# engine/default.py # Copyright (C) 2005-2013 the SQLAlchemy authors and contributors # # 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 as sqltypes, util, pool, processors import codecs import weakref 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_views = True 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 #returns_unicode_strings = True #description_encoding = None # Py2K supports_unicode_statements = False supports_unicode_binds = False returns_unicode_strings = False description_encoding = 'use_encoding' # end Py2K name = 'default' # length at which to truncate # any identifier. max_identifier_length = 9999 # length at which to truncate # the name of an index. # Usually None to indicate # 'use max_identifier_length'. # thanks to MySQL, sigh max_index_name_length = None 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 0.6/0.7" % 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 self.description_encoding == 'use_encoding': self._description_decoder = processors.to_unicode_processor_factory( encoding ) elif self.description_encoding is not None: self._description_decoder = processors.to_unicode_processor_factory( self.description_encoding ) self._encoder = codecs.getencoder(self.encoding) self._decoder = processors.to_unicode_processor_factory(self.encoding) @util.memoized_property def _type_memos(self): return weakref.WeakKeyDictionary() @property def dialect_description(self): return self.name + "+" + self.driver @classmethod def get_pool_class(cls, url): return getattr(cls, 'poolclass', pool.QueuePool) 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 try: self.default_isolation_level = \ self.get_isolation_level(connection.connection) except NotImplementedError: self.default_isolation_level = 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(formatstr, type_): cursor = connection.connection.cursor() try: try: cursor.execute( cast_to( expression.select( [expression.cast( expression.literal_column( "'test %s returns'" % formatstr), type_) ]).compile(dialect=self) ) ) row = cursor.fetchone() return isinstance(row[0], unicode) except self.dbapi.Error, de: util.warn("Exception attempting to " "detect unicode returns: %r" % de) return False finally: cursor.close() # detect plain VARCHAR unicode_for_varchar = check_unicode("plain", sqltypes.VARCHAR(60)) # detect if there's an NVARCHAR type with different behavior available unicode_for_unicode = check_unicode("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, exclude_columns=None): insp = reflection.Inspector.from_engine(connection) return insp.reflecttable(table, include_columns, exclude_columns) def get_pk_constraint(self, conn, table_name, schema=None, **kw): """Compatibility 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 do_execute_no_params(self, cursor, statement, context=None): cursor.execute(statement) def is_disconnect(self, e, connection, cursor): return False def reset_isolation_level(self, dbapi_conn): # default_isolation_level is read from the first connection # after the initial set of 'isolation_level', if any, so is # the configured default of this dialect. self.set_isolation_level(dbapi_conn, self.default_isolation_level) class DefaultExecutionContext(base.ExecutionContext): isinsert = False isupdate = False isdelete = False isddl = False executemany = False result_map = None compiled = None statement = None postfetch_cols = None prefetch_cols = None _is_implicit_returning = False _is_explicit_returning = False # a hook for SQLite's translation of # result column names _translate_colname = None @classmethod def _init_ddl(cls, dialect, connection, dbapi_connection, compiled_ddl): """Initialize execution context for a DDLElement construct.""" self = cls.__new__(cls) self.dialect = dialect self.root_connection = connection self._dbapi_connection = dbapi_connection self.engine = connection.engine self.compiled = compiled = compiled_ddl self.isddl = True self.execution_options = compiled.statement._execution_options if connection._execution_options: self.execution_options = dict(self.execution_options) self.execution_options.update(connection._execution_options) if not dialect.supports_unicode_statements: self.unicode_statement = unicode(compiled) self.statement = dialect._encoder(self.unicode_statement)[0] else: self.statement = self.unicode_statement = unicode(compiled) self.cursor = self.create_cursor() self.compiled_parameters = [] if dialect.positional: self.parameters = [dialect.execute_sequence_format()] else: self.parameters = [{}] return self @classmethod def _init_compiled(cls, dialect, connection, dbapi_connection, compiled, parameters): """Initialize execution context for a Compiled construct.""" self = cls.__new__(cls) self.dialect = dialect self.root_connection = connection self._dbapi_connection = dbapi_connection self.engine = connection.engine self.compiled = compiled if not compiled.can_execute: raise exc.ArgumentError("Not an executable clause") self.execution_options = compiled.statement._execution_options if connection._execution_options: self.execution_options = dict(self.execution_options) self.execution_options.update(connection._execution_options) # compiled clauseelement. process bind params, process table defaults, # track collections used by ResultProxy to target and process results self.result_map = compiled.result_map self.unicode_statement = unicode(compiled) if not dialect.supports_unicode_statements: self.statement = self.unicode_statement.encode(self.dialect.encoding) else: self.statement = self.unicode_statement self.isinsert = compiled.isinsert self.isupdate = compiled.isupdate self.isdelete = compiled.isdelete if self.isinsert or self.isupdate or self.isdelete: self._is_explicit_returning = compiled.statement._returning self._is_implicit_returning = compiled.returning and \ not compiled.statement._returning 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.postfetch_cols = self.compiled.postfetch self.prefetch_cols = self.compiled.prefetch self.