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This commit is contained in:
Ruud
2012-02-11 16:28:06 +01:00
parent 3bbf1126c3
commit 02e01fb2d6
217 changed files with 26395 additions and 21194 deletions
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libs/sqlalchemy/dialects/sqlite/__init__.py
+3 -3
View File
@@ -1,5 +1,5 @@
# sqlite/__init__.py
# Copyright (C) 2005-2011 the SQLAlchemy authors and contributors <see AUTHORS file>
# Copyright (C) 2005-2012 the SQLAlchemy authors and contributors <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
@@ -11,10 +11,10 @@ base.dialect = pysqlite.dialect
from sqlalchemy.dialects.sqlite.base import \
BLOB, BOOLEAN, CHAR, DATE, DATETIME, DECIMAL, FLOAT, INTEGER,\
BLOB, BOOLEAN, CHAR, DATE, DATETIME, DECIMAL, FLOAT, INTEGER, REAL,\
NUMERIC, SMALLINT, TEXT, TIME, TIMESTAMP, VARCHAR, dialect
__all__ = (
'BLOB', 'BOOLEAN', 'CHAR', 'DATE', 'DATETIME', 'DECIMAL', 'FLOAT', 'INTEGER',
'NUMERIC', 'SMALLINT', 'TEXT', 'TIME', 'TIMESTAMP', 'VARCHAR', 'dialect'
'NUMERIC', 'SMALLINT', 'TEXT', 'TIME', 'TIMESTAMP', 'VARCHAR', 'dialect', 'REAL'
)
libs/sqlalchemy/dialects/sqlite/base.py
+203 -52
View File
@@ -1,5 +1,5 @@
# sqlite/base.py
# Copyright (C) 2005-2011 the SQLAlchemy authors and contributors <see AUTHORS file>
# Copyright (C) 2005-2012 the SQLAlchemy authors and contributors <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
@@ -16,7 +16,7 @@ SQLite does not have built-in DATE, TIME, or DATETIME types, and pysqlite does n
out of the box functionality for translating values between Python `datetime` objects
and a SQLite-supported format. SQLAlchemy's own :class:`~sqlalchemy.types.DateTime`
and related types provide date formatting and parsing functionality when SQlite is used.
The implementation classes are :class:`DATETIME`, :class:`DATE` and :class:`TIME`.
The implementation classes are :class:`~.sqlite.DATETIME`, :class:`~.sqlite.DATE` and :class:`~.sqlite.TIME`.
These types represent dates and times as ISO formatted strings, which also nicely
support ordering. There's no reliance on typical "libc" internals for these functions
so historical dates are fully supported.
@@ -46,41 +46,74 @@ to the Table construct::
Transaction Isolation Level
---------------------------
:func:`create_engine` accepts an ``isolation_level`` parameter which results in
:func:`.create_engine` accepts an ``isolation_level`` parameter which results in
the command ``PRAGMA read_uncommitted <level>`` being invoked for every new
connection. Valid values for this parameter are ``SERIALIZABLE`` and
``READ UNCOMMITTED`` corresponding to a value of 0 and 1, respectively.
See the section :ref:`pysqlite_serializable` for an important workaround
when using serializable isolation with Pysqlite.
"""
import datetime, re, time
import datetime, re
from sqlalchemy import schema as sa_schema
from sqlalchemy import sql, exc, pool, DefaultClause
from sqlalchemy.engine import default
from sqlalchemy.engine import reflection
from sqlalchemy import sql, exc
from sqlalchemy.engine import default, base, reflection
from sqlalchemy import types as sqltypes
from sqlalchemy import util
from sqlalchemy.sql import compiler, functions as sql_functions
from sqlalchemy.util import NoneType
from sqlalchemy.sql import compiler
from sqlalchemy import processors
from sqlalchemy.types import BLOB, BOOLEAN, CHAR, DATE, DATETIME, DECIMAL,\
FLOAT, INTEGER, NUMERIC, SMALLINT, TEXT, TIME,\
TIMESTAMP, VARCHAR
FLOAT, REAL, INTEGER, NUMERIC, SMALLINT, TEXT, TIME, TIMESTAMP, VARCHAR
class _DateTimeMixin(object):
_reg = None
_storage_format = None
def __init__(self, storage_format=None, regexp=None, **kwargs):
def __init__(self, storage_format=None, regexp=None, **kw):
super(_DateTimeMixin, self).__init__(**kw)
if regexp is not None:
self._reg = re.compile(regexp)
if storage_format is not None:
self._storage_format = storage_format
class DATETIME(_DateTimeMixin, sqltypes.DateTime):
"""Represent a Python datetime object in SQLite using a string.
