561 lines
23 KiB
Python
561 lines
23 KiB
Python
import copy
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from decimal import Decimal
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from django.apps.registry import Apps
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from django.db import NotSupportedError
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from django.db.backends.base.schema import BaseDatabaseSchemaEditor
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from django.db.backends.ddl_references import Statement
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from django.db.backends.utils import strip_quotes
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from django.db.models import UniqueConstraint
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from django.db.transaction import atomic
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class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
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sql_delete_table = "DROP TABLE %(table)s"
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sql_create_fk = None
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sql_create_inline_fk = (
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"REFERENCES %(to_table)s (%(to_column)s) DEFERRABLE INITIALLY DEFERRED"
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)
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sql_create_column_inline_fk = sql_create_inline_fk
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sql_delete_column = "ALTER TABLE %(table)s DROP COLUMN %(column)s"
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sql_create_unique = "CREATE UNIQUE INDEX %(name)s ON %(table)s (%(columns)s)"
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sql_delete_unique = "DROP INDEX %(name)s"
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def __enter__(self):
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# Some SQLite schema alterations need foreign key constraints to be
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# disabled. Enforce it here for the duration of the schema edition.
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if not self.connection.disable_constraint_checking():
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raise NotSupportedError(
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"SQLite schema editor cannot be used while foreign key "
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"constraint checks are enabled. Make sure to disable them "
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"before entering a transaction.atomic() context because "
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"SQLite does not support disabling them in the middle of "
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"a multi-statement transaction."
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)
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return super().__enter__()
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def __exit__(self, exc_type, exc_value, traceback):
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self.connection.check_constraints()
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super().__exit__(exc_type, exc_value, traceback)
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self.connection.enable_constraint_checking()
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def quote_value(self, value):
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# The backend "mostly works" without this function and there are use
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# cases for compiling Python without the sqlite3 libraries (e.g.
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# security hardening).
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try:
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import sqlite3
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value = sqlite3.adapt(value)
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except ImportError:
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pass
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except sqlite3.ProgrammingError:
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pass
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# Manual emulation of SQLite parameter quoting
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if isinstance(value, bool):
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return str(int(value))
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elif isinstance(value, (Decimal, float, int)):
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return str(value)
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elif isinstance(value, str):
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return "'%s'" % value.replace("'", "''")
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elif value is None:
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return "NULL"
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elif isinstance(value, (bytes, bytearray, memoryview)):
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# Bytes are only allowed for BLOB fields, encoded as string
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# literals containing hexadecimal data and preceded by a single "X"
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# character.
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return "X'%s'" % value.hex()
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else:
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raise ValueError(
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"Cannot quote parameter value %r of type %s" % (value, type(value))
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)
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def prepare_default(self, value):
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return self.quote_value(value)
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def _is_referenced_by_fk_constraint(
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self, table_name, column_name=None, ignore_self=False
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):
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"""
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Return whether or not the provided table name is referenced by another
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one. If `column_name` is specified, only references pointing to that
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column are considered. If `ignore_self` is True, self-referential
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constraints are ignored.
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"""
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with self.connection.cursor() as cursor:
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for other_table in self.connection.introspection.get_table_list(cursor):
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if ignore_self and other_table.name == table_name:
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continue
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relations = self.connection.introspection.get_relations(
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cursor, other_table.name
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)
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for constraint_column, constraint_table in relations.values():
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if constraint_table == table_name and (
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column_name is None or constraint_column == column_name
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):
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return True
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return False
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def alter_db_table(
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self, model, old_db_table, new_db_table, disable_constraints=True
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):
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if (
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not self.connection.features.supports_atomic_references_rename
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and disable_constraints
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and self._is_referenced_by_fk_constraint(old_db_table)
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):
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if self.connection.in_atomic_block:
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raise NotSupportedError(
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(
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"Renaming the %r table while in a transaction is not "
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"supported on SQLite < 3.26 because it would break referential "
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"integrity. Try adding `atomic = False` to the Migration class."
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)
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% old_db_table
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)
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self.connection.enable_constraint_checking()
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super().alter_db_table(model, old_db_table, new_db_table)
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self.connection.disable_constraint_checking()
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else:
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super().alter_db_table(model, old_db_table, new_db_table)
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def alter_field(self, model, old_field, new_field, strict=False):
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if not self._field_should_be_altered(old_field, new_field):
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return
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old_field_name = old_field.name
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table_name = model._meta.db_table
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_, old_column_name = old_field.get_attname_column()
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if (
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new_field.name != old_field_name
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and not self.connection.features.supports_atomic_references_rename
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and self._is_referenced_by_fk_constraint(
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table_name, old_column_name, ignore_self=True
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)
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):
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if self.connection.in_atomic_block:
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raise NotSupportedError(
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(
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"Renaming the %r.%r column while in a transaction is not "
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"supported on SQLite < 3.26 because it would break referential "
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"integrity. Try adding `atomic = False` to the Migration class."