__process_defaults() processors = compiled._bind_processors # Convert the dictionary of bind parameter values # into a dict or list to be sent to the DBAPI's # execute() or executemany() method. parameters = [] if dialect.positional: for compiled_params in self.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(dialect.execute_sequence_format(param)) else: encode = not dialect.supports_unicode_statements for compiled_params in self.compiled_parameters: param = {} if encode: for key in compiled_params: if key in processors: param[dialect._encoder(key)[0]] = \ processors[key](compiled_params[key]) else: param[dialect._encoder(key)[0]] = 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) self.parameters = dialect.execute_sequence_format(parameters) return self @classmethod def _init_statement(cls, dialect, connection, dbapi_connection, statement, parameters): """Initialize execution context for a string SQL statement.""" self = cls.__new__(cls) self.dialect = dialect self.root_connection = connection self._dbapi_connection = dbapi_connection self.engine = connection.engine # plain text statement self.execution_options = connection._execution_options if not parameters: if self.dialect.positional: self.parameters = [dialect.execute_sequence_format()] else: self.parameters = [{}] elif isinstance(parameters[0], dialect.execute_sequence_format): self.parameters = parameters elif isinstance(parameters[0], dict): if dialect.supports_unicode_statements: self.parameters = parameters else: self.parameters= [ dict((dialect._encoder(k)[0], d[k]) for k in d) for d in parameters ] or [{}] else: self.parameters = [dialect.execute_sequence_format(p) for p in parameters] self.executemany = len(parameters) > 1 if not dialect.supports_unicode_statements and isinstance(statement, unicode): self.unicode_statement = statement self.statement = dialect._encoder(statement)[0] else: self.statement = self.unicode_statement = statement self.cursor = self.create_cursor() return self @classmethod def _init_default(cls, dialect, connection, dbapi_connection): """Initialize execution context for a ColumnDefault construct.""" self = cls.__new__(cls) self.dialect = dialect self.root_connection = connection self._dbapi_connection = dbapi_connection self.engine = connection.engine self.execution_options = connection._execution_options self.cursor = self.create_cursor() return self @util.memoized_property def no_parameters(self): return self.execution_options.get("no_parameters", False) @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 def _execute_scalar(self, stmt, type_): """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.root_connection if isinstance(stmt, unicode) and \ not self.dialect.supports_unicode_statements: stmt = self.dialect._encoder(stmt)[0] if self.dialect.positional: default_params = self.dialect.execute_sequence_format() else: default_params = {} conn._cursor_execute(self.cursor, stmt, default_params) r = self.cursor.fetchone()[0] if type_ is not None: # apply type post processors to the result proc = type_._cached_result_processor( self.dialect, self.cursor.description[0][1] ) if proc: return proc(r) return r @property def connection(self): return self.root_connection._branch() def should_autocommit_text(self, statement): return AUTOCOMMIT_REGEXP.match(statement) def create_cursor(self): return self._dbapi_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 not self._is_implicit_returning and \ self.dialect.postfetch_lastrowid and \ (not self.inserted_primary_key or \ None in self.inserted_primary_key): table = self.compiled.statement.table lastrowid = self.get_lastrowid() autoinc_col = table._autoincrement_column if autoinc_col is not None: # apply type post processors to the lastrowid proc = autoinc_col.type._cached_result_processor(self.dialect, None) if proc is not None: lastrowid = proc(lastrowid) self.inserted_primary_key = [ c is autoinc_col 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() ipk = [] for c, v in zip(table.primary_key, self.inserted_primary_key): if v is not None: ipk.append(v) else: ipk.append(row[c]) self.inserted_primary_key = ipk def lastrow_has_defaults(self): return (self.isinsert or self.isupdate) and \ bool(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. This method only called by those dialects which require it, currently cx_oracle. """ 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.root_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[self.dialect._encoder(key)[0]] = dbtype try: self.cursor.setinputsizes(**inputsizes) except Exception, e: self.root_connection._handle_dbapi_exception(e, None, None, None, self) raise def _exec_default(self, default, type_): if default.is_sequence: return self.fire_sequence(default, type_) 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, column.type) def get_update_default(self, column): if column.onupdate is None: return None else: return self._exec_default(column.onupdate, column.type) 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.prefetch_cols: 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.prefetch_cols: 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 = [ self.compiled_parameters[0].get(c.key, None) for c in self.compiled.\ statement.table.primary_key ] DefaultDialect.execution_ctx_cls = DefaultExecutionContext