The default string storage format is::
"%04d-%02d-%02d %02d:%02d:%02d.%06d" % (value.year,
value.month, value.day,
value.hour, value.minute,
value.second, value.microsecond)
e.g.::
2011-03-15 12:05:57.10558
The storage format can be customized to some degree using the
``storage_format`` and ``regexp`` parameters, such as::
import re
from sqlalchemy.dialects.sqlite import DATETIME
dt = DATETIME(
storage_format="%04d/%02d/%02d %02d-%02d-%02d-%06d",
regexp=re.compile("(\d+)/(\d+)/(\d+) (\d+)-(\d+)-(\d+)(?:-(\d+))?")
)
:param storage_format: format string which will be appled to the
tuple ``(value.year, value.month, value.day, value.hour,
value.minute, value.second, value.microsecond)``, given a
Python datetime.datetime() object.
:param regexp: regular expression which will be applied to
incoming result rows. The resulting match object is appled to
the Python datetime() constructor via ``*map(int,
match_obj.groups(0))``.
"""
_storage_format = "%04d-%02d-%02d %02d:%02d:%02d.%06d"
def bind_processor(self, dialect):
@@ -110,6 +143,38 @@ class DATETIME(_DateTimeMixin, sqltypes.DateTime):
return processors.str_to_datetime
class DATE(_DateTimeMixin, sqltypes.Date):
"""Represent a Python date object in SQLite using a string.
The default string storage format is::
"%04d-%02d-%02d" % (value.year, value.month, value.day)
e.g.::
2011-03-15
The storage format can be customized to some degree using the
``storage_format`` and ``regexp`` parameters, such as::
import re
from sqlalchemy.dialects.sqlite import DATE
d = DATE(
storage_format="%02d/%02d/%02d",
regexp=re.compile("(\d+)/(\d+)/(\d+)")
)
:param storage_format: format string which will be appled to the
tuple ``(value.year, value.month, value.day)``,
given a Python datetime.date() object.
:param regexp: regular expression which will be applied to
incoming result rows. The resulting match object is appled to
the Python date() constructor via ``*map(int,
match_obj.groups(0))``.
"""
_storage_format = "%04d-%02d-%02d"
def bind_processor(self, dialect):
@@ -133,6 +198,40 @@ class DATE(_DateTimeMixin, sqltypes.Date):
return processors.str_to_date
class TIME(_DateTimeMixin, sqltypes.Time):
"""Represent a Python time object in SQLite using a string.
The default string storage format is::
"%02d:%02d:%02d.%06d" % (value.hour, value.minute,
value.second,
value.microsecond)
e.g.::
12:05:57.10558
The storage format can be customized to some degree using the
``storage_format`` and ``regexp`` parameters, such as::
import re
from sqlalchemy.dialects.sqlite import TIME
t = TIME(
storage_format="%02d-%02d-%02d-%06d",
regexp=re.compile("(\d+)-(\d+)-(\d+)-(?:-(\d+))?")
)
:param storage_format: format string which will be appled
to the tuple ``(value.hour, value.minute, value.second,
value.microsecond)``, given a Python datetime.time() object.
:param regexp: regular expression which will be applied to
incoming result rows. The resulting match object is appled to
the Python time() constructor via ``*map(int,
match_obj.groups(0))``.