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)
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% (model._meta.db_table, old_field_name)
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)
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with atomic(self.connection.alias):
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super().alter_field(model, old_field, new_field, strict=strict)
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# Follow SQLite's documented procedure for performing changes
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# that don't affect the on-disk content.
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# https://sqlite.org/lang_altertable.html#otheralter
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with self.connection.cursor() as cursor:
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schema_version = cursor.execute("PRAGMA schema_version").fetchone()[
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0
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]
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cursor.execute("PRAGMA writable_schema = 1")
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references_template = ' REFERENCES "%s" ("%%s") ' % table_name
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new_column_name = new_field.get_attname_column()[1]
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search = references_template % old_column_name
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replacement = references_template % new_column_name
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cursor.execute(
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"UPDATE sqlite_master SET sql = replace(sql, %s, %s)",
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(search, replacement),
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)
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cursor.execute("PRAGMA schema_version = %d" % (schema_version + 1))
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cursor.execute("PRAGMA writable_schema = 0")
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# The integrity check will raise an exception and rollback
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# the transaction if the sqlite_master updates corrupt the
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# database.
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cursor.execute("PRAGMA integrity_check")
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# Perform a VACUUM to refresh the database representation from
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# the sqlite_master table.
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with self.connection.cursor() as cursor:
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cursor.execute("VACUUM")
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else:
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super().alter_field(model, old_field, new_field, strict=strict)
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def _remake_table(
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self, model, create_field=None, delete_field=None, alter_field=None
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):
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"""
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Shortcut to transform a model from old_model into new_model
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This follows the correct procedure to perform non-rename or column
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addition operations based on SQLite's documentation
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https://www.sqlite.org/lang_altertable.html#caution
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The essential steps are:
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1. Create a table with the updated definition called "new__app_model"
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2. Copy the data from the existing "app_model" table to the new table
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3. Drop the "app_model" table
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4. Rename the "new__app_model" table to "app_model"
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5. Restore any index of the previous "app_model" table.
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"""
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# Self-referential fields must be recreated rather than copied from
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# the old model to ensure their remote_field.field_name doesn't refer
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# to an altered field.
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def is_self_referential(f):
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return f.is_relation and f.remote_field.model is model
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# Work out the new fields dict / mapping
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body = {
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f.name: f.clone() if is_self_referential(f) else f
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for f in model._meta.local_concrete_fields
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}
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# Since mapping might mix column names and default values,
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# its values must be already quoted.
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mapping = {
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f.column: self.quote_name(f.column)
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for f in model._meta.local_concrete_fields
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}
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# This maps field names (not columns) for things like unique_together
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rename_mapping = {}
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# If any of the new or altered fields is introducing a new PK,
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# remove the old one
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restore_pk_field = None
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if getattr(create_field, "primary_key", False) or (
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alter_field and getattr(alter_field[1], "primary_key", False)
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):
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for name, field in list(body.items()):
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if field.primary_key and not (
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# Do not remove the old primary key when an altered field
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# that introduces a primary key is the same field.
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alter_field
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and name == alter_field[1].name
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):
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field.primary_key = False
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restore_pk_field = field
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if field.auto_created:
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del body[name]
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del mapping[field.column]
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# Add in any created fields
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if create_field:
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body[create_field.name] = create_field
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# Choose a default and insert it into the copy map
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if not create_field.many_to_many and create_field.concrete:
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mapping[create_field.column] = self.prepare_default(
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self.effective_default(create_field),
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)
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# Add in any altered fields
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if alter_field:
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old_field, new_field = alter_field
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body.pop(old_field.name, None)
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mapping.pop(old_field.column, None)
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body[new_field.name] = new_field
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if old_field.null and not new_field.null:
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case_sql = "coalesce(%(col)s, %(default)s)" % {
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"col": self.quote_name(old_field.column),
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"default": self.prepare_default(self.effective_default(new_field)),
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}
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mapping[new_field.column] = case_sql
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else:
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mapping[new_field.column] = self.quote_name(old_field.column)
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rename_mapping[old_field.name] = new_field.name
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# Remove any deleted fields
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if delete_field:
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del body[delete_field.name]
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del mapping[delete_field.column]
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# Remove any implicit M2M tables
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if (
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delete_field.many_to_many
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and delete_field.remote_field.through._meta.auto_created
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):
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return self.delete_model(delete_field.remote_field.through)
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# Work inside a new app registry
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apps = Apps()
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# Work out the new value of unique_together, taking renames into
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# account
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unique_together = [
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[rename_mapping.get(n, n) for n in unique]
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for unique in model._meta.unique_together
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]
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# Work out the new value for index_together, taking renames into
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# account
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index_together = [
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[rename_mapping.get(n, n) for n in index]
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for index in model._meta.index_together
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]
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indexes = model._meta.indexes
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if delete_field:
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indexes = [
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index for index in indexes if delete_field.name not in index.fields
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]
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constraints = list(model._meta.constraints)
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# Provide isolated instances of the fields to the new model body so
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# that the existing model's internals aren't interfered with when
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# the dummy model is constructed.
