Version 0.2.0

Closes #2

README.md

@@ -28,7 +28,7 @@ _ZRM_ provides a simple interface to relational databases in Zig. Define your re
 
 ## Versions
 
-ZRM 0.1.2 is made and tested with zig 0.13.0.
+ZRM 0.2.0 is made and tested with zig 0.13.0.
 
 ## Work in progress
 
@@ -41,7 +41,7 @@ ZRM aims to handle a lot for you, but it takes time to make. Have a look to [the
 In your project directory:
 
 ```shell
-$ zig fetch --save https://code.zeptotech.net/zedd/zrm/archive/v0.1.2.tar.gz
+$ zig fetch --save https://code.zeptotech.net/zedd/zrm/archive/v0.2.0.tar.gz
 ```
 
 In `build.zig`:

build.zig.zon

@@ -1,6 +1,6 @@
 .{
 	.name = "zrm",
-	.version = "0.1.2",
+	.version = "0.2.0",
 
 	.minimum_zig_version = "0.13.0",
 

src/database.zig

@@ -0,0 +1,109 @@
+const std = @import("std");
+const pg = @import("pg");
+const session = @import("session.zig");
+
+/// Abstract connection, provided by a connector.
+pub const Connection = struct {
+	/// Raw connection.
+	connection: *pg.Conn,
+
+	/// Connection implementation.
+	_interface: struct {
+		instance: *anyopaque,
+		release: *const fn (self: *Connection) void,
+	},
+
+	/// Release the connection.
+	pub fn release(self: *Connection) void {
+		self._interface.release(self);
+	}
+};
+
+/// Database connection manager for queries.
+pub const Connector = struct {
+	const Self = @This();
+
+	/// Internal interface structure.
+	_interface: struct {
+		instance: *anyopaque,
+		getConnection: *const fn (self: *anyopaque) anyerror!*Connection,
+	},
+
+	/// Get a connection.
+	pub fn getConnection(self: Self) !*Connection {
+		return try self._interface.getConnection(self._interface.instance);
+	}
+};
+
+
+
+/// A simple pool connection.
+pub const PoolConnection = struct {
+	const Self = @This();
+
+	/// Connector of the connection.
+	connector: *PoolConnector,
+	/// Connection instance, to only keep one at a time.
+	_connection: ?Connection = null,
+
+	/// Get a database connection.
+	pub fn connection(self: *Self) !*Connection {
+		if (self._connection == null) {
+			// A new connection needs to be initialized.
+			self._connection = .{
+				.connection = try self.connector.pool.acquire(),
+				._interface = .{
+					.instance = self,
+					.release = releaseConnection,
+				},
+			};
+		}
+
+		// Return the initialized connection.
+		return &(self._connection.?);
+	}
+
+	// Implementation.
+
+	/// Release the pool connection.
+	fn releaseConnection(self: *Connection) void {
+		self.connection.release();
+
+		// Free allocated connection.
+		const poolConnection: *PoolConnection = @ptrCast(@alignCast(self._interface.instance));
+		poolConnection.connector.pool._allocator.destroy(poolConnection);
+	}
+};
+
+/// A simple pool connector.
+pub const PoolConnector = struct {
+	const Self = @This();
+
+	pool: *pg.Pool,
+
+	/// Get a database connector instance for the current pool.
+	pub fn connector(self: *Self) Connector {
+		return .{
+			._interface = .{
+				.instance = self,
+				.getConnection = getConnection,
+			},
+		};
+	}
+
+	// Implementation.
+
+	/// Get the connection from the pool.
+	fn getConnection(opaqueSelf: *anyopaque) !*Connection {
+		const self: *Self = @ptrCast(@alignCast(opaqueSelf));
+
+		// Initialize a new connection.
+		const poolConnection = try self.pool._allocator.create(PoolConnection);
+		poolConnection.* = .{
+			.connector = self,
+		};
+
+		// Acquire a new connection from the pool.
+		return try poolConnection.connection();
+	}
+};

src/insert.zig

@@ -2,6 +2,7 @@ const std = @import("std");
 const pg = @import("pg");
 const zollections = @import("zollections");
 const errors = @import("errors.zig");
+const database = @import("database.zig");
 const postgresql = @import("postgresql.zig");
 const _sql = @import("sql.zig");
 const repository = @import("repository.zig");
@@ -118,7 +119,8 @@ pub fn RepositoryInsert(comptime Model: type, comptime TableShape: type, comptim
 		const Configuration = RepositoryInsertConfiguration(InsertShape);
 
 		arena: std.heap.ArenaAllocator,
-		database: *pg.Pool,
+		connector: database.Connector,
+		connection: *database.Connection = undefined,
 		insertConfig: Configuration,
 
 		sql: ?[]const u8 = null,
@@ -289,20 +291,19 @@ pub fn RepositoryInsert(comptime Model: type, comptime TableShape: type, comptim
 		/// Execute the insert query.
 		fn execQuery(self: *Self) !*pg.Result {
 			// Get a connection to the database.
-			const connection = try self.database.acquire();
+			self.connection = try self.connector.getConnection();
-			errdefer connection.release();
+			errdefer self.connection.release();
 