"""
_storage_format = "%02d:%02d:%02d.%06d"
def bind_processor(self, dialect):
@@ -174,7 +273,7 @@ ischema_names = {
'INT': sqltypes.INTEGER,
'INTEGER': sqltypes.INTEGER,
'NUMERIC': sqltypes.NUMERIC,
'REAL': sqltypes.Numeric,
'REAL': sqltypes.REAL,
'SMALLINT': sqltypes.SMALLINT,
'TEXT': sqltypes.TEXT,
'TIME': sqltypes.TIME,
@@ -203,6 +302,12 @@ class SQLiteCompiler(compiler.SQLCompiler):
def visit_now_func(self, fn, **kw):
return "CURRENT_TIMESTAMP"
def visit_true(self, expr, **kw):
return '1'
def visit_false(self, expr, **kw):
return '0'
def visit_char_length_func(self, fn, **kw):
return "length%s" % self.function_argspec(fn)
@@ -217,19 +322,19 @@ class SQLiteCompiler(compiler.SQLCompiler):
return "CAST(STRFTIME('%s', %s) AS INTEGER)" % (
self.extract_map[extract.field], self.process(extract.expr, **kw))
except KeyError:
raise exc.ArgumentError(
raise exc.CompileError(
"%s is not a valid extract argument." % extract.field)
def limit_clause(self, select):
text = ""
if select._limit is not None:
text += " \n LIMIT " + str(select._limit)
text += "\n LIMIT " + self.process(sql.literal(select._limit))
if select._offset is not None:
if select._limit is None:
text += " \n LIMIT -1"
text += " OFFSET " + str(select._offset)
text += "\n LIMIT " + self.process(sql.literal(-1))
text += " OFFSET " + self.process(sql.literal(select._offset))
else:
text += " OFFSET 0"
text += " OFFSET " + self.process(sql.literal(0))
return text
def for_update_clause(self, select):
@@ -251,7 +356,7 @@ class SQLiteDDLCompiler(compiler.DDLCompiler):
if column.primary_key and \
column.table.kwargs.get('sqlite_autoincrement', False) and \
len(column.table.primary_key.columns) == 1 and \
isinstance(column.type, sqltypes.Integer) and \
issubclass(column.type._type_affinity, sqltypes.Integer) and \
not column.foreign_keys:
colspec += " PRIMARY KEY AUTOINCREMENT"
@@ -265,7 +370,7 @@ class SQLiteDDLCompiler(compiler.DDLCompiler):
c = list(constraint)[0]
if c.primary_key and \
c.table.kwargs.get('sqlite_autoincrement', False) and \
isinstance(c.type, sqltypes.Integer) and \
issubclass(c.type._type_affinity, sqltypes.Integer) and \
not c.foreign_keys:
return None
@@ -336,6 +441,20 @@ class SQLiteIdentifierPreparer(compiler.IdentifierPreparer):
result = self.quote_schema(index.table.schema, index.table.quote_schema) + "." + result
return result
class SQLiteExecutionContext(default.DefaultExecutionContext):
def get_result_proxy(self):
rp = base.ResultProxy(self)
if rp._metadata:
# adjust for dotted column names. SQLite
# in the case of UNION may store col names as
# "tablename.colname"
# in cursor.description
for colname in rp._metadata.keys:
if "." in colname:
trunc_col = colname.split(".")[1]
rp._metadata._set_keymap_synonym(trunc_col, colname)
return rp
class SQLiteDialect(default.DefaultDialect):
name = 'sqlite'
supports_alter = False
@@ -353,17 +472,13 @@ class SQLiteDialect(default.DefaultDialect):
ischema_names = ischema_names
colspecs = colspecs
isolation_level = None
execution_ctx_cls = SQLiteExecutionContext
supports_cast = True
supports_default_values = True
def __init__(self, isolation_level=None, native_datetime=False, **kwargs):
default.DefaultDialect.__init__(self, **kwargs)
if isolation_level and isolation_level not in ('SERIALIZABLE',
'READ UNCOMMITTED'):
raise exc.ArgumentError("Invalid value for isolation_level. "
"Valid isolation levels for sqlite are 'SERIALIZABLE' and "
"'READ UNCOMMITTED'.")
