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"""
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Module for visitor class mapping.
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"""
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import sqlalchemy as sa
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from migrate.changeset import ansisql
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from migrate.changeset.databases import (sqlite,
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postgres,
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mysql,
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oracle,
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firebird)
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# Map SA dialects to the corresponding Migrate extensions
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DIALECTS = {
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"default": ansisql.ANSIDialect,
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"sqlite": sqlite.SQLiteDialect,
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"postgres": postgres.PGDialect,
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"postgresql": postgres.PGDialect,
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"mysql": mysql.MySQLDialect,
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"oracle": oracle.OracleDialect,
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"firebird": firebird.FBDialect,
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}
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def get_engine_visitor(engine, name):
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"""
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Get the visitor implementation for the given database engine.
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:param engine: SQLAlchemy Engine
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:param name: Name of the visitor
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:type name: string
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:type engine: Engine
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:returns: visitor
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"""
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# TODO: link to supported visitors
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return get_dialect_visitor(engine.dialect, name)
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def get_dialect_visitor(sa_dialect, name):
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"""
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Get the visitor implementation for the given dialect.
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Finds the visitor implementation based on the dialect class and
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returns and instance initialized with the given name.
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Binds dialect specific preparer to visitor.
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"""
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# map sa dialect to migrate dialect and return visitor
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sa_dialect_name = getattr(sa_dialect, 'name', 'default')
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migrate_dialect_cls = DIALECTS[sa_dialect_name]
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visitor = getattr(migrate_dialect_cls, name)
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# bind preparer
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visitor.preparer = sa_dialect.preparer(sa_dialect)
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return visitor
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def run_single_visitor(engine, visitorcallable, element,
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connection=None, **kwargs):
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"""Taken from :meth:`sqlalchemy.engine.base.Engine._run_single_visitor`
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with support for migrate visitors.
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"""
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if connection is None:
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conn = engine.contextual_connect(close_with_result=False)
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else:
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conn = connection
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visitor = visitorcallable(engine.dialect, conn)
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try:
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if hasattr(element, '__migrate_visit_name__'):
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fn = getattr(visitor, 'visit_' + element.__migrate_visit_name__)
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else:
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fn = getattr(visitor, 'visit_' + element.__visit_name__)
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fn(element, **kwargs)
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finally:
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if connection is None:
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conn.close()
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