# Copyright 2020 Google LLC
#
# Use of this source code is governed by a BSD-style
# license that can be found in the LICENSE file or at
# https://developers.google.com/open-source/licenses/bsd
import uuid
from django.db import NotSupportedError
from django.db.backends.base.schema import BaseDatabaseSchemaEditor
from django_spanner._opentelemetry_tracing import trace_call
from django_spanner import USE_EMULATOR, USING_DJANGO_3
[docs]class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
"""
The database abstraction layer that turns things like “create a model” or
“delete a field” into SQL.
"""
sql_create_table = (
"CREATE TABLE %(table)s (%(definition)s) PRIMARY KEY(%(primary_key)s)"
)
sql_delete_table = "DROP TABLE %(table)s"
sql_create_fk = None
# Spanner doesn't support partial indexes. This string omits the
# %(condition)s placeholder so that partial indexes are ignored.
sql_create_index = (
"CREATE INDEX %(name)s ON %(table)s%(using)s (%(columns)s)%(extra)s"
)
sql_create_unique = (
"CREATE UNIQUE NULL_FILTERED INDEX %(name)s ON %(table)s (%(columns)s)"
)
sql_delete_unique = "DROP INDEX %(name)s"
# Cloud Spanner requires when changing if a column is NULLABLE,
# that it should get redefined with its type and size.
# See
# https://cloud.google.com/spanner/docs/schema-updates#updates-that-require-validation # noqa
sql_alter_column_null = "ALTER COLUMN %(column)s %(type)s"
sql_alter_column_not_null = "ALTER COLUMN %(column)s %(type)s NOT NULL"
sql_alter_column_type = "ALTER COLUMN %(column)s %(type)s"
sql_delete_column = "ALTER TABLE %(table)s DROP COLUMN %(column)s"
# Spanner does not suppport ON DELETE CASCADE for foreign keys.
# This can cause failures in django, hence sql_create_inline_fk is disabled.
# sql_create_inline_fk = "CONSTRAINT FK_%(to_table)s_%(to_column)s_%(from_table)s_%(from_column)s FOREIGN KEY (%(from_column_norm)s) REFERENCES %(to_table_norm)s (%(to_column_norm)s)" # noqa
sql_create_inline_fk = None
[docs] def create_model(self, model):
"""
Create a table and any accompanying indexes or unique constraints for
the given `model`.
:type model: :class:`~django.db.migrations.operations.models.ModelOperation`
:param model: A model for creating a table.
"""
# Create column SQL, add FK deferreds if needed
column_sqls = []
params = []
for field in model._meta.local_fields:
# SQL
definition, extra_params = self.column_sql(model, field)
if definition is None:
continue
# Check constraints can go on the column SQL here
db_params = field.db_parameters(connection=self.connection)
if db_params["check"]:
definition += (
", CONSTRAINT constraint_%s_%s_%s "
% (
model._meta.db_table,
self.quote_name(field.name),
uuid.uuid4().hex[:6].lower(),
)
+ self.sql_check_constraint % db_params
)
# Autoincrement SQL (for backends with inline variant)
col_type_suffix = field.db_type_suffix(connection=self.connection)
if col_type_suffix:
definition += " %s" % col_type_suffix
params.extend(extra_params)
# FK
if field.remote_field and field.db_constraint:
from_table = field.model._meta.db_table
from_column = field.column
to_table = field.remote_field.model._meta.db_table
to_column = field.remote_field.model._meta.get_field(
field.remote_field.field_name
).column
if self.sql_create_inline_fk:
definition += ", " + self.sql_create_inline_fk % {
"from_table": from_table,
"from_column": from_column,
"to_table": to_table,
"to_column": to_column,
"from_column_norm": self.quote_name(from_column),
"to_table_norm": self.quote_name(to_table),
"to_column_norm": self.quote_name(to_column),
}
elif self.connection.features.supports_foreign_keys:
self.deferred_sql.append(
self._create_fk_sql(
model, field, "_fk_%(to_table)s_%(to_column)s"
)
)
# Add the SQL to our big list
column_sqls.append(
"%s %s" % (self.quote_name(field.column), definition)
)