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body_copy = copy.deepcopy(body)
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# Construct a new model with the new fields to allow self referential
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# primary key to resolve to. This model won't ever be materialized as a
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# table and solely exists for foreign key reference resolution purposes.
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# This wouldn't be required if the schema editor was operating on model
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# states instead of rendered models.
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meta_contents = {
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"app_label": model._meta.app_label,
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"db_table": model._meta.db_table,
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"unique_together": unique_together,
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"index_together": index_together,
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"indexes": indexes,
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"constraints": constraints,
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"apps": apps,
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}
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meta = type("Meta", (), meta_contents)
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body_copy["Meta"] = meta
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body_copy["__module__"] = model.__module__
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type(model._meta.object_name, model.__bases__, body_copy)
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# Construct a model with a renamed table name.
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body_copy = copy.deepcopy(body)
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meta_contents = {
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"app_label": model._meta.app_label,
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"db_table": "new__%s" % strip_quotes(model._meta.db_table),
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"unique_together": unique_together,
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"index_together": index_together,
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"indexes": indexes,
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"constraints": constraints,
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"apps": apps,
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}
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meta = type("Meta", (), meta_contents)
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body_copy["Meta"] = meta
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body_copy["__module__"] = model.__module__
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new_model = type("New%s" % model._meta.object_name, model.__bases__, body_copy)
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# Create a new table with the updated schema.
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self.create_model(new_model)
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# Copy data from the old table into the new table
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self.execute(
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"INSERT INTO %s (%s) SELECT %s FROM %s"
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% (
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self.quote_name(new_model._meta.db_table),
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", ".join(self.quote_name(x) for x in mapping),
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", ".join(mapping.values()),
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self.quote_name(model._meta.db_table),
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)
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)
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# Delete the old table to make way for the new
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self.delete_model(model, handle_autom2m=False)
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# Rename the new table to take way for the old
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self.alter_db_table(
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new_model,
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new_model._meta.db_table,
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model._meta.db_table,
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disable_constraints=False,
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)
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# Run deferred SQL on correct table
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for sql in self.deferred_sql:
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self.execute(sql)
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self.deferred_sql = []
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# Fix any PK-removed field
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if restore_pk_field:
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restore_pk_field.primary_key = True
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def delete_model(self, model, handle_autom2m=True):
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if handle_autom2m:
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super().delete_model(model)
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else:
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# Delete the table (and only that)
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self.execute(
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self.sql_delete_table
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% {
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"table": self.quote_name(model._meta.db_table),
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}
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)
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# Remove all deferred statements referencing the deleted table.
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for sql in list(self.deferred_sql):
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if isinstance(sql, Statement) and sql.references_table(
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model._meta.db_table
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):
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self.deferred_sql.remove(sql)
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def add_field(self, model, field):
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"""Create a field on a model."""
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if (
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# Primary keys and unique fields are not supported in ALTER TABLE
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# ADD COLUMN.
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field.primary_key
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or field.unique
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or
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# Fields with default values cannot by handled by ALTER TABLE ADD
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# COLUMN statement because DROP DEFAULT is not supported in
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# ALTER TABLE.
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not field.null
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or self.effective_default(field) is not None
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):
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self._remake_table(model, create_field=field)
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else:
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super().add_field(model, field)
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def remove_field(self, model, field):
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"""
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Remove a field from a model. Usually involves deleting a column,
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but for M2Ms may involve deleting a table.
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"""
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# M2M fields are a special case
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if field.many_to_many:
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# For implicit M2M tables, delete the auto-created table
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if field.remote_field.through._meta.auto_created:
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self.delete_model(field.remote_field.through)
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# For explicit "through" M2M fields, do nothing
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elif (
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self.connection.features.can_alter_table_drop_column
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# Primary keys, unique fields, indexed fields, and foreign keys are
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# not supported in ALTER TABLE DROP COLUMN.
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and not field.primary_key
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and not field.unique
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and not field.db_index
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and not (field.remote_field and field.db_constraint)
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):
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super().remove_field(model, field)
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# For everything else, remake.
