# engine/default.py
# Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Michael Bayer mike_mp@zzzcomputing.com
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""Default implementations of per-dialect sqlalchemy.engine classes.
These are semi-private implementation classes which are only of importance
to database dialect authors; dialects will usually use the classes here
as the base class for their own corresponding classes.
"""
import re, random
from sqlalchemy.engine import base,reflection
from sqlalchemy.sql import compiler,expression
from sqlalchemy import exc,types
AUTOCOMMIT_REGEXP = re.compile(r'\s*(?:UPDATE|INSERT|CREATE|DELETE|DROP|ALTER)',
re.I | re.UNICODE)
class DefaultDialect(base.Dialect):
"""Default implementation of Dialect"""
statement_compiler = compiler.SQLCompiler
ddl_compiler = compiler.DDLCompiler
type_compiler = compiler.GenericTypeCompiler
preparer = compiler.IdentifierPreparer
supports_alter = True
# most DBAPIs happy with this for execute().
# not cx_oracle.
execute_sequence_format = tuple
supports_sequences = False
sequences_optional = False
preexecute_autoincrement_sequences = False
postfetch_lastrowid = True
implicit_returning = False
supports_native_enum = False
supports_native_boolean = False
# if the NUMERIC type
# returns decimal.Decimal.
# *not* the FLOAT type however.
supports_native_decimal = False
# Py3K
#supports_unicode_statements = True
#supports_unicode_binds = True
# Py2K
supports_unicode_statements = False
supports_unicode_binds = False
returns_unicode_strings = False
# end Py2K
name = 'default'
max_identifier_length = 9999
supports_sane_rowcount = True
supports_sane_multi_rowcount = True
dbapi_type_map = {}
colspecs = {}
default_paramstyle = 'named'
supports_default_values = False
supports_empty_insert = True
server_version_info = None
# indicates symbol names are
# UPPERCASEd if they are case insensitive
# within the database.
# if this is True, the methods normalize_name()
# and denormalize_name() must be provided.
requires_name_normalize = False
reflection_options = ()
def __init__(self, convert_unicode=False, assert_unicode=False,
encoding='utf-8', paramstyle=None, dbapi=None,
implicit_returning=None,
label_length=None, **kwargs):
if not getattr(self, 'ported_sqla_06', True):
util.warn(
"The %s dialect is not yet ported to SQLAlchemy 0.6" % self.name)
self.convert_unicode = convert_unicode
if assert_unicode:
util.warn_deprecated("assert_unicode is deprecated. "
"SQLAlchemy emits a warning in all cases where it "
"would otherwise like to encode a Python unicode object "
"into a specific encoding but a plain bytestring is received. "
"This does *not* apply to DBAPIs that coerce Unicode natively."
)
self.encoding = encoding
self.positional = False
self._ischema = None
self.dbapi = dbapi
if paramstyle is not None:
self.paramstyle = paramstyle
elif self.dbapi is not None:
self.paramstyle = self.dbapi.paramstyle
else:
self.paramstyle = self.default_paramstyle
if implicit_returning is not None:
self.implicit_returning = implicit_returning
self.positional = self.paramstyle in ('qmark', 'format', 'numeric')
self.identifier_preparer = self.preparer(self)
self.type_compiler = self.type_compiler(self)
if label_length and label_length > self.max_identifier_length:
raise exc.ArgumentError("Label length of %d is greater than this dialect's"
" maximum identifier length of %d" %
(label_length, self.max_identifier_length))
self.label_length = label_length
if not hasattr(self, 'description_encoding'):
self.description_encoding = getattr(self, 'description_encoding', encoding)
@property
def dialect_description(self):
return self.name + "+" + self.driver
def initialize(self, connection):
try:
self.server_version_info = self._get_server_version_info(connection)
except NotImplementedError:
self.server_version_info = None
try:
self.default_schema_name = self._get_default_schema_name(connection)
except NotImplementedError:
self.default_schema_name = None
self.returns_unicode_strings = self._check_unicode_returns(connection)
self.do_rollback(connection.connection)
def on_connect(self):
"""return a callable which sets up a newly created DBAPI connection.
