path: root/lib/sqlalchemy/engine/default.py

# engine/default.py
# Copyright (C) 2005, 2006, 2007, 2008, 2009 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
from sqlalchemy.sql import compiler, expression
from sqlalchemy import exc

AUTOCOMMIT_REGEXP = re.compile(r'\s*(?:UPDATE|INSERT|CREATE|DELETE|DROP|ALTER)',
                               re.I | re.UNICODE)

class DefaultDialect(base.Dialect):
    """Default implementation of Dialect"""

    name = 'default'
    schemagenerator = compiler.SchemaGenerator
    schemadropper = compiler.SchemaDropper
    statement_compiler = compiler.DefaultCompiler
    preparer = compiler.IdentifierPreparer
    defaultrunner = base.DefaultRunner
    supports_alter = True
    supports_unicode_statements = False
    max_identifier_length = 9999
    supports_sane_rowcount = True
    supports_sane_multi_rowcount = True
    preexecute_pk_sequences = False
    supports_pk_autoincrement = True
    dbapi_type_map = {}
    default_paramstyle = 'named'
    supports_default_values = False 
    supports_empty_insert = True

    def __init__(self, convert_unicode=False, assert_unicode=False,
                 encoding='utf-8', paramstyle=None, dbapi=None, 
                 label_length=None, **kwargs):
        self.convert_unicode = convert_unicode
        self.assert_unicode = assert_unicode
        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
        self.positional = self.paramstyle in ('qmark', 'format', 'numeric')
        self.identifier_preparer = self.preparer(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
        self.description_encoding = getattr(self, 'description_encoding', encoding)

    def type_descriptor(self, typeobj):
        """Provide a database-specific ``TypeEngine`` object, given
        the generic object which comes from the types module.

        Subclasses will usually use the ``adapt_type()`` method in the
        types module to make this job easy."""

        if type(typeobj) is type:
            typeobj = typeobj()
        return typeobj

    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 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):
    def __init__(self, dialect, connection, compiled=None, statement=None, parameters=None):
        self.dialect = dialect
        self._connection = self.root_connection = connection
        self.compiled = compiled
        self.engine = connection.engine

        if compiled is not None:
            # compiled clauseelement.  process bind params, process table defaults,
            # track collections used by ResultProxy to target and process results

            if not compiled.can_execute:
                raise exc.ArgumentError("Not an executable clause: %s" % compiled)

            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.statement = unicode(compiled).encode(self.dialect.encoding)
            else:
                self.statement = unicode(compiled)

            self.isinsert = compiled.isinsert
            self.isupdate = compiled.isupdate
            self.should_autocommit = compiled.statement._autocommit
            if isinstance(compiled.statement, expression._TextClause):
                self.should_autocommit = self.should_autocommit or self.should_autocommit_text(self.statement)

            if not parameters:
                self.compiled_parameters = [compiled.construct_params()]
                self.executemany = False
            else:
                self.compiled_parameters = [compiled.construct_params(m) for m in 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.
            self.result_map = None
            self.parameters = self.__encode_param_keys(parameters)
            self.executemany = len(parameters) > 1
            if isinstance(statement, unicode) and not dialect.supports_unicode_statements:
                self.statement = statement.encode(self.dialect.encoding)
            else:
                self.statement = statement
            self.isinsert = self.isupdate = False
            self.cursor = self.create_cursor()
            self.should_autocommit = self.should_autocommit_text(statement)
        else:
            # no statement. used for standalone ColumnDefault execution.
            self.statement = None
            self.isinsert = self.isupdate = self.executemany = self.should_autocommit = False
            self.cursor = self.create_cursor()

    @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 self.dialect.positional or self.dialect.supports_unicode_statements:
            if params:
                return params
            elif self.dialect.positional:
                return [()]
            else:
                return [{}]
        else:
            def proc(d):
                # sigh, sometimes we get positional arguments with a dialect
                # that doesnt specify positional (because of execute_text())
                if not isinstance(d, dict):
                    return d
                return dict((k.encode(self.dialect.encoding), d[k]) for k in d)
            return [proc(d) for d in params] or [{}]

    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(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 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 handle_dbapi_exception(self, e):
        pass

    def get_result_proxy(self):
        return base.ResultProxy(self)

    def get_rowcount(self):
        if hasattr(self, '_rowcount'):
            return self._rowcount
        else:
            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 last_inserted_ids(self):
        return self._last_inserted_ids

    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):
        """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.
        """

        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:
                    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:
                    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 __process_defaults(self):
        """generate default values for compiled insert/update statements,
        and generate last_inserted_ids() collection."""

        if self.executemany:
            if len(self.compiled.prefetch):
                drunner = self.dialect.defaultrunner(self)
                params = self.compiled_parameters
                for param in params:
                    # assign each dict of params to self.compiled_parameters;
                    # this allows user-defined default generators to access the full
                    # set of bind params for the row
                    self.compiled_parameters = param
                    for c in self.compiled.prefetch:
                        if self.isinsert:
                            val = drunner.get_column_default(c)
                        else:
                            val = drunner.get_column_onupdate(c)
                        if val is not None:
                            param[c.key] = val
                self.compiled_parameters = params

        else:
            compiled_parameters = self.compiled_parameters[0]
            drunner = self.dialect.defaultrunner(self)

            for c in self.compiled.prefetch:
                if self.isinsert:
                    val = drunner.get_column_default(c)
                else:
                    val = drunner.get_column_onupdate(c)

                if val is not None:
                    compiled_parameters[c.key] = val

            if self.isinsert:
                self._last_inserted_ids = [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