 			// Initialize a new PostgreSQL statement.
-			var statement = try pg.Stmt.init(connection, .{
+			var statement = try pg.Stmt.init(self.connection.connection, .{
 				.column_names = true,
-				.release_conn = true,
 				.allocator = self.arena.allocator(),
 			});
 			errdefer statement.deinit();
 
 			// Prepare SQL insert query.
 			statement.prepare(self.sql.?)
-				catch |err| return postgresql.handlePostgresqlError(err, connection, &statement);
+				catch |err| return postgresql.handlePostgresqlError(err, self.connection, &statement);
 
 			// Bind INSERT query parameters.
 			for (self.insertConfig.values) |row| {
@@ -317,7 +318,7 @@ pub fn RepositoryInsert(comptime Model: type, comptime TableShape: type, comptim
 
 			// Execute the query and get its result.
 			const result = statement.execute()
-				catch |err| return postgresql.handlePostgresqlError(err, connection, &statement);
+				catch |err| return postgresql.handlePostgresqlError(err, self.connection, &statement);
 
 			// Query executed successfully, return the result.
 			return result;
@@ -330,6 +331,7 @@ pub fn RepositoryInsert(comptime Model: type, comptime TableShape: type, comptim
 
 			// Execute query and get its result.
 			var queryResult = try self.execQuery();
+			defer self.connection.release();
 			defer queryResult.deinit();
 
 			//TODO deduplicate this in postgresql.zig, we could do it if Mapper type was exposed.
@@ -359,11 +361,11 @@ pub fn RepositoryInsert(comptime Model: type, comptime TableShape: type, comptim
 		}
 
 		/// Initialize a new repository insert query.
-		pub fn init(allocator: std.mem.Allocator, database: *pg.Pool) Self {
+		pub fn init(allocator: std.mem.Allocator, connector: database.Connector) Self {
 			return .{
 				// Initialize an arena allocator for the insert query.
 				.arena = std.heap.ArenaAllocator.init(allocator),
-				.database = database,
+				.connector = connector,
 				.insertConfig = .{},
 			};
 		}

src/postgresql.zig

@@ -2,6 +2,7 @@ const std = @import("std");
 const pg = @import("pg");
 const global = @import("global.zig");
 const errors = @import("errors.zig");
+const database = @import("database.zig");
 const _sql = @import("sql.zig");
 const repository = @import("repository.zig");
 
@@ -31,11 +32,16 @@ pub fn bindQueryParameter(statement: *pg.Stmt, parameter: _sql.QueryParameter) !
 }
 
 /// PostgreSQL error handling by ZRM.
-pub fn handlePostgresqlError(err: anyerror, connection: *pg.Conn, statement: *pg.Stmt) anyerror {
+pub fn handlePostgresqlError(err: anyerror, connection: *database.Connection, statement: *pg.Stmt) anyerror {
 	// Release connection and statement as query failed.
 	defer statement.deinit();
 	defer connection.release();
 
+	return handleRawPostgresqlError(err, connection.connection);
+}
+
+/// PostgreSQL raw error handling by ZRM.
+pub fn handleRawPostgresqlError(err: anyerror, connection: *pg.Conn) anyerror {
 	if (connection.err) |sqlErr| {
 		if (global.debugMode) {
 			// If debug mode is enabled, show the PostgreSQL error.

src/query.zig

@@ -2,6 +2,7 @@ const std = @import("std");
 const pg = @import("pg");
 const zollections = @import("zollections");
 const errors = @import("errors.zig");
+const database = @import("database.zig");
 const postgresql = @import("postgresql.zig");
 const _sql = @import("sql.zig");
 const conditions = @import("conditions.zig");
@@ -29,7 +30,8 @@ pub fn RepositoryQuery(comptime Model: type, comptime TableShape: type, comptime
 		const Self = @This();
 
 		arena: std.heap.ArenaAllocator,
-		database: *pg.Pool,
+		connector: database.Connector,
+		connection: *database.Connection = undefined,
 		queryConfig: RepositoryQueryConfiguration,
 
 		sql: ?[]const u8 = null,
@@ -176,23 +178,21 @@ pub fn RepositoryQuery(comptime Model: type, comptime TableShape: type, comptime
 		}
 
 		/// Execute the built query.
-		fn execQuery(self: *Self) !*pg.Result
+		fn execQuery(self: *Self) !*pg.Result {
-		{
+			// Get the connection to the database.
-			// Get a connection to the database.
+			self.connection = try self.connector.getConnection();
-			const connection = try self.database.acquire();
+			errdefer self.connection.release();
-			errdefer connection.release();
 
