Add transaction model aiopg (#219)

* #197 Add transaction model aiopg

* add docs

Author: vir-mir

aiopg/__init__.py

@@ -5,16 +5,16 @@
 from .connection import connect, Connection, TIMEOUT as DEFAULT_TIMEOUT
 from .cursor import Cursor
 from .pool import create_pool, Pool
-
+from .transaction import IsolationLevel, Transaction
 
 __all__ = ('connect', 'create_pool', 'Connection', 'Cursor', 'Pool',
-           'version', 'version_info', 'DEFAULT_TIMEOUT')
+           'version', 'version_info', 'DEFAULT_TIMEOUT', 'IsolationLevel',
+           'Transaction')
 
 __version__ = '0.13.1'
 
 version = __version__ + ' , Python ' + sys.version
 
-
 VersionInfo = namedtuple('VersionInfo',
                          'major minor micro releaselevel serial')
 
@@ -40,6 +40,6 @@ def _parse_version(ver):
 
 version_info = _parse_version(__version__)
 
-
 # make pyflakes happy
-(connect, create_pool, Connection, Cursor, Pool, DEFAULT_TIMEOUT)
+(connect, create_pool, Connection, Cursor, Pool, DEFAULT_TIMEOUT,
+ IsolationLevel, Transaction)

aiopg/cursor.py

@@ -4,16 +4,17 @@
 import psycopg2
 
 from .log import logger
-from .utils import PY_35, PY_352
+from .transaction import Transaction, IsolationLevel
+from .utils import PY_35, PY_352, _TransactionBeginContextManager
 
 
 class Cursor:
-
     def __init__(self, conn, impl, timeout, echo):
         self._conn = conn
         self._impl = impl
         self._timeout = timeout
         self._echo = echo
+        self._transaction = Transaction(self, IsolationLevel.repeatable_read)
 
     @property
     def echo(self):
@@ -146,6 +147,16 @@ def callproc(self, procname, parameters=None, *, timeout=None):
         else:
             yield from self._conn._poll(waiter, timeout)
 
+    def begin(self):
+        return _TransactionBeginContextManager(self._transaction.begin())
+
+    def begin_nested(self):
+        if not self._transaction.is_begin:
+            return _TransactionBeginContextManager(
+                self._transaction.begin())
+        else:
+            return self._transaction.point()
+
     @asyncio.coroutine
     def mogrify(self, operation, parameters=None):
         """Return a query string after arguments binding.

aiopg/transaction.py

@@ -0,0 +1,191 @@
+import asyncio
+import enum
+import uuid
+import warnings
+from abc import ABC, abstractmethod
+
+import psycopg2
+from aiopg.utils import PY_35, _TransactionPointContextManager
+
+__all__ = ('IsolationLevel', 'Transaction')
+
+
+class IsolationCompiler(ABC):
+    name = ''
+
+    __slots__ = ('_readonly', '_deferrable')
+
+    def __init__(self, readonly, deferrable):
+        self._readonly = readonly
+        self._deferrable = deferrable
+        self._check_readonly_deferrable()
+
+    def _check_readonly_deferrable(self):
+        available = self._readonly or self._deferrable
+        if not isinstance(self, SerializableCompiler) and available:
+            raise ValueError('Is only available for serializable transactions')
+
+    def savepoint(self, unique_id):
+        return 'SAVEPOINT {}'.format(unique_id)
+
+    def release_savepoint(self, unique_id):
+        return 'RELEASE SAVEPOINT {}'.format(unique_id)
+
+    def rollback_savepoint(self, unique_id):
+        return 'ROLLBACK TO SAVEPOINT {}'.format(unique_id)
+
+    def commit(self):
+        return 'COMMIT'
+
+    def rollback(self):
+        return 'ROLLBACK'
+
+    @abstractmethod
+    def begin(self):
+        raise NotImplementedError("Please Implement this method")
+
+    def __repr__(self):
+        return self.name
+
+
+class ReadCommittedCompiler(IsolationCompiler):
+    name = 'Read committed'
+
+    def begin(self):
+        return 'BEGIN'
+
+
+class RepeatableReadCompiler(IsolationCompiler):
+    name = 'Repeatable read'
+
+    def begin(self):
+        return 'BEGIN ISOLATION LEVEL REPEATABLE READ'
+
+
+class SerializableCompiler(IsolationCompiler):
+    name = 'Serializable'
+
+    def begin(self):
+        query = 'BEGIN ISOLATION LEVEL SERIALIZABLE'
+
+        if self._readonly:
+            query += ' READ ONLY'
+
+        if self._deferrable:
+            query += ' DEFERRABLE'
+
+        return query
+
+
+class IsolationLevel(enum.Enum):
+    serializable = SerializableCompiler
+    repeatable_read = RepeatableReadCompiler
+    read_committed = ReadCommittedCompiler
+
+    def __call__(self, readonly, deferrable):
+        return self.value(readonly, deferrable)
+
+
+class Transaction:
+    __slots__ = ('_cur', '_is_begin', '_isolation', '_unique_id')
+
+    def __init__(self, cur, isolation_level,
+                 readonly=False, deferrable=False):
+        self._cur = cur
+        self._is_begin = False
+        self._unique_id = None
+        self._isolation = isolation_level(readonly, deferrable)
+
+    @property
+    def is_begin(self):
+        return self._is_begin
+
+    @asyncio.coroutine
+    def begin(self):
+        if self._is_begin:
+            raise psycopg2.ProgrammingError(
+                'You are trying to open a new transaction, use the save point')
+        self._is_begin = True
+        yield from self._cur.execute(self._isolation.begin())
+        return self
+
+    @asyncio.coroutine
+    def commit(self):
+        self._check_commit_rollback()
+        yield from self._cur.execute(self._isolation.commit())
+        self._is_begin = False
+
+    @asyncio.coroutine
+    def rollback(self):
+        self._check_commit_rollback()
+        yield from self._cur.execute(self._isolation.rollback())
+        self._is_begin = False
+
+    @asyncio.coroutine
+    def rollback_savepoint(self):
+        self._check_release_rollback()
+        yield from self._cur.execute(
+            self._isolation.rollback_savepoint(self._unique_id))
+        self._unique_id = None
+
+    @asyncio.coroutine
+    def release_savepoint(self):
+        self._check_release_rollback()
+        yield from self._cur.execute(
+            self._isolation.release_savepoint(self._unique_id))
+        self._unique_id = None
+
+    @asyncio.coroutine
+    def savepoint(self):
+        self._check_commit_rollback()
+        if self._unique_id is not None:
+            raise psycopg2.ProgrammingError('You do not shut down savepoint')
+
+        self._unique_id = 's{}'.format(uuid.uuid1().hex)
+        yield from self._cur.execute(
+            self._isolation.savepoint(self._unique_id))
+
+        return self
+
+    def point(self):
+        return _TransactionPointContextManager(self.savepoint())
+
+    def _check_commit_rollback(self):
+        if not self._is_begin:
+            raise psycopg2.ProgrammingError('You are trying to commit '
+                                            'the transaction does not open')
+
+    def _check_release_rollback(self):
+        self._check_commit_rollback()
+        if self._unique_id is None:
+            raise psycopg2.ProgrammingError('You do not start savepoint')
+
+    def __repr__(self):
+        return "<{} transaction={} id={:#x}>".format(
+            self.__class__.__name__,
+            self._isolation,
+            id(self)
+        )
+
+    def __del__(self):
+        if self._is_begin:
+            warnings.warn(
+                "You have not closed transaction {!r}".format(self),
+                ResourceWarning)
+
+        if self._unique_id is not None:
+            warnings.warn(
+                "You have not closed savepoint {!r}".format(self),
+                ResourceWarning)
+
+    if PY_35:
+        @asyncio.coroutine
+        def __aenter__(self):
+            return (yield from self.begin())
+
+        @asyncio.coroutine
+        def __aexit__(self, exc_type, exc, tb):
+            if exc_type is not None:
+                yield from self.rollback()
+            else:
+                yield from self.commit()

