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"""
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Extensions to SQLAlchemy for altering existing tables.
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At the moment, this isn't so much based off of ANSI as much as
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things that just happen to work with multiple databases.
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"""
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import StringIO
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import sqlalchemy as sa
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from sqlalchemy.schema import SchemaVisitor
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from sqlalchemy.engine.default import DefaultDialect
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from sqlalchemy.sql import ClauseElement
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from sqlalchemy.schema import (ForeignKeyConstraint,
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PrimaryKeyConstraint,
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CheckConstraint,
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UniqueConstraint,
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Index)
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from rhodecode.lib.dbmigrate.migrate import exceptions
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from rhodecode.lib.dbmigrate.migrate.changeset import constraint
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from sqlalchemy.schema import AddConstraint, DropConstraint
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from sqlalchemy.sql.compiler import DDLCompiler
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SchemaGenerator = SchemaDropper = DDLCompiler
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class AlterTableVisitor(SchemaVisitor):
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"""Common operations for ``ALTER TABLE`` statements."""
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# engine.Compiler looks for .statement
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# when it spawns off a new compiler
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statement = ClauseElement()
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def append(self, s):
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"""Append content to the SchemaIterator's query buffer."""
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self.buffer.write(s)
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def execute(self):
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"""Execute the contents of the SchemaIterator's buffer."""
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try:
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return self.connection.execute(self.buffer.getvalue())
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finally:
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self.buffer.truncate(0)
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def __init__(self, dialect, connection, **kw):
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self.connection = connection
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self.buffer = StringIO.StringIO()
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self.preparer = dialect.identifier_preparer
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self.dialect = dialect
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def traverse_single(self, elem):
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ret = super(AlterTableVisitor, self).traverse_single(elem)
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if ret:
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# adapt to 0.6 which uses a string-returning
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# object
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self.append(" %s" % ret)
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def _to_table(self, param):
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"""Returns the table object for the given param object."""
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if isinstance(param, (sa.Column, sa.Index, sa.schema.Constraint)):
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ret = param.table
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else:
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ret = param
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return ret
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def start_alter_table(self, param):
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"""Returns the start of an ``ALTER TABLE`` SQL-Statement.
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Use the param object to determine the table name and use it
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for building the SQL statement.
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:param param: object to determine the table from
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:type param: :class:`sqlalchemy.Column`, :class:`sqlalchemy.Index`,
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:class:`sqlalchemy.schema.Constraint`, :class:`sqlalchemy.Table`,
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or string (table name)
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"""
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table = self._to_table(param)
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self.append('\nALTER TABLE %s ' % self.preparer.format_table(table))
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return table
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class ANSIColumnGenerator(AlterTableVisitor, SchemaGenerator):
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"""Extends ansisql generator for column creation (alter table add col)"""
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def visit_column(self, column):
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"""Create a column (table already exists).
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:param column: column object
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:type column: :class:`sqlalchemy.Column` instance
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"""
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if column.default is not None:
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self.traverse_single(column.default)
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table = self.start_alter_table(column)
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self.append("ADD ")
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self.append(self.get_column_specification(column))
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for cons in column.constraints:
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self.traverse_single(cons)
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self.execute()
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# ALTER TABLE STATEMENTS
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# add indexes and unique constraints
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if column.index_name:
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Index(column.index_name,column).create()
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elif column.unique_name:
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constraint.UniqueConstraint(column,
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name=column.unique_name).create()
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# SA bounds FK constraints to table, add manually
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for fk in column.foreign_keys:
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self.add_foreignkey(fk.constraint)
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# add primary key constraint if needed
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if column.primary_key_name:
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cons = constraint.PrimaryKeyConstraint(column,
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name=column.primary_key_name)
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cons.create()
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def add_foreignkey(self, fk):
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self.connection.execute(AddConstraint(fk))
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class ANSIColumnDropper(AlterTableVisitor, SchemaDropper):
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"""Extends ANSI SQL dropper for column dropping (``ALTER TABLE
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DROP COLUMN``).
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"""
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def visit_column(self, column):
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"""Drop a column from its table.
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:param column: the column object
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:type column: :class:`sqlalchemy.Column`
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"""
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table = self.start_alter_table(column)
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self.append('DROP COLUMN %s' % self.preparer.format_column(column))
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self.execute()
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class ANSISchemaChanger(AlterTableVisitor, SchemaGenerator):
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"""Manages changes to existing schema elements.
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Note that columns are schema elements; ``ALTER TABLE ADD COLUMN``
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is in SchemaGenerator.
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All items may be renamed. Columns can also have many of their properties -
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type, for example - changed.
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Each function is passed a tuple, containing (object, name); where
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object is a type of object you'd expect for that function
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(ie. table for visit_table) and name is the object's new
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name. NONE means the name is unchanged.
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"""
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def visit_table(self, table):
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"""Rename a table. Other ops aren't supported."""