 			// Initialize a new PostgreSQL statement.
-			var statement = try pg.Stmt.init(connection, .{
+			var statement = try pg.Stmt.init(self.connection.connection, .{
 				.column_names = true,
-				.release_conn = true,
 				.allocator = self.arena.allocator(),
 			});
 			errdefer statement.deinit();
 
 			// Prepare SQL query.
 			statement.prepare(self.sql.?)
-				catch |err| return postgresql.handlePostgresqlError(err, connection, &statement);
+				catch |err| return postgresql.handlePostgresqlError(err, self.connection, &statement);
 
 			// Bind query parameters.
 			if (self.queryConfig.select) |_select|
@@ -204,7 +204,7 @@ pub fn RepositoryQuery(comptime Model: type, comptime TableShape: type, comptime
 
 			// Execute the query and get its result.
 			const result = statement.execute()
-				catch |err| return postgresql.handlePostgresqlError(err, connection, &statement);
+				catch |err| return postgresql.handlePostgresqlError(err, self.connection, &statement);
 
 			// Query executed successfully, return the result.
 			return result;
@@ -217,6 +217,7 @@ pub fn RepositoryQuery(comptime Model: type, comptime TableShape: type, comptime
 
 			// Execute query and get its result.
 			var queryResult = try self.execQuery();
+			defer self.connection.release();
 			defer queryResult.deinit();
 
 			//TODO deduplicate this in postgresql.zig, we could do it if Mapper type was exposed.
@@ -246,17 +247,18 @@ pub fn RepositoryQuery(comptime Model: type, comptime TableShape: type, comptime
 		}
 
 		/// Initialize a new repository query.
-		pub fn init(allocator: std.mem.Allocator, database: *pg.Pool, queryConfig: RepositoryQueryConfiguration) Self {
+		pub fn init(allocator: std.mem.Allocator, connector: database.Connector, queryConfig: RepositoryQueryConfiguration) Self {
 			return .{
 				// Initialize the query arena allocator.
 				.arena = std.heap.ArenaAllocator.init(allocator),
-				.database = database,
+				.connector = connector,
 				.queryConfig = queryConfig,
 			};
 		}
 
 		/// Deinitialize the repository query.
 		pub fn deinit(self: *Self) void {
+			// Free everything allocated for this query.
 			self.arena.deinit();
 		}
 	};

src/repository.zig

@@ -1,6 +1,6 @@
 const std = @import("std");
-const pg = @import("pg");
 const zollections = @import("zollections");
+const database = @import("database.zig");
 const _sql = @import("sql.zig");
 const _conditions = @import("conditions.zig");
 const query = @import("query.zig");
@@ -97,9 +97,9 @@ pub fn Repository(comptime Model: type, comptime TableShape: type, comptime conf
 		/// modelKey can be an array / slice of keys.
 		/// For composite keys: modelKey must be a struct with all the keys, matching the type of their corresponding field.
 		/// modelKey can be an array / slice of these structs.
-		pub fn find(allocator: std.mem.Allocator, database: *pg.Pool, modelKey: anytype) !RepositoryResult(Model) {
+		pub fn find(allocator: std.mem.Allocator, connector: database.Connector, modelKey: anytype) !RepositoryResult(Model) {
 			// Initialize a new query.
-			var modelQuery = Self.Query.init(allocator, database, .{});
+			var modelQuery = Self.Query.init(allocator, connector, .{});
 			defer modelQuery.deinit();
 
 			if (config.key.len == 1) {
@@ -114,13 +114,27 @@ pub fn Repository(comptime Model: type, comptime TableShape: type, comptime conf
 							.One => {
 								switch (@typeInfo(ptr.child)) {
 									// Add a whereIn with the array.
-									.Array => try modelQuery.whereIn(keyType, keyName, modelKey),
+									.Array => {
+										if (ptr.child == u8)
+											// If the child is a string, use it as a simple value.
+											try modelQuery.whereValue(KeyType, keyName, "=", modelKey)
+										else
+											// Otherwise, use it as an array.
+											try modelQuery.whereIn(keyType, keyName, modelKey);
+									},
 									// Add a simple condition with the pointed value.
 									else => try modelQuery.whereValue(keyType, keyName, "=", modelKey.*),
 								}
 							},
 							// Add a whereIn with the slice.
-							else => try modelQuery.whereIn(keyType, keyName, modelKey),
+							else => {
+								if (ptr.child == u8)
+									// If the child is a string, use it as a simple value.
+									try modelQuery.whereValue(KeyType, keyName, "=", modelKey)
+								else
+									// Otherwise, use it as an array.
+									try modelQuery.whereIn(keyType, keyName, modelKey);
+							},
 						}
 					},
 					// Add a simple condition with the given value.
@@ -165,9 +179,9 @@ pub fn Repository(comptime Model: type, comptime TableShape: type, comptime conf
 
