sqlalchemy.events SchemaEventTarget Example Code

SchemaEventTarget is a class within the sqlalchemy.events module of the SQLAlchemy project.

Example 1 from alembic

Alembic (project documentation and PyPI page) is a data migrations tool used with SQLAlchemy to make database schema changes. The Alembic project is open sourced under the MIT license.

alembic / alembic / operations / batch.py

# batch.py
from sqlalchemy import CheckConstraint
from sqlalchemy import Column
from sqlalchemy import ForeignKeyConstraint
from sqlalchemy import Index
from sqlalchemy import MetaData
from sqlalchemy import PrimaryKeyConstraint
from sqlalchemy import schema as sql_schema
from sqlalchemy import select
from sqlalchemy import Table
from sqlalchemy import types as sqltypes
from sqlalchemy.events import SchemaEventTarget
from sqlalchemy.util import OrderedDict
from sqlalchemy.util import topological

from ..util import exc
from ..util.sqla_compat import _columns_for_constraint
from ..util.sqla_compat import _fk_is_self_referential
from ..util.sqla_compat import _is_type_bound
from ..util.sqla_compat import _remove_column_from_collection


class BatchOperationsImpl(object):
    def __init__(
        self,
        operations,
        table_name,
        schema,
        recreate,
        copy_from,
        table_args,
        table_kwargs,
        reflect_args,
        reflect_kwargs,
        naming_convention,
        partial_reordering,


## ... source file abbreviated to get to SchemaEventTarget examples ...


        self.table_kwargs = table_kwargs
        self.temp_table_name = self._calc_temp_name(table.name)
        self.new_table = None

        self.partial_reordering = partial_reordering  # tuple of tuples
        self.add_col_ordering = ()  # tuple of tuples

        self.column_transfers = OrderedDict(
            (c.name, {"expr": c}) for c in self.table.c
        )
        self.existing_ordering = list(self.column_transfers)

        self.reflected = reflected
        self._grab_table_elements()

    @classmethod
    def _calc_temp_name(cls, tablename):
        return ("_alembic_tmp_%s" % tablename)[0:50]

    def _grab_table_elements(self):
        schema = self.table.schema
        self.columns = OrderedDict()
        for c in self.table.c:
            c_copy = c.copy(schema=schema)
            c_copy.unique = c_copy.index = False
            if isinstance(c.type, SchemaEventTarget):
                assert c_copy.type is not c.type
            self.columns[c.name] = c_copy
        self.named_constraints = {}
        self.unnamed_constraints = []
        self.indexes = {}
        self.new_indexes = {}
        for const in self.table.constraints:
            if _is_type_bound(const):
                continue
            elif self.reflected and isinstance(const, CheckConstraint):
                pass
            elif const.name:
                self.named_constraints[const.name] = const
            else:
                self.unnamed_constraints.append(const)

        for idx in self.table.indexes:
            self.indexes[idx.name] = idx

        for k in self.table.kwargs:
            self.table_kwargs.setdefault(k, self.table.kwargs[k])

    def _adjust_self_columns_for_partial_reordering(self):
        pairs = set()


## ... source file abbreviated to get to SchemaEventTarget examples ...


            try:
                for idx in self._gather_indexes_from_both_tables():
                    op_impl.create_index(idx)
            finally:
                self.new_table.name = self.temp_table_name

    def alter_column(
        self,
        table_name,
        column_name,
        nullable=None,
        server_default=False,
        name=None,
        type_=None,
        autoincrement=None,
        **kw
    ):
        existing = self.columns[column_name]
        existing_transfer = self.column_transfers[column_name]
        if name is not None and name != column_name:
            existing.name = name
            existing_transfer["name"] = name

        if type_ is not None:
            type_ = sqltypes.to_instance(type_)
            if isinstance(existing.type, SchemaEventTarget):
                existing.type._create_events = (
                    existing.type.create_constraint
                ) = False

            self.impl.cast_for_batch_migrate(
                existing, existing_transfer, type_
            )

            existing.type = type_


        if nullable is not None:
            existing.nullable = nullable
        if server_default is not False:
            if server_default is None:
                existing.server_default = None
            else:
                sql_schema.DefaultClause(server_default)._set_parent(existing)
        if autoincrement is not None:
            existing.autoincrement = bool(autoincrement)

    def _setup_dependencies_for_add_column(
        self, colname, insert_before, insert_after
    ):


## ... source file continues with no further SchemaEventTarget examples...

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