iOS Sqlite DB Backup and Restore

CHANGELOG-Unreleased.md

@@ -17,6 +17,7 @@
 - [adapters] Adapter objects now returns `dbName`
 - [TypeScript] Add unsafeExecute method
 - [TypeScript] Add localStorage property to Database
+- [iOS] Added ability to backup and restore sqlite db with `database.writeToFile(filePath)` and `database.readFromFile(filePath)`.
 
 ### Performance
 

native/shared/Database.cpp

@@ -914,4 +914,54 @@ jsi::Value Database::getLocal(jsi::String &key) {
     return jsi::String::createFromUtf8(rt, text);
 }
 
+void Database::loadOrSaveDb(jsi::String &zFilename, int isSave) {
+
+    auto &rt = getRt();
+    sqlite3 *pInMemory = db_->sqlite;
+
+    int rc;                   /* Function return code */
+    sqlite3 *pFile;           /* Database connection opened on zFilename */
+    sqlite3_backup *pBackup;  /* Backup object used to copy data */
+    sqlite3 *pTo;             /* Database to copy to (pFile or pInMemory) */
+    sqlite3 *pFrom;           /* Database to copy from (pFile or pInMemory) */
+
+    /* Open the database file identified by zFilename. Exit early if this fails
+     ** for any reason. */
+    rc = sqlite3_open(zFilename.utf8(rt).c_str(), &pFile);
+    if( rc==SQLITE_OK ){
+
+        /* If this is a 'load' operation (isSave==0), then data is copied
+         ** from the database file just opened to database pInMemory.
+         ** Otherwise, if this is a 'save' operation (isSave==1), then data
+         ** is copied from pInMemory to pFile.  Set the variables pFrom and
+         ** pTo accordingly. */
+        pFrom = (isSave ? pInMemory : pFile);
+        pTo   = (isSave ? pFile     : pInMemory);
+
+        /* Set up the backup procedure to copy from the "main" database of
+         ** connection pFile to the main database of connection pInMemory.
+         ** If something goes wrong, pBackup will be set to NULL and an error
+         ** code and  message left in connection pTo.
+         **
+         ** If the backup object is successfully created, call backup_step()
+         ** to copy data from pFile to pInMemory. Then call backup_finish()
+         ** to release resources associated with the pBackup object.  If an
+         ** error occurred, then  an error code and message will be left in
+         ** connection pTo. If no error occurred, then the error code belonging
+         ** to pTo is set to SQLITE_OK.
+         */
+        pBackup = sqlite3_backup_init(pTo, "main", pFrom, "main");
+        if( pBackup ){
+            (void)sqlite3_backup_step(pBackup, -1);
+            (void)sqlite3_backup_finish(pBackup);
+        }
+        rc = sqlite3_errcode(pTo);
+    }
+
+    /* Close the database connection opened on database file zFilename
+     ** and return the result of this function. */
+    (void)sqlite3_close(pFile);
+//    return rc;
+}
+
 } // namespace watermelondb

native/shared/Database.h

@@ -32,6 +32,7 @@ class Database : public jsi::HostObject {
     void unsafeResetDatabase(jsi::String &schema, int schemaVersion);
     jsi::Value getLocal(jsi::String &key);
     void executeMultiple(std::string sql);
+    void loadOrSaveDb(jsi::String &fileName, int isSave);
 
 private:
     bool initialized_;

native/shared/DatabaseInstallation.cpp

@@ -264,6 +264,14 @@ void Database::install(jsi::Runtime *runtime) {
                 std::abort();
             }
         });
+        createMethod(rt, adapter, "loadOrSaveDb", 2, [database](jsi::Runtime &rt, const jsi::Value *args) {
+            assert(database->initialized_);
+            jsi::String filePath = args[0].getString(rt);
+            int isSave = (int)args[1].asBool();
+
+            database->loadOrSaveDb(filePath, isSave);
+            return jsi::Value::undefined();
+        });
         createMethod(rt, adapter, "unsafeClose", 0, [database](jsi::Runtime &rt, const jsi::Value *args) {
             assert(database->initialized_);
             database->destroy();