This is used to set dialect-wide per-connection options such as isolation
modes, unicode modes, etc.
If a callable is returned, it will be assembled into a pool listener
that receives the direct DBAPI connection, with all wrappers removed.
If None is returned, no listener will be generated.
"""
return None
def _check_unicode_returns(self, connection):
# Py2K
if self.supports_unicode_statements:
cast_to = unicode
else:
cast_to = str
# end Py2K
# Py3K
#cast_to = str
def check_unicode(type_):
cursor = connection.connection.cursor()
try:
cursor.execute(
cast_to(
expression.select(
[expression.cast(
expression.literal_column("'test unicode returns'"), type_)
]).compile(dialect=self)
)
)
row = cursor.fetchone()
return isinstance(row[0], unicode)
finally:
cursor.close()
# detect plain VARCHAR
unicode_for_varchar = check_unicode(sqltypes.VARCHAR(60))
# detect if there's an NVARCHAR type with different behavior available
unicode_for_unicode = check_unicode(sqltypes.Unicode(60))
if unicode_for_unicode and not unicode_for_varchar:
return "conditional"
else:
return unicode_for_varchar
def type_descriptor(self, typeobj):
"""Provide a database-specific ``TypeEngine`` object, given
the generic object which comes from the types module.
This method looks for a dictionary called
``colspecs`` as a class or instance-level variable,
and passes on to ``types.adapt_type()``.
"""
return sqltypes.adapt_type(typeobj, self.colspecs)
def reflecttable(self, connection, table, include_columns):
insp = reflection.Inspector.from_engine(connection)
return insp.reflecttable(table, include_columns)
def get_pk_constraint(self, conn, table_name, schema=None, **kw):
"""Compatiblity method, adapts the result of get_primary_keys()
for those dialects which don't implement get_pk_constraint().
"""
return {
'constrained_columns':
self.get_primary_keys(conn, table_name,
schema=schema, **kw)
}
def validate_identifier(self, ident):
if len(ident) > self.max_identifier_length:
raise exc.IdentifierError(
"Identifier '%s' exceeds maximum length of %d characters" %
(ident, self.max_identifier_length)
)
def connect(self, *cargs, **cparams):
return self.dbapi.connect(*cargs, **cparams)
def create_connect_args(self, url):
opts = url.translate_connect_args()
opts.update(url.query)
return [[], opts]
def do_begin(self, connection):
"""Implementations might want to put logic here for turning
autocommit on/off, etc.
"""
pass
def do_rollback(self, connection):
"""Implementations might want to put logic here for turning
autocommit on/off, etc.
"""
connection.rollback()
def do_commit(self, connection):
"""Implementations might want to put logic here for turning
autocommit on/off, etc.
"""
connection.commit()
def create_xid(self):
"""Create a random two-phase transaction ID.
This id will be passed to do_begin_twophase(), do_rollback_twophase(),
do_commit_twophase(). Its format is unspecified.