# Create a unique constraint separately because Spanner doesn't
# allow them inline on a column.
if field.unique and not field.primary_key:
self.deferred_sql.append(
self._create_unique_sql(model, [field.column])
)
# Add any unique_togethers (always deferred, as some fields might be
# created afterwards, like geometry fields with some backends)
for fields in model._meta.unique_together:
columns = [model._meta.get_field(field).column for field in fields]
self.deferred_sql.append(self._create_unique_sql(model, columns))
constraints = [
constraint.constraint_sql(model, self)
for constraint in model._meta.constraints
]
# Make the table
sql = self.sql_create_table % {
"table": self.quote_name(model._meta.db_table),
"definition": ", ".join(
constraint
for constraint in (*column_sqls, *constraints)
if constraint
),
"primary_key": self.quote_name(model._meta.pk.column),
}
if model._meta.db_tablespace:
tablespace_sql = self.connection.ops.tablespace_sql(
model._meta.db_tablespace
)
if tablespace_sql:
sql += " " + tablespace_sql
# Prevent using [] as params, in the case a literal '%' is used in the
# definition
trace_attributes = {
"model_name": self.quote_name(model._meta.db_table)
}
with trace_call(
"CloudSpannerDjango.create_model",
self.connection,
trace_attributes,
):
self.execute(sql, params or None)
# Add any field index and index_together's (deferred as SQLite
# _remake_table needs it)
self.deferred_sql.extend(self._model_indexes_sql(model))
# Make M2M tables
for field in model._meta.local_many_to_many:
if field.remote_field.through._meta.auto_created:
self.create_model(field.remote_field.through)
[docs] def delete_model(self, model):
"""
Drop the model's table in the database along with any unique constraints
or indexes it has.
:type model: :class:`~django.db.migrations.operations.models.ModelOperation`
:param model: A model for creating a table.
"""
# Spanner requires dropping all of a table's indexes before dropping
# the table.
index_names = self._constraint_names(
model, index=True, primary_key=False
)
for index_name in index_names:
trace_attributes = {
"model_name": self.quote_name(model._meta.db_table),
"index_name": index_name,
}
with trace_call(
"CloudSpannerDjango.delete_model.delete_index",
self.connection,
trace_attributes,
):
self.execute(self._delete_index_sql(model, index_name))
trace_attributes = {
"model_name": self.quote_name(model._meta.db_table)
}
with trace_call(
"CloudSpannerDjango.delete_model",
self.connection,
trace_attributes,
):
super().delete_model(model)
[docs] def add_field(self, model, field):
"""
Add a column (or sometimes multiple) to the model's table to
represent the field. This will also add indexes or a unique constraint
if the field has db_index=True or unique=True. If the field is a
ManyToManyField without a value for through, instead of creating a
column, it will make a table to represent the relationship. If through
is provided, it is a no-op. If the field is a ForeignKey, this will
also add the foreign key constraint to the column.
:type model: :class:`~django.db.migrations.operations.models.ModelOperation`
:param model: A model for creating a table.
:type field: :class:`~django.db.migrations.operations.models.fields.FieldOperation`
:param field: The field of the table.
"""
# Special-case implicit M2M tables
if (
field.many_to_many
and field.remote_field.through._meta.auto_created
):
return self.create_model(field.remote_field.through)
# Get the column's definition
definition, params = self.column_sql(
model, field, exclude_not_null=True
)
# It might not actually have a column behind it
if definition is None:
return
# Check constraints can go on the column SQL here
db_params = field.db_parameters(connection=self.connection)
if db_params["check"]:
definition += (
", CONSTRAINT constraint_%s_%s_%s "
% (
model._meta.db_table,
self.quote_name(field.name),
uuid.uuid4().hex[:6].lower(),
)
+ self.sql_check_constraint % db_params
)
# Build the SQL and run it
sql = self.sql_create_column % {
"table": self.quote_name(model._meta.db_table),
"column": self.quote_name(field.column),
"definition": definition,
}
self.execute(sql, params)
# Set defaults values on existing rows. (Django usually uses-database
# defaults for this but Spanner doesn't support them.)
effective_default = self.effective_default(field)
if effective_default is not None:
self.execute(
"UPDATE %(table)s SET %(column)s=%%s"
% {
"table": self.quote_name(model._meta.db_table),
"column": self.quote_name(field.column),
},
(effective_default,),
)
