62 lines
2 KiB
Python
62 lines
2 KiB
Python
# -*- coding: utf-8; -*-
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################################################################################
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#
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# sqlalchemy-pervasive -- SQLAlchemy Dialect for Pervasive PSQL
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# Copyright © 2013-2021 Sacramento Natural Foods Co-op, Inc
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#
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# This file is part of sqlalchemy-pervasive.
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#
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# sqlalchemy-pervasive is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by the
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# Free Software Foundation, either version 3 of the License, or (at your
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# option) any later version.
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#
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# sqlalchemy-pervasive is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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# more details.
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#
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# You should have received a copy of the GNU General Public License along with
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# sqlalchemy-pervasive. If not, see <http://www.gnu.org/licenses/>.
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#
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################################################################################
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"""
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Support for the Pervasive PSQL database engine.
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"""
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from sqlalchemy.sql.compiler import SQLCompiler
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from sqlalchemy.engine.default import DefaultDialect
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from sqlalchemy.exc import InvalidRequestError
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class PervasiveCompiler(SQLCompiler):
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"""
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Custom SQL statement compiler for Pervasive PSQL.
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"""
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def get_select_precolumns(self, select):
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# This logic was copied from the ``sqlalchemy-access`` dialect.
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s = 'DISTINCT ' if select._distinct else ''
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if select._limit:
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s += 'TOP {0} '.format(select._limit)
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if select._offset:
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raise InvalidRequestError(
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"Pervasive PSQL does not support limit with an offset")
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return s
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def limit_clause(self, select):
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return ''
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def visit_true(self, expr, **kw):
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return '1'
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def visit_false(self, expr, **kw):
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return '0'
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class PervasiveDialect(DefaultDialect):
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name = 'pervasive'
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statement_compiler = PervasiveCompiler
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