aiopg/utils.py

@@ -1,17 +1,16 @@
 import asyncio
 import sys
 
-
 PY_35 = sys.version_info >= (3, 5)
 PY_352 = sys.version_info >= (3, 5, 2)
 
 if PY_35:
     from collections.abc import Coroutine
+
     base = Coroutine
 else:
     base = object
 
-
 try:
     ensure_future = asyncio.ensure_future
 except AttributeError:
@@ -26,7 +25,6 @@ def create_future(loop):
 
 
 class _ContextManager(base):
-
     __slots__ = ('_coro', '_obj')
 
     def __init__(self, coro):
@@ -84,7 +82,6 @@ def __aexit__(self, exc_type, exc, tb):
 
 
 class _SAConnectionContextManager(_ContextManager):
-
     if PY_35:  # pragma: no branch
         if PY_352:
             def __aiter__(self):
@@ -97,7 +94,6 @@ def __aiter__(self):
 
 
 class _PoolContextManager(_ContextManager):
-
     if PY_35:
         @asyncio.coroutine
         def __aexit__(self, exc_type, exc, tb):
@@ -106,8 +102,33 @@ def __aexit__(self, exc_type, exc, tb):
             self._obj = None
 
 
-class _TransactionContextManager(_ContextManager):
+class _TransactionPointContextManager(_ContextManager):
+    if PY_35:
+
+        @asyncio.coroutine
+        def __aexit__(self, exc_type, exc_val, exc_tb):
+            if exc_type is not None:
+                yield from self._obj.rollback_savepoint()
+            else:
+                yield from self._obj.release_savepoint()
+
+            self._obj = None
 
+
+class _TransactionBeginContextManager(_ContextManager):
+    if PY_35:
+
+        @asyncio.coroutine
+        def __aexit__(self, exc_type, exc_val, exc_tb):
+            if exc_type is not None:
+                yield from self._obj.rollback()
+            else:
+                yield from self._obj.commit()
+
+            self._obj = None
+
+
+class _TransactionContextManager(_ContextManager):
     if PY_35:
 
         @asyncio.coroutine
@@ -121,7 +142,6 @@ def __aexit__(self, exc_type, exc, tb):
 
 
 class _PoolAcquireContextManager(_ContextManager):
-
     __slots__ = ('_coro', '_conn', '_pool')
 
     def __init__(self, coro, pool):
@@ -228,6 +248,7 @@ def __exit__(self, *args):
 if not PY_35:
     try:
         from asyncio import coroutines
+
         coroutines._COROUTINE_TYPES += (_ContextManager,)
     except:
         pass