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self.start_alter_table(table)
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self.append("RENAME TO %s" % self.preparer.quote(table.new_name,
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table.quote))
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self.execute()
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def visit_index(self, index):
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"""Rename an index"""
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if hasattr(self, '_validate_identifier'):
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# SA <= 0.6.3
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self.append("ALTER INDEX %s RENAME TO %s" % (
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self.preparer.quote(
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self._validate_identifier(
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index.name, True), index.quote),
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self.preparer.quote(
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self._validate_identifier(
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index.new_name, True), index.quote)))
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else:
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# SA >= 0.6.5
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self.append("ALTER INDEX %s RENAME TO %s" % (
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self.preparer.quote(
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self._index_identifier(
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index.name), index.quote),
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self.preparer.quote(
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self._index_identifier(
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index.new_name), index.quote)))
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self.execute()
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def visit_column(self, delta):
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"""Rename/change a column."""
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# ALTER COLUMN is implemented as several ALTER statements
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keys = delta.keys()
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if 'type' in keys:
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self._run_subvisit(delta, self._visit_column_type)
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if 'nullable' in keys:
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self._run_subvisit(delta, self._visit_column_nullable)
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if 'server_default' in keys:
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# Skip 'default': only handle server-side defaults, others
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# are managed by the app, not the db.
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self._run_subvisit(delta, self._visit_column_default)
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if 'name' in keys:
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self._run_subvisit(delta, self._visit_column_name, start_alter=False)
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def _run_subvisit(self, delta, func, start_alter=True):
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"""Runs visit method based on what needs to be changed on column"""
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table = self._to_table(delta.table)
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col_name = delta.current_name
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if start_alter:
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self.start_alter_column(table, col_name)
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ret = func(table, delta.result_column, delta)
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self.execute()
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def start_alter_column(self, table, col_name):
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"""Starts ALTER COLUMN"""
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self.start_alter_table(table)
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self.append("ALTER COLUMN %s " % self.preparer.quote(col_name, table.quote))
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def _visit_column_nullable(self, table, column, delta):
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nullable = delta['nullable']
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if nullable:
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self.append("DROP NOT NULL")
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else:
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self.append("SET NOT NULL")
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def _visit_column_default(self, table, column, delta):
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default_text = self.get_column_default_string(column)
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if default_text is not None:
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self.append("SET DEFAULT %s" % default_text)
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else:
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self.append("DROP DEFAULT")
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def _visit_column_type(self, table, column, delta):
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type_ = delta['type']
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type_text = str(type_.compile(dialect=self.dialect))
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self.append("TYPE %s" % type_text)
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def _visit_column_name(self, table, column, delta):
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self.start_alter_table(table)
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col_name = self.preparer.quote(delta.current_name, table.quote)
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new_name = self.preparer.format_column(delta.result_column)
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self.append('RENAME COLUMN %s TO %s' % (col_name, new_name))
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class ANSIConstraintCommon(AlterTableVisitor):
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"""
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Migrate's constraints require a separate creation function from
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SA's: Migrate's constraints are created independently of a table;
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SA's are created at the same time as the table.
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"""
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def get_constraint_name(self, cons):
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"""Gets a name for the given constraint.
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If the name is already set it will be used otherwise the
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constraint's :meth:`autoname <migrate.changeset.constraint.ConstraintChangeset.autoname>`
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method is used.
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:param cons: constraint object
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"""
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if cons.name is not None:
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ret = cons.name
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else:
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ret = cons.name = cons.autoname()
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return self.preparer.quote(ret, cons.quote)
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def visit_migrate_primary_key_constraint(self, *p, **k):
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self._visit_constraint(*p, **k)
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def visit_migrate_foreign_key_constraint(self, *p, **k):
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self._visit_constraint(*p, **k)
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def visit_migrate_check_constraint(self, *p, **k):
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self._visit_constraint(*p, **k)
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def visit_migrate_unique_constraint(self, *p, **k):
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self._visit_constraint(*p, **k)
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class ANSIConstraintGenerator(ANSIConstraintCommon, SchemaGenerator):
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def _visit_constraint(self, constraint):
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constraint.name = self.get_constraint_name(constraint)
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self.append(self.process(AddConstraint(constraint)))
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self.execute()
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class ANSIConstraintDropper(ANSIConstraintCommon, SchemaDropper):
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def _visit_constraint(self, constraint):
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constraint.name = self.get_constraint_name(constraint)
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self.append(self.process(DropConstraint(constraint, cascade=constraint.cascade)))
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self.execute()
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class ANSIDialect(DefaultDialect):
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columngenerator = ANSIColumnGenerator
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columndropper = ANSIColumnDropper
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schemachanger = ANSISchemaChanger
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constraintgenerator = ANSIConstraintGenerator
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constraintdropper = ANSIConstraintDropper
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