Current File : //opt/alt/python37/lib/python3.7/site-packages/alembic/ddl/impl.py
from sqlalchemy import schema, text
from sqlalchemy import types as sqltypes
from ..util.compat import (
string_types, text_type, with_metaclass
)
from ..util import sqla_compat
from .. import util
from . import base
class ImplMeta(type):
def __init__(cls, classname, bases, dict_):
newtype = type.__init__(cls, classname, bases, dict_)
if '__dialect__' in dict_:
_impls[dict_['__dialect__']] = cls
return newtype
_impls = {}
class DefaultImpl(with_metaclass(ImplMeta)):
"""Provide the entrypoint for major migration operations,
including database-specific behavioral variances.
While individual SQL/DDL constructs already provide
for database-specific implementations, variances here
allow for entirely different sequences of operations
to take place for a particular migration, such as
SQL Server's special 'IDENTITY INSERT' step for
bulk inserts.
"""
__dialect__ = 'default'
transactional_ddl = False
command_terminator = ";"
def __init__(self, dialect, connection, as_sql,
transactional_ddl, output_buffer,
context_opts):
self.dialect = dialect
self.connection = connection
self.as_sql = as_sql
self.literal_binds = context_opts.get('literal_binds', False)
if self.literal_binds and not util.sqla_08:
util.warn("'literal_binds' flag not supported in SQLAlchemy 0.7")
self.literal_binds = False
self.output_buffer = output_buffer
self.memo = {}
self.context_opts = context_opts
if transactional_ddl is not None:
self.transactional_ddl = transactional_ddl
if self.literal_binds:
if not self.as_sql:
raise util.CommandError(
"Can't use literal_binds setting without as_sql mode")
@classmethod
def get_by_dialect(cls, dialect):
return _impls[dialect.name]
def static_output(self, text):
self.output_buffer.write(text_type(text + "\n\n"))
self.output_buffer.flush()
def requires_recreate_in_batch(self, batch_op):
"""Return True if the given :class:`.BatchOperationsImpl`
would need the table to be recreated and copied in order to
proceed.
Normally, only returns True on SQLite when operations other
than add_column are present.
"""
return False
def prep_table_for_batch(self, table):
"""perform any operations needed on a table before a new
one is created to replace it in batch mode.
the PG dialect uses this to drop constraints on the table
before the new one uses those same names.
"""
@property
def bind(self):
return self.connection
def _exec(self, construct, execution_options=None,
multiparams=(),
params=util.immutabledict()):
if isinstance(construct, string_types):
construct = text(construct)
if self.as_sql:
if multiparams or params:
# TODO: coverage
raise Exception("Execution arguments not allowed with as_sql")
if self.literal_binds and not isinstance(
construct, schema.DDLElement):
compile_kw = dict(compile_kwargs={"literal_binds": True})
else:
compile_kw = {}
self.static_output(text_type(
construct.compile(dialect=self.dialect, **compile_kw)
).replace("\t", " ").strip() + self.command_terminator)
else:
conn = self.connection
if execution_options:
conn = conn.execution_options(**execution_options)
return conn.execute(construct, *multiparams, **params)
def execute(self, sql, execution_options=None):
self._exec(sql, execution_options)
def alter_column(self, table_name, column_name,
nullable=None,
server_default=False,
name=None,
type_=None,
schema=None,
autoincrement=None,
existing_type=None,
existing_server_default=None,
existing_nullable=None,
existing_autoincrement=None
):
if autoincrement is not None or existing_autoincrement is not None:
util.warn(
"autoincrement and existing_autoincrement "
"only make sense for MySQL")
if nullable is not None:
self._exec(base.ColumnNullable(
table_name, column_name,
nullable, schema=schema,
existing_type=existing_type,
existing_server_default=existing_server_default,
existing_nullable=existing_nullable,
))
if server_default is not False:
self._exec(base.ColumnDefault(
table_name, column_name, server_default,
schema=schema,
existing_type=existing_type,
existing_server_default=existing_server_default,
existing_nullable=existing_nullable,
))
if type_ is not None:
self._exec(base.ColumnType(
table_name, column_name, type_, schema=schema,
existing_type=existing_type,
existing_server_default=existing_server_default,
existing_nullable=existing_nullable,
))
# do the new name last ;)
if name is not None:
self._exec(base.ColumnName(
table_name, column_name, name, schema=schema,
existing_type=existing_type,
existing_server_default=existing_server_default,
existing_nullable=existing_nullable,
))