 		/// Perform creation of the given new model in the repository.
 		/// The model will be altered with the inserted values.
-		pub fn create(allocator: std.mem.Allocator, database: *pg.Pool, newModel: *Model) !RepositoryResult(Model) {
+		pub fn create(allocator: std.mem.Allocator, connector: database.Connector, newModel: *Model) !RepositoryResult(Model) {
 			// Initialize a new insert query for the given model.
-			var insertQuery = Self.Insert.init(allocator, database);
+			var insertQuery = Self.Insert.init(allocator, connector);
 			defer insertQuery.deinit();
 			try insertQuery.values(newModel);
 			insertQuery.returningAll();
@@ -185,12 +199,12 @@ pub fn Repository(comptime Model: type, comptime TableShape: type, comptime conf
 		}
 
 		/// Perform save of the given existing model in the repository.
-		pub fn save(allocator: std.mem.Allocator, database: *pg.Pool, existingModel: *Model) !RepositoryResult(Model) {
+		pub fn save(allocator: std.mem.Allocator, connector: database.Connector, existingModel: *Model) !RepositoryResult(Model) {
 			// Convert the model to its SQL form.
 			const modelSql = try config.toSql(existingModel.*);
 
 			// Initialize a new update query for the given model.
-			var updateQuery = Self.Update(TableShape).init(allocator, database);
+			var updateQuery = Self.Update(TableShape).init(allocator, connector);
 			defer updateQuery.deinit();
 			try updateQuery.set(modelSql);
 			updateQuery.returningAll();

src/root.zig

@@ -1,4 +1,5 @@
 const global = @import("global.zig");
+const session = @import("session.zig");
 const repository = @import("repository.zig");
 const insert = @import("insert.zig");
 const _sql = @import("sql.zig");
@@ -14,6 +15,9 @@ pub const Insertable = insert.Insertable;
 pub const QueryParameter = _sql.QueryParameter;
 pub const SqlParams = _sql.SqlParams;
 
+pub const database = @import("database.zig");
+pub const Session = session.Session;
+
 pub const conditions = @import("conditions.zig");
 
 pub const errors = @import("errors.zig");

src/session.zig

@@ -0,0 +1,122 @@
+const std = @import("std");
+const pg = @import("pg");
+const postgresql = @import("postgresql.zig");
+const database = @import("database.zig");
+
+/// Session for multiple repository operations.
+pub const Session = struct {
+	const Self = @This();
+
+	_database: *pg.Pool,
+
+	/// The active connection for the session.
+	connection: *pg.Conn,
+
+	/// Execute a comptime-known SQL command for the current session.
+	fn exec(self: Self, comptime sql: []const u8) !void {
+		_ = self.connection.exec(sql, .{}) catch |err| {
+			return postgresql.handleRawPostgresqlError(err, self.connection);
+		};
+	}
+
+	/// Begin a new transaction.
+	pub fn beginTransaction(self: Self) !void {
+		try self.exec("BEGIN;");
+	}
+
+	/// Rollback the current transaction.
+	pub fn rollbackTransaction(self: Self) !void {
+		try self.exec("ROLLBACK;");
+	}
+
+	/// Commit the current transaction.
+	pub fn commitTransaction(self: Self) !void {
+		try self.exec("COMMIT;");
+	}
+
+	/// Create a new savepoint with the given name.
+	pub fn savepoint(self: Self, comptime _savepoint: []const u8) !void {
+		try self.exec("SAVEPOINT " ++ _savepoint ++ ";");
+	}
+
+	/// Rollback to the savepoint with the given name.
+	pub fn rollbackTo(self: Self, comptime _savepoint: []const u8) !void {
+		try self.exec("ROLLBACK TO " ++ _savepoint ++ ";");
+	}
+
+	/// Initialize a new session.
+	pub fn init(_database: *pg.Pool) !Session {
+		return .{
+			._database = _database,
+			.connection = try _database.acquire(),
+		};
+	}
+
+	/// Deinitialize the session.
+	pub fn deinit(self: *Self) void {
+		self.connection.release();
+	}
+
+	/// Get a database connector instance for the current session.
+	pub fn connector(self: *Self) database.Connector {
+		return database.Connector{
+			._interface = .{
+				.instance = self,
+				.getConnection = getConnection,
+			},
+		};
+	}
+
+	// Connector implementation.
+
+	/// Get the current connection.
+	fn getConnection(opaqueSelf: *anyopaque) !*database.Connection {
+		const self: *Self = @ptrCast(@alignCast(opaqueSelf));
+
+		// Initialize a new connection.
+		const sessionConnection = try self._database._allocator.create(SessionConnection);
+		sessionConnection.* = .{
+			.session = self,
+		};
+
+		return try sessionConnection.connection();
+	}
+};
+
+fn noRelease(_: *anyopaque) void {}
+
+/// A session connection.
+const SessionConnection = struct {
+	const Self = @This();
+
+	/// Session of the connection.
+	session: *Session,
+
+	/// Connection instance, to only keep one at a time.
+	_connection: ?database.Connection = null,
+
+	/// Get a database connection.
+	pub fn connection(self: *Self) !*database.Connection {
+		if (self._connection == null) {
+			// A new connection needs to be initialized.
+			self._connection = .{
+				.connection = self.session.connection,
+				._interface = .{
+					.instance = self,
+					.release = releaseConnection,
+				},
+			};
+		}
+
+		return &(self._connection.?);
+	}
+
+	// Implementation.
+
+	/// Free the current connection (doesn't actually release the connection, as it is required to stay the same all along the session).
+	fn releaseConnection(self: *database.Connection) void {
+		// Free allocated connection.
+		const sessionConnection: *SessionConnection = @ptrCast(@alignCast(self._interface.instance));
+		sessionConnection.session._database._allocator.destroy(sessionConnection);
+	}
+};

