finish altering migration framework

util/src/migration/mod.rs

@@ -57,51 +57,12 @@ impl From<::std::io::Error> for Error {
 	}
 }
 
-/// Migration source.
-pub trait Source {
-	/// Get an iterator over the key, value pairs.
-	fn iter(&self) -> Box<Iterator<Item=(Vec<u8>, Vec<u8>)>>;
-
-	/// Query a specific key.
-	fn get(&self, key: &[u8]) -> Option<Vec<u8>>;
-}
-
-impl Source for Database {
-	fn iter(&self) -> Box<Iterator<Item=(Vec<u8>, Vec<u8>)>> {
-		Box::new(self.iter().map(|(k, v)| (k.to_vec(), v.to_vec())))
-	}
-
-	fn get(&self, key: &[u8]) -> Option<Vec<u8>> {
-		self.get(key).ok().and_then(|x| x).map(|x| x.to_owned())
-	}
-}
-
-
-
-/// Object being migrated
-pub trait Migrateable {
-	/// Called on destination to commit batch of migrated entries.
-	fn commit(&mut self, batch: &BTreeMap<Vec<u8>, Vec<u8>>) -> Result<(), Error>;
-}
-
-impl Migrateable for Database {
-	fn commit(&mut self, batch: &BTreeMap<Vec<u8>, Vec<u8>>) -> Result<(), Error> {
-		let transaction = DBTransaction::new();
-
-		for keypair in batch {
-			try!(transaction.put(&keypair.0, &keypair.1).map_err(Error::Custom))
-		}
-
-		self.write(transaction).map_err(Error::Custom)
-	}
-}
-
 /// A generalized migration from the given db to a destination db.
 pub trait Migration: 'static {
 	/// Version of the database after the migration.
 	fn version(&self) -> u32;
 	/// Migrate a source to a destination.
-	fn migrate(&self, source: &Source, config: &Config, destination: &mut Destination) -> Result<(), Error>;
+	fn migrate(&self, source: &Database, config: &Config, destination: &mut Database) -> Result<(), Error>;
 }
 
 /// A simple migration over key-value pairs.
@@ -116,7 +77,7 @@ pub trait SimpleMigration: 'static {
 impl<T: SimpleMigration> Migration for T {
 	fn version(&self) -> u32 { SimpleMigration::version(self) }
 
-	fn migrate(&self, source: &Source, config: &Config, destination: &mut Destination) -> Result<(), Error> {
+	fn migrate(&self, source: &Database, config: &Config, dest: &mut Database) -> Result<(), Error> {
 		let mut batch: BTreeMap<Vec<u8>, Vec<u8>> = BTreeMap::new();
 
 		for (key, value) in source.iter() {
@@ -126,17 +87,27 @@ impl<T: SimpleMigration> Migration for T {
 			}
 
 			if batch.len() == config.batch_size {
-				try!(destination.commit(&batch));
+				try!(commit_batch(dest, &batch));
-				batch.clear();
 			}
 		}
 
-		try!(destination.commit(&batch));
+		try!(commit_batch(dest, &batch));
 
 		Ok(())
 	}
 }
 
+/// Commit a batch of writes to a database.
+pub fn commit_batch(db: &mut Database, batch: &BTreeMap<Vec<u8>, Vec<u8>>) -> Result<(), Error> {
+	let transaction = DBTransaction::new();
+
+	for keypair in batch {
+		try!(transaction.put(&keypair.0, &keypair.1).map_err(Error::Custom));
+	}
+
+	db.write(transaction).map_err(Error::Custom)
+}
+
 /// Get the path where all databases reside.
 fn database_path(path: &Path) -> PathBuf {
 	let mut temp_path = path.to_owned();
@@ -144,30 +115,29 @@ fn database_path(path: &Path) -> PathBuf {
 	temp_path
 }
 
-// which temp database we are currently using
+enum TempIdx {
-enum TempDB {
 	One,
 	Two,
 }
 
-impl TempDB {
+impl TempIdx {
-	// given the path that all databases reside in,
+	fn swap(&mut self) {
-	// return the path of this one.
-	fn path(&self, db_path: &Path) -> PathBuf {
-		let mut path = db_path.to_owned();
 		match *self {
-			TempDB::One => path.push("migration_1"),
+			TempIdx::One => *self = TempIdx::Two,
-			TempDB::Two => path.push("migration_2"),
+			TempIdx::Two => *self = TempIdx::One,
 		}
-
-		path
 	}
 
-	fn swap(&mut self) {
+	// given the path to the old database, get the path of this one.
-		*self = match *self {
+	fn path(&self, db_root: &Path) -> PathBuf {
-			TempDB::One => TempDB::Two,
+		let mut buf = db_root.to_owned();
-			TempDB::Two => TempDB::One,
+
+		match *self {
+			TempIdx::One => buf.push("temp_migration_1"),
+			TempIdx::Two => buf.push("temp_migration_2"),
 		};
+
+		buf
 	}
 }
 
@@ -199,10 +169,9 @@ impl Manager {
 		}
 	}
 
-	/// Performs migrations in order. This alternates migrating between two
+	/// Performs migration in order, starting with a source path, migrating between two temporary databases,
-	/// temporary databases, and returns the path to the final one used.
+	/// and producing a path where the final migration lives.
-	/// The other is deleted by this function.
+	pub fn execute(&self, old_path: &Path, version: u32) -> Result<PathBuf, Error> {
-	pub fn execute(&self, db_path: PathBuf, version: u32) -> Result<PathBuf, Error> {
 		let migrations = try!(self.migrations_from(version).ok_or(Error::MigrationImpossible));
 		let db_config = DatabaseConfig {
 			prefix_size: None,
@@ -211,15 +180,16 @@ impl Manager {
 			compaction: CompactionProfile::default(),
 		};
 
-		let mut temp_db = TempDB::One;
+		let db_root = database_path(old_path);
-		let mut temp_path = temp_db.path(&db_path);
+		let mut temp_idx = TempIdx::One;
+		let mut temp_path = temp_idx.path(&db_root);
 
 		// start with the old db.
 		let old_path_str = try!(old_path.to_str().ok_or(Error::MigrationImpossible));
 		let mut cur_db = try!(Database::open(&db_config, old_path_str).map_err(|s| Error::Custom(s)));
 		for migration in migrations {
 			// open the target temporary database.
-			temp_path = temp_db.path(&db_path);
+			temp_path = temp_idx.path(&db_root);
 			let temp_path_str = try!(temp_path.to_str().ok_or(Error::MigrationImpossible));
 			let mut new_db = try!(Database::open(&db_config, temp_path_str).map_err(|s| Error::Custom(s)));
 
@@ -227,10 +197,10 @@ impl Manager {
 			try!(migration.migrate(&cur_db, &self.config, &mut new_db));
 			// next iteration, we will migrate from this db into the other temp.
 			cur_db = new_db;
-			temp_db.swap();
+			temp_idx.swap();
 
 			// remove the other temporary migration database.
-			let _ = fs::remove_dir_all(temp_db.path(&db_path));
+			let _ = fs::remove_dir_all(temp_idx.path(&db_root));
 		}
 		Ok(temp_path)
 	}