self.isolation_level = isolation_level
# this flag used by pysqlite dialect, and perhaps others in the
@@ -378,18 +493,49 @@ class SQLiteDialect(default.DefaultDialect):
self.supports_cast = \
self.dbapi.sqlite_version_info >= (3, 2, 3)
_isolation_lookup = {
'READ UNCOMMITTED':1,
'SERIALIZABLE':0
}
def set_isolation_level(self, connection, level):
try:
isolation_level = self._isolation_lookup[level.replace('_', ' ')]
except KeyError:
raise exc.ArgumentError(
"Invalid value '%s' for isolation_level. "
"Valid isolation levels for %s are %s" %
(level, self.name, ", ".join(self._isolation_lookup))
)
cursor = connection.cursor()
cursor.execute("PRAGMA read_uncommitted = %d" % isolation_level)
cursor.close()
def get_isolation_level(self, connection):
cursor = connection.cursor()
cursor.execute('PRAGMA read_uncommitted')
res = cursor.fetchone()
if res:
value = res[0]
else:
# http://www.sqlite.org/changes.html#version_3_3_3
# "Optional READ UNCOMMITTED isolation (instead of the
# default isolation level of SERIALIZABLE) and
# table level locking when database connections
# share a common cache.""
# pre-SQLite 3.3.0 default to 0
value = 0
cursor.close()
if value == 0:
return "SERIALIZABLE"
elif value == 1:
return "READ UNCOMMITTED"
else:
assert False, "Unknown isolation level %s" % value
def on_connect(self):
if self.isolation_level is not None:
if self.isolation_level == 'READ UNCOMMITTED':
isolation_level = 1
else:
isolation_level = 0
def connect(conn):
cursor = conn.cursor()
cursor.execute("PRAGMA read_uncommitted = %d" % isolation_level)
cursor.close()
self.set_isolation_level(conn, self.isolation_level)
return connect
else:
return None
@@ -410,7 +556,6 @@ class SQLiteDialect(default.DefaultDialect):
"WHERE type='table' ORDER BY name")
rs = connection.execute(s)
except exc.DBAPIError:
raise
s = ("SELECT name FROM sqlite_master "
"WHERE type='table' ORDER BY name")
rs = connection.execute(s)
@@ -429,7 +574,7 @@ class SQLiteDialect(default.DefaultDialect):
# consume remaining rows, to work around
# http://www.sqlite.org/cvstrac/tktview?tn=1884
while cursor.fetchone() is not None:
while not cursor.closed and cursor.fetchone() is not None:
pass
return (row is not None)
@@ -450,7 +595,6 @@ class SQLiteDialect(default.DefaultDialect):
"WHERE type='view' ORDER BY name")
rs = connection.execute(s)
except exc.DBAPIError:
raise
s = ("SELECT name FROM sqlite_master "
"WHERE type='view' ORDER BY name")
rs = connection.execute(s)
@@ -475,7 +619,6 @@ class SQLiteDialect(default.DefaultDialect):
"AND type='view'") % view_name
rs = connection.execute(s)
except exc.DBAPIError:
raise
s = ("SELECT sql FROM sqlite_master WHERE name = '%s' "
"AND type='view'") % view_name
rs = connection.execute(s)
@@ -492,17 +635,19 @@ class SQLiteDialect(default.DefaultDialect):
else:
pragma = "PRAGMA "
qtable = quote(table_name)
c = _pragma_cursor(connection.execute("%stable_info(%s)" % (pragma, qtable)))
c = _pragma_cursor(
connection.execute("%stable_info(%s)" %
(pragma, qtable)))
found_table = False
columns = []
while True:
row = c.fetchone()
if row is None:
break
(name, type_, nullable, default, has_default, primary_key) = (row[1], row[2].upper(), not row[3], row[4], row[4] is not None, row[5])
(name, type_, nullable, default, has_default, primary_key) = \
(row[1], row[2].upper(), not row[3],
row[4], row[4] is not None, row[5])
name = re.sub(r'^\"|\"$', '', name)
if default:
default = re.sub(r"^\'|\'$", '', default)
match = re.match(r'(\w+)(\(.*?\))?', type_)
if match:
coltype = match.group(1)