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else:
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# It might not actually have a column behind it
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if field.db_parameters(connection=self.connection)["type"] is None:
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return
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self._remake_table(model, delete_field=field)
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def _alter_field(
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self,
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model,
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old_field,
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new_field,
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old_type,
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new_type,
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old_db_params,
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new_db_params,
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strict=False,
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):
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"""Perform a "physical" (non-ManyToMany) field update."""
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# Use "ALTER TABLE ... RENAME COLUMN" if only the column name
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# changed and there aren't any constraints.
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if (
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self.connection.features.can_alter_table_rename_column
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and old_field.column != new_field.column
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and self.column_sql(model, old_field) == self.column_sql(model, new_field)
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and not (
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old_field.remote_field
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and old_field.db_constraint
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or new_field.remote_field
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and new_field.db_constraint
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)
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):
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return self.execute(
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self._rename_field_sql(
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model._meta.db_table, old_field, new_field, new_type
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)
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)
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# Alter by remaking table
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self._remake_table(model, alter_field=(old_field, new_field))
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# Rebuild tables with FKs pointing to this field.
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old_collation = old_db_params.get("collation")
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new_collation = new_db_params.get("collation")
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if new_field.unique and (
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old_type != new_type or old_collation != new_collation
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):
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related_models = set()
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opts = new_field.model._meta
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for remote_field in opts.related_objects:
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# Ignore self-relationship since the table was already rebuilt.
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if remote_field.related_model == model:
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continue
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if not remote_field.many_to_many:
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if remote_field.field_name == new_field.name:
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related_models.add(remote_field.related_model)
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elif new_field.primary_key and remote_field.through._meta.auto_created:
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related_models.add(remote_field.through)
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if new_field.primary_key:
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for many_to_many in opts.many_to_many:
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# Ignore self-relationship since the table was already rebuilt.
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if many_to_many.related_model == model:
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continue
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if many_to_many.remote_field.through._meta.auto_created:
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related_models.add(many_to_many.remote_field.through)
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for related_model in related_models:
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self._remake_table(related_model)
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def _alter_many_to_many(self, model, old_field, new_field, strict):
|
|
"""Alter M2Ms to repoint their to= endpoints."""
|
|
if (
|
|
old_field.remote_field.through._meta.db_table
|
|
== new_field.remote_field.through._meta.db_table
|
|
):
|
|
# The field name didn't change, but some options did, so we have to
|
|
# propagate this altering.
|
|
self._remake_table(
|
|
old_field.remote_field.through,
|
|
alter_field=(
|
|
# The field that points to the target model is needed, so
|
|
# we can tell alter_field to change it - this is
|
|
# m2m_reverse_field_name() (as opposed to m2m_field_name(),
|
|
# which points to our model).
|
|
old_field.remote_field.through._meta.get_field(
|
|
old_field.m2m_reverse_field_name()
|
|
),
|
|
new_field.remote_field.through._meta.get_field(
|
|
new_field.m2m_reverse_field_name()
|
|
),
|
|
),
|
|
)
|
|
return
|
|
|
|
# Make a new through table
|
|
self.create_model(new_field.remote_field.through)
|
|
# Copy the data across
|
|
self.execute(
|
|
"INSERT INTO %s (%s) SELECT %s FROM %s"
|
|
% (
|
|
self.quote_name(new_field.remote_field.through._meta.db_table),
|
|
", ".join(
|
|
[
|
|
"id",
|
|
new_field.m2m_column_name(),
|
|
new_field.m2m_reverse_name(),
|
|
]
|
|
),
|
|
", ".join(
|
|
[
|
|
"id",
|
|
old_field.m2m_column_name(),
|
|
old_field.m2m_reverse_name(),
|
|
]
|
|
),
|
|
self.quote_name(old_field.remote_field.through._meta.db_table),
|
|
)
|
|
)
|
|
# Delete the old through table
|
|
self.delete_model(old_field.remote_field.through)
|
|
|
|
def add_constraint(self, model, constraint):
|
|
if isinstance(constraint, UniqueConstraint) and (
|
|
constraint.condition
|
|
or constraint.contains_expressions
|
|
or constraint.include
|
|
or constraint.deferrable
|
|
):
|
|
super().add_constraint(model, constraint)
|
|
else:
|
|
self._remake_table(model)
|
|
|
|
def remove_constraint(self, model, constraint):
|
|
if isinstance(constraint, UniqueConstraint) and (
|
|
constraint.condition
|
|
or constraint.contains_expressions
|
|
or constraint.include
|
|
or constraint.deferrable
|
|
):
|
|
super().remove_constraint(model, constraint)
|
|
else:
|
|
self._remake_table(model)
|
|
|
|
def _collate_sql(self, collation):
|
|
return "COLLATE " + collation
|