"""
return "_sa_%032x" % random.randint(0, 2 ** 128)
def do_savepoint(self, connection, name):
connection.execute(expression.SavepointClause(name))
def do_rollback_to_savepoint(self, connection, name):
connection.execute(expression.RollbackToSavepointClause(name))
def do_release_savepoint(self, connection, name):
connection.execute(expression.ReleaseSavepointClause(name))
def do_executemany(self, cursor, statement, parameters, context=None):
cursor.executemany(statement, parameters)
def do_execute(self, cursor, statement, parameters, context=None):
cursor.execute(statement, parameters)
def is_disconnect(self, e):
return False
class DefaultExecutionContext(base.ExecutionContext):
execution_options = util.frozendict()
isinsert = False
isupdate = False
isdelete = False
isddl = False
executemany = False
result_map = None
compiled = None
statement = None
def __init__(self,
dialect,
connection,
compiled_sql=None,
compiled_ddl=None,
statement=None,
parameters=None):
self.dialect = dialect
self._connection = self.root_connection = connection
self.engine = connection.engine
if compiled_ddl is not None:
self.compiled = compiled = compiled_ddl
self.isddl = True
if compiled.statement._execution_options:
self.execution_options = compiled.statement._execution_options
if connection._execution_options:
self.execution_options = self.execution_options.union(
connection._execution_options
)
if not dialect.supports_unicode_statements:
self.unicode_statement = unicode(compiled)
self.statement = self.unicode_statement.encode(self.dialect.encoding)
else:
self.statement = self.unicode_statement = unicode(compiled)
self.cursor = self.create_cursor()
self.compiled_parameters = []
self.parameters = [self._default_params]
elif compiled_sql is not None:
self.compiled = compiled = compiled_sql
if not compiled.can_execute:
raise exc.ArgumentError("Not an executable clause: %s" % compiled)
if compiled.statement._execution_options:
self.execution_options = compiled.statement._execution_options
if connection._execution_options:
self.execution_options = self.execution_options.union(
connection._execution_options
)
# compiled clauseelement. process bind params, process table defaults,
# track collections used by ResultProxy to target and process results
self.processors = dict(
(key, value) for key, value in
( (compiled.bind_names[bindparam],
bindparam.bind_processor(self.dialect))
for bindparam in compiled.bind_names )
if value is not None)
self.result_map = compiled.result_map
if not dialect.supports_unicode_statements:
self.unicode_statement = unicode(compiled)
self.statement = self.unicode_statement.encode(self.dialect.encoding)
else:
self.statement = self.unicode_statement = unicode(compiled)
self.isinsert = compiled.isinsert
self.isupdate = compiled.isupdate
self.isdelete = compiled.isdelete
if not parameters:
self.compiled_parameters = [compiled.construct_params()]
else:
self.compiled_parameters = [compiled.construct_params(m, _group_number=grp) for
grp,m in enumerate(parameters)]
self.executemany = len(parameters) > 1
self.cursor = self.create_cursor()
if self.isinsert or self.isupdate:
self.__process_defaults()
self.parameters = self.__convert_compiled_params(self.compiled_parameters)
elif statement is not None:
# plain text statement
if connection._execution_options:
self.execution_options = self.execution_options.union(connection._execution_options)
self.parameters = self.__encode_param_keys(parameters)
self.executemany = len(parameters) > 1
if isinstance(statement, unicode) and not dialect.supports_unicode_statements:
self.unicode_statement = statement
self.statement = statement.encode(self.dialect.encoding)
else:
self.statement = self.unicode_statement = statement
self.cursor = self.create_cursor()
else:
# no statement. used for standalone ColumnDefault execution.
if connection._execution_options:
self.execution_options = self.execution_options.union(connection._execution_options)
self.cursor = self.create_cursor()
@util.memoized_property
def is_crud(self):
return self.isinsert or self.isupdate or self.isdelete
@util.memoized_property
def should_autocommit(self):
autocommit = self.execution_options.get('autocommit',
not self.compiled and
self.statement and
expression.PARSE_AUTOCOMMIT
or False)
if autocommit is expression.PARSE_AUTOCOMMIT:
return self.should_autocommit_text(self.unicode_statement)
else:
return autocommit
@util.memoized_property
def _is_explicit_returning(self):
return self.compiled and \
getattr(self.compiled.statement, '_returning', False)
@util.memoized_property
def _is_implicit_returning(self):
return self.compiled and \
bool(self.compiled.returning) and \
not self.compiled.statement._returning
@util.memoized_property
def _default_params(self):
if self.dialect.positional:
return self.dialect.execute_sequence_format()
else:
return {}
def _execute_scalar(self, stmt):
"""Execute a string statement on the current cursor, returning a scalar result.
Used to fire off sequences, default phrases, and "select lastrowid"
types of statements individually
or in the context of a parent INSERT or UPDATE statement.