@@ -512,19 +657,20 @@ class SQLiteDialect(default.DefaultDialect):
args = ''
try:
coltype = self.ischema_names[coltype]
if args is not None:
args = re.findall(r'(\d+)', args)
coltype = coltype(*[int(a) for a in args])
except KeyError:
util.warn("Did not recognize type '%s' of column '%s'" %
(coltype, name))
coltype = sqltypes.NullType
if args is not None:
args = re.findall(r'(\d+)', args)
coltype = coltype(*[int(a) for a in args])
coltype = sqltypes.NullType()
columns.append({
'name' : name,
'type' : coltype,
'nullable' : nullable,
'default' : default,
'autoincrement':default is None,
'primary_key': primary_key
})
return columns
@@ -553,22 +699,26 @@ class SQLiteDialect(default.DefaultDialect):
row = c.fetchone()
if row is None:
break
(constraint_name, rtbl, lcol, rcol) = (row[0], row[2], row[3], row[4])
(numerical_id, rtbl, lcol, rcol) = (row[0], row[2], row[3], row[4])
# sqlite won't return rcol if the table
# was created with REFERENCES <tablename>, no col
if rcol is None:
rcol = lcol
rtbl = re.sub(r'^\"|\"$', '', rtbl)
lcol = re.sub(r'^\"|\"$', '', lcol)
rcol = re.sub(r'^\"|\"$', '', rcol)
try:
fk = fks[constraint_name]
fk = fks[numerical_id]
except KeyError:
fk = {
'name' : constraint_name,
'name' : None,
'constrained_columns' : [],
'referred_schema' : None,
'referred_table' : rtbl,
'referred_columns' : []
}
fkeys.append(fk)
fks[constraint_name] = fk
fks[numerical_id] = fk
# look up the table based on the given table's engine, not 'self',
# since it could be a ProxyEngine
@@ -612,7 +762,8 @@ class SQLiteDialect(default.DefaultDialect):
def _pragma_cursor(cursor):
"""work around SQLite issue whereby cursor.description is blank when PRAGMA returns no rows."""
"""work around SQLite issue whereby cursor.description
is blank when PRAGMA returns no rows."""
if cursor.closed:
cursor.fetchone = lambda: None
libs/sqlalchemy/dialects/sqlite/pysqlite.py
+121 -43
View File
@@ -1,5 +1,5 @@
# sqlite/pysqlite.py
# Copyright (C) 2005-2011 the SQLAlchemy authors and contributors <see AUTHORS file>
# Copyright (C) 2005-2012 the SQLAlchemy authors and contributors <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
@@ -93,61 +93,130 @@ processing. Execution of "func.current_date()" will return a string.
"func.current_timestamp()" is registered as returning a DATETIME type in
SQLAlchemy, so this function still receives SQLAlchemy-level result processing.
Threading Behavior
------------------
Threading/Pooling Behavior
---------------------------
Pysqlite connections do not support being moved between threads, unless
the ``check_same_thread`` Pysqlite flag is set to ``False``. In addition,
when using an in-memory SQLite database, the full database exists only within
the scope of a single connection. It is reported that an in-memory
database does not support being shared between threads regardless of the
``check_same_thread`` flag - which means that a multithreaded
application **cannot** share data from a ``:memory:`` database across threads
unless access to the connection is limited to a single worker thread which communicates
through a queueing mechanism to concurrent threads.
Pysqlite's default behavior is to prohibit the usage of a single connection
in more than one thread. This is controlled by the ``check_same_thread``
Pysqlite flag. This default is intended to work with older versions
of SQLite that did not support multithreaded operation under
various circumstances. In particular, older SQLite versions
did not allow a ``:memory:`` database to be used in multiple threads
under any circumstances.
