSchema {
   /**
    * The version of the schema. Increase this by one for each migration added to runMigrations
    * below.
+   *
+   * <p>TODO(index-free): The migration to schema version 9 doesn't backfill `update_time` as this
+   * requires rewriting the RemoteDocumentCache. For index-free queries to efficiently handle
+   * existing documents, we still need to populate update_time for all existing entries, drop the
+   * RemoteDocumentCache or ask users to invoke `clearPersistence()` manually. If we decide to
+   * backfill or drop the contents of the RemoteDocumentCache, we need to perform an additional
+   * schema migration.
    */
-  static final int VERSION = 8;
+  static final int VERSION = 9;
+
   // Remove this constant and increment VERSION to enable indexing support
   static final int INDEXING_SUPPORT_VERSION = VERSION + 1;
 
@@ -127,6 +135,10 @@ void runMigrations(int fromVersion, int toVersion) {
       createV8CollectionParentsIndex();
     }
 
+    if (fromVersion < 9 && toVersion >= 9) {
+      addUpdateTime();
+    }
+
     /*
      * Adding a new migration? READ THIS FIRST!
      *
@@ -351,6 +363,16 @@ private void addSequenceNumber() {
     }
   }
 
+  private void addUpdateTime() {
+    if (!tableContainsColumn("remote_documents", "update_time_seconds")) {
+      hardAssert(
+          !tableContainsColumn("remote_documents", "update_time_nanos"),
+          "Table contained update_time_seconds, but is missing update_time_nanos");
+      db.execSQL("ALTER TABLE remote_documents ADD COLUMN update_time_seconds INTEGER");
+      db.execSQL("ALTER TABLE remote_documents ADD COLUMN update_time_nanos INTEGER");
+    }
+  }
+
   /**
    * Ensures that each entry in the remote document cache has a corresponding sentinel row. Any
    * entries that lack a sentinel row are given one with the sequence number set to the highest