src/update.zig

@@ -2,6 +2,7 @@ const std = @import("std");
 const pg = @import("pg");
 const zollections = @import("zollections");
 const errors = @import("errors.zig");
+const database = @import("database.zig");
 const postgresql = @import("postgresql.zig");
 const _sql = @import("sql.zig");
 const conditions = @import("conditions.zig");
@@ -57,7 +58,8 @@ pub fn RepositoryUpdate(comptime Model: type, comptime TableShape: type, comptim
 		const Configuration = RepositoryUpdateConfiguration(UpdateShape);
 
 		arena: std.heap.ArenaAllocator,
-		database: *pg.Pool,
+		connector: database.Connector,
+		connection: *database.Connection = undefined,
 		updateConfig: Configuration,
 
 		sql: ?[]const u8 = null,
@@ -261,20 +263,19 @@ pub fn RepositoryUpdate(comptime Model: type, comptime TableShape: type, comptim
 		/// Execute the update query.
 		fn execQuery(self: *Self) !*pg.Result {
 			// Get a connection to the database.
-			const connection = try self.database.acquire();
+			self.connection = try self.connector.getConnection();
-			errdefer connection.release();
+			errdefer self.connection.release();
 
 			// Initialize a new PostgreSQL statement.
-			var statement = try pg.Stmt.init(connection, .{
+			var statement = try pg.Stmt.init(self.connection.connection, .{
 				.column_names = true,
-				.release_conn = true,
 				.allocator = self.arena.allocator(),
 			});
 			errdefer statement.deinit();
 
 			// Prepare SQL update query.
 			statement.prepare(self.sql.?)
-				catch |err| return postgresql.handlePostgresqlError(err, connection, &statement);
+				catch |err| return postgresql.handlePostgresqlError(err, self.connection, &statement);
 
 			// Bind UPDATE query parameters.
 			inline for (columns) |column| {
@@ -291,7 +292,7 @@ pub fn RepositoryUpdate(comptime Model: type, comptime TableShape: type, comptim
 
 			// Execute the query and get its result.
 			const result = statement.execute()
-				catch |err| return postgresql.handlePostgresqlError(err, connection, &statement);
+				catch |err| return postgresql.handlePostgresqlError(err, self.connection, &statement);
 
 			// Query executed successfully, return the result.
 			return result;
@@ -304,6 +305,7 @@ pub fn RepositoryUpdate(comptime Model: type, comptime TableShape: type, comptim
 
 			// Execute query and get its result.
 			var queryResult = try self.execQuery();
+			defer self.connection.release();
 			defer queryResult.deinit();
 
 			//TODO deduplicate this in postgresql.zig, we could do it if Mapper type was exposed.
@@ -333,11 +335,11 @@ pub fn RepositoryUpdate(comptime Model: type, comptime TableShape: type, comptim
 		}
 
 		/// Initialize a new repository update query.
-		pub fn init(allocator: std.mem.Allocator, database: *pg.Pool) Self {
+		pub fn init(allocator: std.mem.Allocator, connector: database.Connector) Self {
 			return .{
 				// Initialize an arena allocator for the update query.
 				.arena = std.heap.ArenaAllocator.init(allocator),
-				.database = database,
+				.connector = connector,
 				.updateConfig = .{},
 			};
 		}

tests/composite.zig

@@ -17,6 +17,7 @@ fn initDatabase() !void {
 			.password = "zrm",
 			.database = "zrm",
 		},
+		.size = 1,
 	});
 }
 
@@ -76,6 +77,9 @@ test "composite model create, save and find" {
 
 	try initDatabase();
 	defer database.deinit();
+	var poolConnector = zrm.database.PoolConnector{
+		.pool = database,
+	};
 
 	// Initialize a test model.
 	var newModel = CompositeModel{
@@ -86,7 +90,7 @@ test "composite model create, save and find" {
 
 
 	// Create the new model.
-	var result = try CompositeModelRepository.create(std.testing.allocator, database, &newModel);
+	var result = try CompositeModelRepository.create(std.testing.allocator, poolConnector.connector(), &newModel);
 	defer result.deinit(); // Will clear some values in newModel.
 