To provide a default which accomodates SQLite's default threading capabilities
somewhat reasonably, the SQLite dialect will specify that the :class:`~sqlalchemy.pool.SingletonThreadPool`
be used by default. This pool maintains a single SQLite connection per thread
that is held open up to a count of five concurrent threads. When more than five threads
are used, a cleanup mechanism will dispose of excess unused connections.
SQLAlchemy sets up pooling to work with Pysqlite's default behavior:
Two optional pool implementations that may be appropriate for particular SQLite usage scenarios:
* When a ``:memory:`` SQLite database is specified, the dialect by default will use
:class:`.SingletonThreadPool`. This pool maintains a single connection per
thread, so that all access to the engine within the current thread use the
same ``:memory:`` database - other threads would access a different
``:memory:`` database.
* When a file-based database is specified, the dialect will use :class:`.NullPool`
as the source of connections. This pool closes and discards connections
which are returned to the pool immediately. SQLite file-based connections
have extremely low overhead, so pooling is not necessary. The scheme also
prevents a connection from being used again in a different thread and works
best with SQLite's coarse-grained file locking.
* the :class:`sqlalchemy.pool.StaticPool` might be appropriate for a multithreaded
application using an in-memory database, assuming the threading issues inherent in
pysqlite are somehow accomodated for. This pool holds persistently onto a single connection
which is never closed, and is returned for all requests.
.. note::
The default selection of :class:`.NullPool` for SQLite file-based databases
is new in SQLAlchemy 0.7. Previous versions
select :class:`.SingletonThreadPool` by
default for all SQLite databases.
* the :class:`sqlalchemy.pool.NullPool` might be appropriate for an application that
makes use of a file-based sqlite database. This pool disables any actual "pooling"
behavior, and simply opens and closes real connections corresonding to the :func:`connect()`
and :func:`close()` methods. SQLite can "connect" to a particular file with very high
efficiency, so this option may actually perform better without the extra overhead
of :class:`SingletonThreadPool`. NullPool will of course render a ``:memory:`` connection
useless since the database would be lost as soon as the connection is "returned" to the pool.
Modern versions of SQLite no longer have the threading restrictions, and assuming
the sqlite3/pysqlite library was built with SQLite's default threading mode
of "Serialized", even ``:memory:`` databases can be shared among threads.
Using a Memory Database in Multiple Threads
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
To use a ``:memory:`` database in a multithreaded scenario, the same connection
object must be shared among threads, since the database exists
only within the scope of that connection. The :class:`.StaticPool` implementation
will maintain a single connection globally, and the ``check_same_thread`` flag
can be passed to Pysqlite as ``False``::
from sqlalchemy.pool import StaticPool
engine = create_engine('sqlite://',
connect_args={'check_same_thread':False},
poolclass=StaticPool)
Note that using a ``:memory:`` database in multiple threads requires a recent
version of SQLite.
Using Temporary Tables with SQLite
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Due to the way SQLite deals with temporary tables, if you wish to use a temporary table
in a file-based SQLite database across multiple checkouts from the connection pool, such
as when using an ORM :class:`.Session` where the temporary table should continue to remain
after :meth:`.commit` or :meth:`.rollback` is called,
a pool which maintains a single connection must be used. Use :class:`.SingletonThreadPool`
if the scope is only needed within the current thread, or :class:`.StaticPool` is scope is
needed within multiple threads for this case::
# maintain the same connection per thread
from sqlalchemy.pool import SingletonThreadPool
engine = create_engine('sqlite:///mydb.db',
poolclass=SingletonThreadPool)
# maintain the same connection across all threads
from sqlalchemy.pool import StaticPool
engine = create_engine('sqlite:///mydb.db',
poolclass=StaticPool)
Note that :class:`.SingletonThreadPool` should be configured for the number of threads
that are to be used; beyond that number, connections will be closed out in a non deterministic
way.