def add_column(self, table_name, column, schema=None):
self._exec(base.AddColumn(table_name, column, schema=schema))
def drop_column(self, table_name, column, schema=None, **kw):
self._exec(base.DropColumn(table_name, column, schema=schema))
def add_constraint(self, const):
if const._create_rule is None or \
const._create_rule(self):
self._exec(schema.AddConstraint(const))
def drop_constraint(self, const):
self._exec(schema.DropConstraint(const))
def rename_table(self, old_table_name, new_table_name, schema=None):
self._exec(base.RenameTable(old_table_name,
new_table_name, schema=schema))
def create_table(self, table):
if util.sqla_07:
table.dispatch.before_create(table, self.connection,
checkfirst=False,
_ddl_runner=self)
self._exec(schema.CreateTable(table))
if util.sqla_07:
table.dispatch.after_create(table, self.connection,
checkfirst=False,
_ddl_runner=self)
for index in table.indexes:
self._exec(schema.CreateIndex(index))
def drop_table(self, table):
self._exec(schema.DropTable(table))
def create_index(self, index):
self._exec(schema.CreateIndex(index))
def drop_index(self, index):
self._exec(schema.DropIndex(index))
def bulk_insert(self, table, rows, multiinsert=True):
if not isinstance(rows, list):
raise TypeError("List expected")
elif rows and not isinstance(rows[0], dict):
raise TypeError("List of dictionaries expected")
if self.as_sql:
for row in rows:
self._exec(table.insert(inline=True).values(**dict(
(k,
sqla_compat._literal_bindparam(
k, v, type_=table.c[k].type)
if not isinstance(
v, sqla_compat._literal_bindparam) else v)
for k, v in row.items()
)))
else:
# work around http://www.sqlalchemy.org/trac/ticket/2461
if not hasattr(table, '_autoincrement_column'):
table._autoincrement_column = None
if rows:
if multiinsert:
self._exec(table.insert(inline=True), multiparams=rows)
else:
for row in rows:
self._exec(table.insert(inline=True).values(**row))
def compare_type(self, inspector_column, metadata_column):
conn_type = inspector_column.type
metadata_type = metadata_column.type
metadata_impl = metadata_type.dialect_impl(self.dialect)
# work around SQLAlchemy bug "stale value for type affinity"
# fixed in 0.7.4
metadata_impl.__dict__.pop('_type_affinity', None)
if hasattr(metadata_impl, "compare_against_backend"):
comparison = metadata_impl.compare_against_backend(
self.dialect, conn_type)
if comparison is not None:
return not comparison
if conn_type._compare_type_affinity(
metadata_impl
):
comparator = _type_comparators.get(conn_type._type_affinity, None)
return comparator and comparator(metadata_type, conn_type)
else:
return True
def compare_server_default(self, inspector_column,
metadata_column,
rendered_metadata_default,
rendered_inspector_default):
return rendered_inspector_default != rendered_metadata_default
def correct_for_autogen_constraints(self, conn_uniques, conn_indexes,
metadata_unique_constraints,
metadata_indexes):
pass
def _compat_autogen_column_reflect(self, inspector):
if util.sqla_08:
return self.autogen_column_reflect
else:
def adapt(table, column_info):
return self.autogen_column_reflect(
inspector, table, column_info)
return adapt
def correct_for_autogen_foreignkeys(self, conn_fks, metadata_fks):
pass
def autogen_column_reflect(self, inspector, table, column_info):
"""A hook that is attached to the 'column_reflect' event for when
a Table is reflected from the database during the autogenerate
process.
Dialects can elect to modify the information gathered here.
"""
def start_migrations(self):
"""A hook called when :meth:`.EnvironmentContext.run_migrations`
is called.
Implementations can set up per-migration-run state here.
"""
def emit_begin(self):
"""Emit the string ``BEGIN``, or the backend-specific
equivalent, on the current connection context.
This is used in offline mode and typically
via :meth:`.EnvironmentContext.begin_transaction`.
"""
self.static_output("BEGIN" + self.command_terminator)
def emit_commit(self):
"""Emit the string ``COMMIT``, or the backend-specific
equivalent, on the current connection context.
This is used in offline mode and typically
via :meth:`.EnvironmentContext.begin_transaction`.
"""
self.static_output("COMMIT" + self.command_terminator)
def _string_compare(t1, t2):
return \
t1.length is not None and \
t1.length != t2.length
def _numeric_compare(t1, t2):
return \
(
t1.precision is not None and
t1.precision != t2.precision
) or \
(
t1.scale is not None and
t1.scale != t2.scale
)
_type_comparators = {
sqltypes.String: _string_compare,
sqltypes.Numeric: _numeric_compare
}
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