 	// Check that the model is correctly defined.
@@ -101,7 +105,7 @@ test "composite model create, save and find" {
 	// Update the model.
 	newModel.label = null;
 
-	var result2 = try CompositeModelRepository.save(std.testing.allocator, database, &newModel);
+	var result2 = try CompositeModelRepository.save(std.testing.allocator, poolConnector.connector(), &newModel);
 	defer result2.deinit(); // Will clear some values in newModel.
 
 	// Checking that the model has been updated (but only the right field).
@@ -111,7 +115,7 @@ test "composite model create, save and find" {
 
 
 	// Do another insert with the same secondcol.
-	var insertQuery = CompositeModelRepository.Insert.init(std.testing.allocator, database);
+	var insertQuery = CompositeModelRepository.Insert.init(std.testing.allocator, poolConnector.connector());
 	defer insertQuery.deinit();
 	try insertQuery.values(.{
 		.secondcol = "identifier",
@@ -128,7 +132,7 @@ test "composite model create, save and find" {
 
 
 	// Try to find the created then saved model, to check that everything has been saved correctly.
-	var result4 = try CompositeModelRepository.find(std.testing.allocator, database, .{
+	var result4 = try CompositeModelRepository.find(std.testing.allocator, poolConnector.connector(), .{
 		.firstcol = newModel.firstcol,
 		.secondcol = newModel.secondcol,
 	});
@@ -139,7 +143,7 @@ test "composite model create, save and find" {
 
 
 	// Try to find multiple models at once.
-	var result5 = try CompositeModelRepository.find(std.testing.allocator, database, &[_]CompositeModelRepository.KeyType{
+	var result5 = try CompositeModelRepository.find(std.testing.allocator, poolConnector.connector(), &[_]CompositeModelRepository.KeyType{
 		.{
 			.firstcol = newModel.firstcol,
 			.secondcol = newModel.secondcol,

tests/initdb.sql

@@ -11,6 +11,7 @@ CREATE TABLE models (
 
 -- Insert default data.
 INSERT INTO models(name, amount) VALUES ('test', 50);
+INSERT INTO models(name, amount) VALUES ('updatable', 33.12);
 
 -- Create default composite models table.
 CREATE TABLE composite_models (

tests/repository.zig

@@ -17,6 +17,7 @@ fn initDatabase() !void {
 			.password = "zrm",
 			.database = "zrm",
 		},
+		.size = 1,
 	});
 }
 
@@ -29,7 +30,7 @@ const MySubmodel = struct {
 };
 
 /// An example model.
-const MyModel = struct {
+pub const MyModel = struct {
 	id: i32,
 	name: []const u8,
 	amount: f64,
@@ -38,7 +39,7 @@ const MyModel = struct {
 };
 
 /// SQL table shape of the example model.
-const MyModelTable = struct {
+pub const MyModelTable = struct {
 	id: i32,
 	name: []const u8,
 	amount: f64,
@@ -63,7 +64,7 @@ fn modelToSql(model: MyModel) !MyModelTable {
 }
 
 /// Declare a model repository.
-const MyModelRepository = zrm.Repository(MyModel, MyModelTable, .{
+pub const MyModelRepository = zrm.Repository(MyModel, MyModelTable, .{
 	.table = "models",
 
 	// Insert shape used by default for inserts in the repository.
@@ -105,8 +106,11 @@ test "repository query SQL builder" {
 
 	try initDatabase();
 	defer database.deinit();
+	var poolConnector = zrm.database.PoolConnector{
+		.pool = database,
+	};
 
-	var query = MyModelRepository.Query.init(std.testing.allocator, database, .{});
+	var query = MyModelRepository.Query.init(std.testing.allocator, poolConnector.connector(), .{});
 	defer query.deinit();
 	try query.whereIn(usize, "id", &[_]usize{1, 2});
 	try query.buildSql();
@@ -121,9 +125,12 @@ test "repository element retrieval" {
 
 	try initDatabase();
 	defer database.deinit();
+	var poolConnector = zrm.database.PoolConnector{
+		.pool = database,
+	};
 
 	// Prepare a query for models.
-	var query = MyModelRepository.Query.init(std.testing.allocator, database, .{});
+	var query = MyModelRepository.Query.init(std.testing.allocator, poolConnector.connector(), .{});
 	try query.whereValue(usize, "id", "=", 1);
 	defer query.deinit();
 
@@ -152,8 +159,11 @@ test "repository complex SQL query" {
 
 	try initDatabase();
 	defer database.deinit();
+	var poolConnector = zrm.database.PoolConnector{
+		.pool = database,
+	};
 
-	var query = MyModelRepository.Query.init(std.testing.allocator, database, .{});
+	var query = MyModelRepository.Query.init(std.testing.allocator, poolConnector.connector(), .{});
 	defer query.deinit();
 	query.where(
 		try query.newCondition().@"or"(&[_]zrm.SqlParams{
@@ -187,6 +197,9 @@ test "repository element creation" {
 
 	try initDatabase();
 	defer database.deinit();
+	var poolConnector = zrm.database.PoolConnector{
+		.pool = database,
+	};
 