Unicode
-------
In contrast to SQLAlchemy's active handling of date and time types for pysqlite, pysqlite's
default behavior regarding Unicode is that all strings are returned as Python unicode objects
in all cases. So even if the :class:`~sqlalchemy.types.Unicode` type is
*not* used, you will still always receive unicode data back from a result set. It is
**strongly** recommended that you do use the :class:`~sqlalchemy.types.Unicode` type
to represent strings, since it will raise a warning if a non-unicode Python string is
passed from the user application. Mixing the usage of non-unicode objects with returned unicode objects can
quickly create confusion, particularly when using the ORM as internal data is not
always represented by an actual database result string.
The pysqlite driver only returns Python ``unicode`` objects in result sets, never
plain strings, and accommodates ``unicode`` objects within bound parameter
values in all cases. Regardless of the SQLAlchemy string type in use,
string-based result values will by Python ``unicode`` in Python 2.
The :class:`.Unicode` type should still be used to indicate those columns that
require unicode, however, so that non-``unicode`` values passed inadvertently
will emit a warning. Pysqlite will emit an error if a non-``unicode`` string
is passed containing non-ASCII characters.
.. _pysqlite_serializable:
Serializable Transaction Isolation
----------------------------------
The pysqlite DBAPI driver has a long-standing bug in which transactional
state is not begun until the first DML statement, that is INSERT, UPDATE
or DELETE, is emitted. A SELECT statement will not cause transactional
state to begin. While this mode of usage is fine for typical situations
and has the advantage that the SQLite database file is not prematurely
locked, it breaks serializable transaction isolation, which requires
that the database file be locked upon any SQL being emitted.
To work around this issue, the ``BEGIN`` keyword can be emitted
at the start of each transaction. The following recipe establishes
a :meth:`.ConnectionEvents.begin` handler to achieve this::
from sqlalchemy import create_engine, event
engine = create_engine("sqlite:///myfile.db", isolation_level='SERIALIZABLE')
@event.listens_for(engine, "begin")
def do_begin(conn):
conn.execute("BEGIN")
"""
from sqlalchemy.dialects.sqlite.base import SQLiteDialect, DATETIME, DATE
from sqlalchemy import schema, exc, pool
from sqlalchemy.engine import default
from sqlalchemy import exc, pool
from sqlalchemy import types as sqltypes
from sqlalchemy import util
import os
class _SQLite_pysqliteTimeStamp(DATETIME):
def bind_processor(self, dialect):
@@ -177,7 +246,6 @@ class _SQLite_pysqliteDate(DATE):
class SQLiteDialect_pysqlite(SQLiteDialect):
default_paramstyle = 'qmark'
poolclass = pool.SingletonThreadPool
colspecs = util.update_copy(
SQLiteDialect.colspecs,
@@ -215,6 +283,13 @@ class SQLiteDialect_pysqlite(SQLiteDialect):
raise e
return sqlite
@classmethod
def get_pool_class(cls, url):
if url.database and url.database != ':memory:':
return pool.NullPool
else:
return pool.SingletonThreadPool
def _get_server_version_info(self, connection):
return self.dbapi.sqlite_version_info
@@ -227,6 +302,8 @@ class SQLiteDialect_pysqlite(SQLiteDialect):
" sqlite:///relative/path/to/file.db\n"
" sqlite:////absolute/path/to/file.db" % (url,))
filename = url.database or ':memory:'
if filename != ':memory:':
filename = os.path.abspath(filename)
opts = url.query.copy()
util.coerce_kw_type(opts, 'timeout', float)
@@ -237,7 +314,8 @@ class SQLiteDialect_pysqlite(SQLiteDialect):
return ([filename], opts)
def is_disconnect(self, e):
return isinstance(e, self.dbapi.ProgrammingError) and "Cannot operate on a closed database." in str(e)
def is_disconnect(self, e, connection, cursor):
return isinstance(e, self.dbapi.ProgrammingError) and \
"Cannot operate on a closed database." in str(e)
dialect = SQLiteDialect_pysqlite