"""
conn = self._connection
if isinstance(stmt, unicode) and not self.dialect.supports_unicode_statements:
stmt = stmt.encode(self.dialect.encoding)
conn._cursor_execute(self.cursor, stmt, self._default_params)
return self.cursor.fetchone()[0]
@property
def connection(self):
return self._connection._branch()
def __encode_param_keys(self, params):
"""Apply string encoding to the keys of dictionary-based bind parameters.
This is only used executing textual, non-compiled SQL expressions.
"""
if not params:
return [self._default_params]
elif isinstance(params[0], self.dialect.execute_sequence_format):
return params
elif isinstance(params[0], dict):
if self.dialect.supports_unicode_statements:
return params
else:
def proc(d):
return dict((k.encode(self.dialect.encoding), d[k]) for k in d)
return [proc(d) for d in params] or [{}]
else:
return [self.dialect.execute_sequence_format(p) for p in params]
def __convert_compiled_params(self, compiled_parameters):
"""Convert the dictionary of bind parameter values into a dict or list
to be sent to the DBAPI's execute() or executemany() method.
"""
processors = self.processors
parameters = []
if self.dialect.positional:
for compiled_params in compiled_parameters:
param = []
for key in self.compiled.positiontup:
if key in processors:
param.append(processors[key](compiled_params[key]))
else:
param.append(compiled_params[key])
parameters.append(self.dialect.execute_sequence_format(param))
else:
encode = not self.dialect.supports_unicode_statements
for compiled_params in compiled_parameters:
param = {}
if encode:
encoding = self.dialect.encoding
for key in compiled_params:
if key in processors:
param[key.encode(encoding)] = processors[key](compiled_params[key])
else:
param[key.encode(encoding)] = compiled_params[key]
else:
for key in compiled_params:
if key in processors:
param[key] = processors[key](compiled_params[key])
else:
param[key] = compiled_params[key]
parameters.append(param)
return self.dialect.execute_sequence_format(parameters)
def should_autocommit_text(self, statement):
return AUTOCOMMIT_REGEXP.match(statement)
def create_cursor(self):
return self._connection.connection.cursor()
def pre_exec(self):
pass
def post_exec(self):
pass
def get_lastrowid(self):
"""return self.cursor.lastrowid, or equivalent, after an INSERT.
This may involve calling special cursor functions,
issuing a new SELECT on the cursor (or a new one),
or returning a stored value that was
calculated within post_exec().
This function will only be called for dialects
which support "implicit" primary key generation,
keep preexecute_autoincrement_sequences set to False,
and when no explicit id value was bound to the
statement.
The function is called once, directly after
post_exec() and before the transaction is committed
or ResultProxy is generated. If the post_exec()
method assigns a value to `self._lastrowid`, the
value is used in place of calling get_lastrowid().
Note that this method is *not* equivalent to the
``lastrowid`` method on ``ResultProxy``, which is a
direct proxy to the DBAPI ``lastrowid`` accessor
in all cases.
"""
return self.cursor.lastrowid
def handle_dbapi_exception(self, e):
pass
def get_result_proxy(self):
return base.ResultProxy(self)
@property
def rowcount(self):
return self.cursor.rowcount
def supports_sane_rowcount(self):
return self.dialect.supports_sane_rowcount
def supports_sane_multi_rowcount(self):
return self.dialect.supports_sane_multi_rowcount
def post_insert(self):
if self.dialect.postfetch_lastrowid and \
(not len(self._inserted_primary_key) or \
None in self._inserted_primary_key):
table = self.compiled.statement.table
lastrowid = self.get_lastrowid()
self._inserted_primary_key = [c is table._autoincrement_column and lastrowid or v
for c, v in zip(table.primary_key, self._inserted_primary_key)
]
def _fetch_implicit_returning(self, resultproxy):
table = self.compiled.statement.table
row = resultproxy.fetchone()
self._inserted_primary_key = [v is not None and v or row[c]
for c, v in zip(table.primary_key, self._inserted_primary_key)
]
def last_inserted_params(self):
return self._last_inserted_params
def last_updated_params(self):
return self._last_updated_params
def lastrow_has_defaults(self):
return hasattr(self, 'postfetch_cols') and len(self.postfetch_cols)
def set_input_sizes(self, translate=None, exclude_types=None):
"""Given a cursor and ClauseParameters, call the appropriate
style of ``setinputsizes()`` on the cursor, using DB-API types
from the bind parameter's ``TypeEngine`` objects.
