from __future__ import annotations
import re
from typing import Any
from typing import Dict
from typing import Optional
from typing import TYPE_CHECKING
from typing import Union
from sqlalchemy import cast
from sqlalchemy import JSON
from sqlalchemy import schema
from sqlalchemy import sql
from sqlalchemy.ext.compiler import compiles
from .base import alter_table
from .base import format_table_name
from .base import RenameTable
from .impl import DefaultImpl
from .. import util
if TYPE_CHECKING:
from sqlalchemy.engine.reflection import Inspector
from sqlalchemy.sql.compiler import DDLCompiler
from sqlalchemy.sql.elements import Cast
from sqlalchemy.sql.elements import ClauseElement
from sqlalchemy.sql.schema import Column
from sqlalchemy.sql.schema import Constraint
from sqlalchemy.sql.schema import Table
from sqlalchemy.sql.type_api import TypeEngine
from ..operations.batch import BatchOperationsImpl
class SQLiteImpl(DefaultImpl):
__dialect__ = "sqlite"
transactional_ddl = False
"""SQLite supports transactional DDL, but pysqlite does not:
see: http://bugs.python.org/issue10740
"""
def requires_recreate_in_batch(
self, batch_op: BatchOperationsImpl
) -> bool:
"""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.
"""
for op in batch_op.batch:
if op[0] == "add_column":
col = op[1][1]
if isinstance(
col.server_default, schema.DefaultClause
) and isinstance(col.server_default.arg, sql.ClauseElement):
return True
elif (
isinstance(col.server_default, util.sqla_compat.Computed)
and col.server_default.persisted
):
return True
elif op[0] not in ("create_index", "drop_index"):
return True
else:
return False
def add_constraint(self, const: Constraint):
# attempt to distinguish between an
# auto-gen constraint and an explicit one
if const._create_rule is None: # type:ignore[attr-defined]
raise NotImplementedError(
"No support for ALTER of constraints in SQLite dialect. "
"Please refer to the batch mode feature which allows for "
"SQLite migrations using a copy-and-move strategy."
)
elif const._create_rule(self): # type:ignore[attr-defined]
util.warn(
"Skipping unsupported ALTER for "
"creation of implicit constraint. "
"Please refer to the batch mode feature which allows for "
"SQLite migrations using a copy-and-move strategy."
)
def drop_constraint(self, const: Constraint):
if const._create_rule is None: # type:ignore[attr-defined]
raise NotImplementedError(
"No support for ALTER of constraints in SQLite dialect. "
"Please refer to the batch mode feature which allows for "
"SQLite migrations using a copy-and-move strategy."
)
def compare_server_default(
self,
inspector_column: Column[Any],
metadata_column: Column[Any],
rendered_metadata_default: Optional[str],
rendered_inspector_default: Optional[str],
) -> bool:
if rendered_metadata_default is not None:
rendered_metadata_default = re.sub(
r"^\((.+)\)$", r"\1", rendered_metadata_default
)
rendered_metadata_default = re.sub(
r"^\"?'(.+)'\"?$", r"\1", rendered_metadata_default
)
if rendered_inspector_default is not None:
rendered_inspector_default = re.sub(
r"^\((.+)\)$", r"\1", rendered_inspector_default
)
rendered_inspector_default = re.sub(
r"^\"?'(.+)'\"?$", r"\1", rendered_inspector_default
)
return rendered_inspector_default != rendered_metadata_default
def _guess_if_default_is_unparenthesized_sql_expr(
self, expr: Optional[str]
) -> bool:
"""Determine if a server default is a SQL expression or a constant.
There are too many assertions that expect server defaults to round-trip
identically without parenthesis added so we will add parens only in
very specific cases.
"""
if not expr:
return False
elif re.match(r"^[0-9\.]$", expr):
return False
elif re.match(r"^'.+'$", expr):
return False
elif re.match(r"^\(.+\)$", expr):
return False
else:
return True
def autogen_column_reflect(
self,
inspector: Inspector,
table: Table,
column_info: Dict[str, Any],
) -> None:
# SQLite expression defaults require parenthesis when sent
# as DDL
if self._guess_if_default_is_unparenthesized_sql_expr(
column_info.get("default", None)
):
column_info["default"] = "(%s)" % (column_info["default"],)
def render_ddl_sql_expr(
self, expr: ClauseElement, is_server_default: bool = False, **kw
) -> str:
# SQLite expression defaults require parenthesis when sent
# as DDL
str_expr = super().render_ddl_sql_expr(
expr, is_server_default=is_server_default, **kw
)
if (
is_server_default
and self._guess_if_default_is_unparenthesized_sql_expr(str_expr)
):
str_expr = "(%s)" % (str_expr,)
return str_expr
def cast_for_batch_migrate(
self,
existing: Column[Any],
existing_transfer: Dict[str, Union[TypeEngine, Cast]],
new_type: TypeEngine,
) -> None:
if (
existing.type._type_affinity # type:ignore[attr-defined]
is not new_type._type_affinity # type:ignore[attr-defined]
and not isinstance(new_type, JSON)
):
existing_transfer["expr"] = cast(
existing_transfer["expr"], new_type
)
def correct_for_autogen_constraints(
self,
conn_unique_constraints,
conn_indexes,
metadata_unique_constraints,
metadata_indexes,
):
self._skip_functional_indexes(metadata_indexes, conn_indexes)
@compiles(RenameTable, "sqlite")
def visit_rename_table(
element: RenameTable, compiler: DDLCompiler, **kw
) -> str:
return "%s RENAME TO %s" % (
alter_table(compiler, element.table_name, element.schema),
format_table_name(compiler, element.new_table_name, None),
)
# @compiles(AddColumn, 'sqlite')
# def visit_add_column(element, compiler, **kw):
# return "%s %s" % (
# alter_table(compiler, element.table_name, element.schema),
# add_column(compiler, element.column, **kw)
# )
# def add_column(compiler, column, **kw):
# text = "ADD COLUMN %s" % compiler.get_column_specification(column, **kw)
# need to modify SQLAlchemy so that the CHECK associated with a Boolean
# or Enum gets placed as part of the column constraints, not the Table
# see ticket 98
# for const in column.constraints:
# text += compiler.process(AddConstraint(const))
# return text
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