src/Database/index.js

@@ -269,6 +269,16 @@ export default class Database {
     }
   }
 
+  async writeToFile(filePath: string): Promise<void> {
+    const result = await this.adapter.loadOrSaveDb(filePath, true)
+    return result
+  }
+
+  async readFromFile(filePath: string): Promise<void> {
+    const result = await this.adapter.loadOrSaveDb(filePath, false)
+    return result
+  }
+
   _ensureInWriter(diagnosticMethodName: string): void {
     invariant(
       this._workQueue.isWriterRunning,

src/adapters/compat.js

@@ -97,6 +97,10 @@ export default class DatabaseAdapterCompat {
     return toPromise((callback) => this.underlyingAdapter.removeLocal(key, callback))
   }
 
+  loadOrSaveDb(filePath: string, isSave: boolean): Promise<void> {
+    return toPromise((callback) => this.underlyingAdapter.loadOrSaveDb(filePath, isSave, callback))
+  }
+
   // untyped - test-only code
   async testClone(options: any): Promise<any> {
     // $FlowFixMe

src/adapters/lokijs/index.js

@@ -234,6 +234,10 @@ export default class LokiJSAdapter implements DatabaseAdapter {
     this._dispatcher.call('removeLocal', [key], callback)
   }
 
+  loadOrSaveDb(filePath: string, isSave: boolean, callback: ResultCallback<void>): void {
+    callback({ error: new Error('loadOrSaveDb unavailable on LokiJS') })
+  }
+
   // dev/debug utility
   get _driver(): any {
     // $FlowFixMe

src/adapters/sqlite/index.d.ts

@@ -59,6 +59,8 @@ declare module '@nozbe/watermelondb/adapters/sqlite' {
 
     setLocal(key: string, value: string): Promise<void>
 
+    loadOrSaveDb(filePath: string, isSave: Boolean): Promise<void>
+
     unsafeClearCachedRecords(): Promise<void>
 
     unsafeResetDatabase(): Promise<void>

src/adapters/sqlite/index.js

@@ -375,6 +375,10 @@ export default class SQLiteAdapter implements DatabaseAdapter {
     this._dispatcher.call('batch', [[operation]], callback)
   }
 
+  loadOrSaveDb(filePath: string, isSave: boolean, callback: ResultCallback<void>): void {
+    this._dispatcher.call('loadOrSaveDb', [filePath, isSave], callback)
+  }
+
   removeLocal(key: string, callback: ResultCallback<void>): void {
     const operation = [IGNORE_CACHE, null, `delete from "local_storage" where "key" == ?`, [[key]]]
     this._dispatcher.call('batch', [[operation]], callback)

src/adapters/sqlite/type.js

@@ -73,6 +73,7 @@ export type SqliteDispatcherMethod =
   | 'unsafeResetDatabase'
   | 'getLocal'
   | 'unsafeExecuteMultiple'
+  | 'loadOrSaveDb'
 
 export interface SqliteDispatcher {
   call(methodName: SqliteDispatcherMethod, args: any[], callback: ResultCallback<any>): void;

src/adapters/type.d.ts

@@ -77,4 +77,7 @@ export interface DatabaseAdapter {
 
   // Removes key from local storage
   removeLocal(key: string, callback: ResultCallback<void>): void;
+
+  // Backup / restore db: load from or save into filePath
+  loadOrSaveDb(filePath: string, isSave: Boolean, callback: ResultCallback<void>): void;
 }

src/adapters/type.js

@@ -79,4 +79,7 @@ export interface DatabaseAdapter {
 
   // Removes key from local storage
   removeLocal(key: string, callback: ResultCallback<void>): void;
+
+  // Backup / restore db: load from or save into filePath
+  loadOrSaveDb(filePath: string, isSave: boolean, callback: ResultCallback<void>): void;
 }