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# engine/ddl.py
# Copyright (C) 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
"""Routines to handle CREATE/DROP workflow."""
from sqlalchemy import engine, schema
from sqlalchemy.sql import util as sql_util
class DDLBase(schema.SchemaVisitor):
def __init__(self, connection):
self.connection = connection
class SchemaGenerator(DDLBase):
def __init__(self, dialect, connection, checkfirst=False, tables=None, **kwargs):
super(SchemaGenerator, self).__init__(connection, **kwargs)
self.checkfirst = checkfirst
self.tables = tables and set(tables) or None
self.preparer = dialect.identifier_preparer
self.dialect = dialect
def _can_create(self, table):
self.dialect.validate_identifier(table.name)
if table.schema:
self.dialect.validate_identifier(table.schema)
return not self.checkfirst or not self.dialect.has_table(self.connection, table.name, schema=table.schema)
def visit_metadata(self, metadata):
if self.tables:
tables = self.tables
else:
tables = metadata.tables.values()
collection = [t for t in sql_util.sort_tables(tables) if self._can_create(t)]
for listener in metadata.ddl_listeners['before-create']:
listener('before-create', metadata, self.connection, tables=collection)
for table in collection:
self.traverse_single(table)
for listener in metadata.ddl_listeners['after-create']:
listener('after-create', metadata, self.connection, tables=collection)
def visit_table(self, table):
for listener in table.ddl_listeners['before-create']:
listener('before-create', table, self.connection)
for column in table.columns:
if column.default is not None:
self.traverse_single(column.default)
self.connection.execute(schema.CreateTable(table))
if hasattr(table, 'indexes'):
for index in table.indexes:
self.traverse_single(index)
for listener in table.ddl_listeners['after-create']:
listener('after-create', table, self.connection)
def visit_sequence(self, sequence):
if self.dialect.supports_sequences:
if ((not self.dialect.sequences_optional or
not sequence.optional) and
(not self.checkfirst or
not self.dialect.has_sequence(self.connection, sequence.name, schema=sequence.schema))):
self.connection.execute(schema.CreateSequence(sequence))
def visit_index(self, index):
self.connection.execute(schema.CreateIndex(index))
class SchemaDropper(DDLBase):
def __init__(self, dialect, connection, checkfirst=False, tables=None, **kwargs):
super(SchemaDropper, self).__init__(connection, **kwargs)
self.checkfirst = checkfirst
self.tables = tables
self.preparer = dialect.identifier_preparer
self.dialect = dialect
def visit_metadata(self, metadata):
if self.tables:
tables = self.tables
else:
tables = metadata.tables.values()
collection = [t for t in reversed(sql_util.sort_tables(tables)) if self._can_drop(t)]
for listener in metadata.ddl_listeners['before-drop']:
listener('before-drop', metadata, self.connection, tables=collection)
for table in collection:
self.traverse_single(table)
for listener in metadata.ddl_listeners['after-drop']:
listener('after-drop', metadata, self.connection, tables=collection)
def _can_drop(self, table):
self.dialect.validate_identifier(table.name)
if table.schema:
self.dialect.validate_identifier(table.schema)
return not self.checkfirst or self.dialect.has_table(self.connection, table.name, schema=table.schema)
def visit_index(self, index):
self.connection.execute(schema.DropIndex(index))
def visit_table(self, table):
for listener in table.ddl_listeners['before-drop']:
listener('before-drop', table, self.connection)
for column in table.columns:
if column.default is not None:
self.traverse_single(column.default)
self.connection.execute(schema.DropTable(table))
for listener in table.ddl_listeners['after-drop']:
listener('after-drop', table, self.connection)
def visit_sequence(self, sequence):
if self.dialect.supports_sequences:
if ((not self.dialect.sequences_optional or
not sequence.optional) and
(not self.checkfirst or
self.dialect.has_sequence(self.connection, sequence.name, schema=sequence.schema))):
self.connection.execute(schema.DropSequence(sequence))
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