 	// Create a model to insert.
 	const newModel = MyModel{
@@ -196,7 +209,7 @@ test "repository element creation" {
 	};
 
 	// Initialize an insert query.
-	var insertQuery = MyModelRepository.Insert.init(std.testing.allocator, database);
+	var insertQuery = MyModelRepository.Insert.init(std.testing.allocator, poolConnector.connector());
 	defer insertQuery.deinit();
 	// Insert the new model.
 	try insertQuery.values(newModel);
@@ -225,16 +238,19 @@ test "repository element update" {
 
 	try initDatabase();
 	defer database.deinit();
+	var poolConnector = zrm.database.PoolConnector{
+		.pool = database,
+	};
 
 	// Initialize an update query.
 	var updateQuery = MyModelRepository.Update(struct {
 		name: []const u8,
-	}).init(std.testing.allocator, database);
+	}).init(std.testing.allocator, poolConnector.connector());
 	defer updateQuery.deinit();
 
 	// Update a model's name.
 	try updateQuery.set(.{ .name = "newname" });
-	try updateQuery.whereValue(usize, "id", "=", 1);
+	try updateQuery.whereValue(usize, "id", "=", 2);
 	updateQuery.returningAll();
 
 	// Build SQL.
@@ -251,7 +267,7 @@ test "repository element update" {
 
 	// Check the updated model.
 	try std.testing.expectEqual(1, result.models.len);
-	try std.testing.expectEqual(1, result.models[0].id);
+	try std.testing.expectEqual(2, result.models[0].id);
 	try std.testing.expectEqualStrings("newname", result.models[0].name);
 }
 
@@ -260,6 +276,9 @@ test "model create, save and find" {
 
 	try initDatabase();
 	defer database.deinit();
+	var poolConnector = zrm.database.PoolConnector{
+		.pool = database,
+	};
 
 	// Initialize a test model.
 	var newModel = MyModel{
@@ -270,7 +289,7 @@ test "model create, save and find" {
 
 
 	// Create the new model.
-	var result = try MyModelRepository.create(std.testing.allocator, database, &newModel);
+	var result = try MyModelRepository.create(std.testing.allocator, poolConnector.connector(), &newModel);
 	defer result.deinit(); // Will clear some values in newModel.
 
 	// Check that the model is correctly defined.
@@ -284,7 +303,7 @@ test "model create, save and find" {
 	// Update the model.
 	newModel.name = "recently updated name";
 
-	var result2 = try MyModelRepository.save(std.testing.allocator, database, &newModel);
+	var result2 = try MyModelRepository.save(std.testing.allocator, poolConnector.connector(), &newModel);
 	defer result2.deinit(); // Will clear some values in newModel.
 
 	// Checking that the model has been updated (but only the right field).
@@ -296,7 +315,7 @@ test "model create, save and find" {
 	// Do another update.
 	newModel.amount = 12.226;
 
-	var result3 = try MyModelRepository.save(std.testing.allocator, database, &newModel);
+	var result3 = try MyModelRepository.save(std.testing.allocator, poolConnector.connector(), &newModel);
 	defer result3.deinit(); // Will clear some values in newModel.
 
 	// Checking that the model has been updated (but only the right field).
@@ -306,14 +325,14 @@ test "model create, save and find" {
 
 
 	// Try to find the created then saved model, to check that everything has been saved correctly.
-	var result4 = try MyModelRepository.find(std.testing.allocator, database, newModel.id);
+	var result4 = try MyModelRepository.find(std.testing.allocator, poolConnector.connector(), newModel.id);
 	defer result4.deinit(); // Will clear some values in newModel.
 
 	try std.testing.expectEqualDeep(newModel, result4.first().?.*);
 
 
 	// Try to find multiple models at once.
-	var result5 = try MyModelRepository.find(std.testing.allocator, database, &[_]i32{1, newModel.id});
+	var result5 = try MyModelRepository.find(std.testing.allocator, poolConnector.connector(), &[_]i32{1, newModel.id});
 	defer result5.deinit();
 
 	try std.testing.expectEqual(2, result5.models.len);

tests/root.zig

@@ -4,4 +4,5 @@ comptime {
 	_ = @import("query.zig");
 	_ = @import("repository.zig");
 	_ = @import("composite.zig");
+	_ = @import("sessions.zig");
 }