"""
if not hasattr(self.compiled, 'bind_names'):
return
types = dict(
(self.compiled.bind_names[bindparam], bindparam.type)
for bindparam in self.compiled.bind_names)
if self.dialect.positional:
inputsizes = []
for key in self.compiled.positiontup:
typeengine = types[key]
dbtype = typeengine.dialect_impl(self.dialect).get_dbapi_type(self.dialect.dbapi)
if dbtype is not None and (not exclude_types or dbtype not in exclude_types):
inputsizes.append(dbtype)
try:
self.cursor.setinputsizes(*inputsizes)
except Exception, e:
self._connection._handle_dbapi_exception(e, None, None, None, self)
raise
else:
inputsizes = {}
for key in self.compiled.bind_names.values():
typeengine = types[key]
dbtype = typeengine.dialect_impl(self.dialect).get_dbapi_type(self.dialect.dbapi)
if dbtype is not None and (not exclude_types or dbtype not in exclude_types):
if translate:
key = translate.get(key, key)
inputsizes[key.encode(self.dialect.encoding)] = dbtype
try:
self.cursor.setinputsizes(**inputsizes)
except Exception, e:
self._connection._handle_dbapi_exception(e, None, None, None, self)
raise
def _exec_default(self, default):
if default.is_sequence:
return self.fire_sequence(default)
elif default.is_callable:
return default.arg(self)
elif default.is_clause_element:
# TODO: expensive branching here should be
# pulled into _exec_scalar()
conn = self.connection
c = expression.select([default.arg]).compile(bind=conn)
return conn._execute_compiled(c, (), {}).scalar()
else:
return default.arg
def get_insert_default(self, column):
if column.default is None:
return None
else:
return self._exec_default(column.default)
def get_update_default(self, column):
if column.onupdate is None:
return None
else:
return self._exec_default(column.onupdate)
def __process_defaults(self):
"""Generate default values for compiled insert/update statements,
and generate inserted_primary_key collection.
"""
if self.executemany:
if len(self.compiled.prefetch):
scalar_defaults = {}
# pre-determine scalar Python-side defaults
# to avoid many calls of get_insert_default()/get_update_default()
for c in self.compiled.prefetch:
if self.isinsert and c.default and c.default.is_scalar:
scalar_defaults[c] = c.default.arg
elif self.isupdate and c.onupdate and c.onupdate.is_scalar:
scalar_defaults[c] = c.onupdate.arg
for param in self.compiled_parameters:
self.current_parameters = param
for c in self.compiled.prefetch:
if c in scalar_defaults:
val = scalar_defaults[c]
elif self.isinsert:
val = self.get_insert_default(c)
else:
val = self.get_update_default(c)
if val is not None:
param[c.key] = val
del self.current_parameters
else:
self.current_parameters = compiled_parameters = self.compiled_parameters[0]
for c in self.compiled.prefetch:
if self.isinsert:
val = self.get_insert_default(c)
else:
val = self.get_update_default(c)
if val is not None:
compiled_parameters[c.key] = val
del self.current_parameters
if self.isinsert:
self._inserted_primary_key = [compiled_parameters.get(c.key, None)
for c in self.compiled.statement.table.primary_key]
self._last_inserted_params = compiled_parameters
else:
self._last_updated_params = compiled_parameters
self.postfetch_cols = self.compiled.postfetch
self.prefetch_cols = self.compiled.prefetch
DefaultDialect.execution_ctx_cls = DefaultExecutionContext
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