sqlalchemy-pervasive/sqlalchemy_pervasive/base.py

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#!/usr/bin/env python
# -*- coding: utf-8 -*-
################################################################################
#
# sqlalchemy-pervasive -- SQLAlchemy Dialect for Pervasive PSQL
# Copyright © 2013 Sacramento Natural Foods Co-op, Inc
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#
# This file is part of sqlalchemy-pervasive.
#
# sqlalchemy-pervasive is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by the
# Free Software Foundation, either version 3 of the License, or (at your
# option) any later version.
#
# sqlalchemy-pervasive is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
# more details.
#
# You should have received a copy of the GNU General Public License along with
# sqlalchemy-pervasive. If not, see <http://www.gnu.org/licenses/>.
#
################################################################################
"""
Support for the Pervasive PSQL database engine.
"""
from sqlalchemy.sql.compiler import SQLCompiler
from sqlalchemy.engine.default import DefaultDialect
from sqlalchemy.exc import InvalidRequestError
class PervasiveCompiler(SQLCompiler):
"""
Custom SQL statement compiler for Pervasive PSQL.
"""
def get_select_precolumns(self, select):
# This logic was copied from the ``sqlalchemy-access`` dialect.
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s = 'DISTINCT ' if select._distinct else ''
if select._limit:
s += 'TOP {0} '.format(select._limit)
if select._offset:
raise InvalidRequestError(
"Pervasive PSQL does not support limit with an offset")
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return s
def limit_clause(self, select):
return ''
def visit_true(self, expr, **kw):
return '1'
def visit_false(self, expr, **kw):
return '0'
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class PervasiveDialect(DefaultDialect):
name = 'pervasive'
statement_compiler = PervasiveCompiler