Add database versioning

src/Database.cpp

@@ -21,6 +21,8 @@
 #define UNLOCK ;
 #endif
 
+#define DB_VERSION 1
+
 // This is the system default locale, which is US-style. It is used for storage
 // and the default preferred locale
 Locale gDefaultLocale;
@@ -123,6 +125,15 @@ Database::CreateFile(const char* path)
 	// Transaction Status: 10
 	// Currency Symbol/Decimal: 2
 
+	DBCommand(
+		"CREATE TABLE db_version (version INTEGER PRIMARY KEY);",
+		"DatabaseCreateFile:create db_version");
+	BString command;
+	command << "INSERT INTO db_version (version) VALUES (" << DB_VERSION << ");";
+	DBCommand(
+		command.String(),
+		"Database::CreateFile:create db_version");
+
 	DBCommand(
 		"create table accountlist (accountid int primary key, name varchar(96), "
 		"type varchar(12), status varchar(30));",
@@ -192,6 +203,18 @@ Database::OpenFile(const char* path)
 		return B_ERROR;
 	}
 
+	// Check for and apply DB migrations
+	if (ApplyMigrations() != B_OK) {
+		UNLOCK;
+		ShowAlert("Error upgrading database",
+			"An error occurred while updating the database to the latest version. "
+			"This may affect the functionality of the application.");
+		BString error;
+		error << "Database::ApplyMigrations() failed";
+		ShowBug(error.String());
+		return B_ERROR;
+	 }
+
 	// Populate account list
 	CppSQLite3Query query =
 		DBQuery("select * from accountlist", "Database::OpenFile:get accounts from list");
@@ -1493,3 +1516,47 @@ Database::DBQuery(const char* query, const char* functionname)
 	// this will never be reached - just to shut up the compiler
 	return CppSQLite3Query();
 }
+
+status_t
+Database::ApplyMigrations() {
+	int currentVersion = 0;
+
+	// Check db_version, create if it doesn't exist. Set version to 1
+	CppSQLite3Query query =
+		DBQuery("SELECT name FROM sqlite_master WHERE type='table' AND name='db_version'",
+			"Database::OpenFile:check for db_version table");
+	if (query.eof()) {
+		DBCommand(
+			"CREATE TABLE db_version (version INTEGER PRIMARY KEY);",
+			"DatabaseCreateFile:create db_version");
+		DBCommand(
+			"INSERT INTO db_version (version) VALUES (1);",
+			"Database::CreateFile:create db_version");
+	}
+
+	// Get current db_version
+	query =
+		DBQuery("SELECT version FROM db_version","Database::ApplyMigrations: get currentVersion");
+
+	if (query.eof())
+		ShowBug("Error getting database version.");
+
+	currentVersion = query.getIntField(0);
+
+	// Apply all missing migrations
+	if (currentVersion < 2) {
+		/* Example usage:
+		// Remove an unused column
+		query =
+			DBQuery("ALTER TABLE accountlocale DROP COLUMN dateseparator;",
+			"Database::ApplyMigrations: remove dateseparator");
+		// Update version number
+		query =
+			DBQuery("UPDATE db_version SET version = 2;",
+			"Database::ApplyMigrations:update version");
+		currentVersion = 2;
+		*/
+	}
+
+	return B_OK;
+}

src/Database.h

@@ -54,6 +54,7 @@ class Database : public Notifier {
 	void CreateFile(const char* path);
 	status_t OpenFile(const char* path);
 	void CloseFile(void);
+	status_t ApplyMigrations();
 
 	Account* AddAccount(const char* name, const AccountType& type, const char* status = "Open",
 		const Locale* locale = NULL);