tests/sessions.zig

@@ -0,0 +1,134 @@
+const std = @import("std");
+const pg = @import("pg");
+const zrm = @import("zrm");
+const repository = @import("repository.zig");
+
+/// PostgreSQL database connection.
+var database: *pg.Pool = undefined;
+
+/// Initialize database connection.
+fn initDatabase(allocator: std.mem.Allocator) !void {
+	database = try pg.Pool.init(allocator, .{
+		.connect = .{
+			.host = "localhost",
+			.port = 5432,
+		},
+		.auth = .{
+			.username = "zrm",
+			.password = "zrm",
+			.database = "zrm",
+		},
+		.size = 1,
+	});
+}
+
+test "session with rolled back transaction and savepoint" {
+	zrm.setDebug(true);
+
+	// Initialize database.
+	try initDatabase(std.testing.allocator);
+	defer database.deinit();
+
+	// Start a new session and perform operations in a transaction.
+	var session = try zrm.Session.init(database);
+	defer session.deinit();
+
+
+	try session.beginTransaction();
+
+	
+	// First UPDATE in the transaction.
+	{
+		var firstUpdate = repository.MyModelRepository.Update(struct {
+			name: []const u8,
+		}).init(std.testing.allocator, session.connector());
+		defer firstUpdate.deinit();
+		try firstUpdate.set(.{
+			.name = "tempname",
+		});
+		try firstUpdate.whereValue(usize, "id", "=", 1);
+		var firstUpdateResult = try firstUpdate.update(std.testing.allocator);
+		firstUpdateResult.deinit();
+	}
+
+
+	// Set a savepoint.
+	try session.savepoint("my_savepoint");
+
+
+	// Second UPDATE in the transaction.
+	{
+		var secondUpdate = repository.MyModelRepository.Update(struct {
+			amount: f64,
+		}).init(std.testing.allocator, session.connector());
+		defer secondUpdate.deinit();
+		try secondUpdate.set(.{
+			.amount = 52.25,
+		});
+		try secondUpdate.whereValue(usize, "id", "=", 1);
+		var secondUpdateResult = try secondUpdate.update(std.testing.allocator);
+		secondUpdateResult.deinit();
+	}
+
+	// SELECT before rollback to savepoint in the transaction.
+	{
+		var queryBeforeRollbackToSavepoint = repository.MyModelRepository.Query.init(std.testing.allocator, session.connector(), .{});
+		try queryBeforeRollbackToSavepoint.whereValue(usize, "id", "=", 1);
+		defer queryBeforeRollbackToSavepoint.deinit();
+
+		// Get models.
+		var resultBeforeRollbackToSavepoint = try queryBeforeRollbackToSavepoint.get(std.testing.allocator);
+		defer resultBeforeRollbackToSavepoint.deinit();
+
+		// Check that one model has been retrieved, then check its type and values.
+		try std.testing.expectEqual(1, resultBeforeRollbackToSavepoint.models.len);
+		try std.testing.expectEqual(repository.MyModel, @TypeOf(resultBeforeRollbackToSavepoint.models[0].*));
+		try std.testing.expectEqual(1, resultBeforeRollbackToSavepoint.models[0].id);
+		try std.testing.expectEqualStrings("tempname", resultBeforeRollbackToSavepoint.models[0].name);
+		try std.testing.expectEqual(52.25, resultBeforeRollbackToSavepoint.models[0].amount);
+	}
+
+
+	try session.rollbackTo("my_savepoint");
+
+
+	// SELECT after rollback to savepoint in the transaction.
+	{
+		var queryAfterRollbackToSavepoint = repository.MyModelRepository.Query.init(std.testing.allocator, session.connector(), .{});
+		try queryAfterRollbackToSavepoint.whereValue(usize, "id", "=", 1);
+		defer queryAfterRollbackToSavepoint.deinit();
+
+		// Get models.
+		var resultAfterRollbackToSavepoint = try queryAfterRollbackToSavepoint.get(std.testing.allocator);
+		defer resultAfterRollbackToSavepoint.deinit();
+
+		// Check that one model has been retrieved, then check its type and values.
+		try std.testing.expectEqual(1, resultAfterRollbackToSavepoint.models.len);
+		try std.testing.expectEqual(repository.MyModel, @TypeOf(resultAfterRollbackToSavepoint.models[0].*));
+		try std.testing.expectEqual(1, resultAfterRollbackToSavepoint.models[0].id);
+		try std.testing.expectEqualStrings("tempname", resultAfterRollbackToSavepoint.models[0].name);
+		try std.testing.expectEqual(50.00, resultAfterRollbackToSavepoint.models[0].amount);
+	}
+
+
+	try session.rollbackTransaction();
+
+
+	// SELECT outside of the rolled back transaction.
+	{
+		var queryOutside = repository.MyModelRepository.Query.init(std.testing.allocator, session.connector(), .{});
+		try queryOutside.whereValue(usize, "id", "=", 1);
+		defer queryOutside.deinit();
+
+		// Get models.
+		var resultOutside = try queryOutside.get(std.testing.allocator);
+		defer resultOutside.deinit();
+
+		// Check that one model has been retrieved, then check its type and values.
+		try std.testing.expectEqual(1, resultOutside.models.len);
+		try std.testing.expectEqual(repository.MyModel, @TypeOf(resultOutside.models[0].*));
+		try std.testing.expectEqual(1, resultOutside.models[0].id);
+		try std.testing.expectEqualStrings("test", resultOutside.models[0].name);
+		try std.testing.expectEqual(50.00, resultOutside.models[0].amount);
+	}
+}