# Spanner doesn't support adding NOT NULL columns to existing tables.
if not field.null:
self.execute(
self.sql_alter_column
% {
"table": self.quote_name(model._meta.db_table),
"changes": self.sql_alter_column_not_null
% {
"column": self.quote_name(field.column),
"type": db_params["type"],
},
}
)
# Add an index, if required
self.deferred_sql.extend(self._field_indexes_sql(model, field))
# Create a unique constraint separately because Spanner doesn't allow
# them inline on a column.
if field.unique and not field.primary_key:
self.deferred_sql.append(
self._create_unique_sql(model, [field.column])
)
# Add any FK constraints later
if (
field.remote_field
and self.connection.features.supports_foreign_keys
and field.db_constraint
):
self.deferred_sql.append(
self._create_fk_sql(
model, field, "_fk_%(to_table)s_%(to_column)s"
)
)
[docs] def remove_field(self, model, field):
"""
Remove the column(s) representing the field from the model's table,
along with any unique constraints, foreign key constraints, or indexes
caused by that field. If the field is a ManyToManyField without a
value for through, it will remove the table created to track the
relationship. If through is provided, it is a no-op.
:type model: :class:`~django.db.migrations.operations.models.ModelOperation`
:param model: A model for creating a table.
:type field: :class:`~django.db.migrations.operations.models.fields.FieldOperation`
:param field: The field of the table.
"""
# Spanner requires dropping a column's indexes before dropping the
# column.
index_names = self._constraint_names(model, [field.column], index=True)
for index_name in index_names:
trace_attributes = {
"model_name": self.quote_name(model._meta.db_table),
"field": field.column,
"index_name": index_name,
}
with trace_call(
"CloudSpannerDjango.remove_field.delete_index",
self.connection,
trace_attributes,
):
self.execute(self._delete_index_sql(model, index_name))
trace_attributes = {
"model_name": self.quote_name(model._meta.db_table),
"field": field.column,
}
with trace_call(
"CloudSpannerDjango.remove_field",
self.connection,
trace_attributes,
):
super().remove_field(model, field)
[docs] def column_sql(
self, model, field, include_default=False, exclude_not_null=False
):
"""
Take a field and return its column definition.
The field must already have had set_attributes_from_name() called.
:type model: :class:`~django.db.migrations.operations.models.ModelOperation`
:param model: A model for creating a table.
:type field: :class:`~django.db.migrations.operations.models.fields.FieldOperation`
:param field: The field of the table.
:type include_default: bool
:param include_default: (Optional) Flag for including default fields.
:type exclude_not_null: bool
:param exclude_not_null: (Optional) Flag for excluding not null fields.
"""
# Get the column's type and use that as the basis of the SQL
db_params = field.db_parameters(connection=self.connection)
sql = db_params["type"]
params = []
# Check for fields that aren't actually columns (e.g. M2M)
if sql is None:
return None, None
# Work out nullability
null = field.null
# Oracle treats the empty string ('') as null, so coerce the null
# option whenever '' is a possible value.
if (
field.empty_strings_allowed
and not field.primary_key
and self.connection.features.interprets_empty_strings_as_nulls
):
null = True
if not null and not exclude_not_null:
sql += " NOT NULL"
# Optionally add the tablespace if it's an implicitly indexed column
tablespace = field.db_tablespace or model._meta.db_tablespace
if (
tablespace
and self.connection.features.supports_tablespaces
and field.unique
):
sql += " %s" % self.connection.ops.tablespace_sql(
tablespace, inline=True
)
# Return the sql
return sql, params
[docs] def add_index(self, model, index):
"""Add index to model's table.
:type model: :class:`~django.db.migrations.operations.models.ModelOperation`
:param model: A model for creating a table.
:type index: :class:`~django.db.migrations.operations.models.Index`
:param index: An index to add.
"""
# Work around a bug in Django where a space isn't inserting before
# DESC: https://code.djangoproject.com/ticket/30961
# This method can be removed in Django 3.1.
index.fields_orders = [
(field_name, " DESC" if order == "DESC" else "")
for field_name, order in index.fields_orders
]
trace_attributes = {
"model_name": self.quote_name(model._meta.db_table),
"index": "|".join(index.fields),
}
with trace_call(
"CloudSpannerDjango.add_index",
self.connection,
trace_attributes,
):
super().add_index(model, index)
[docs] def quote_value(self, value):
# A more complete implementation isn't currently required.
if isinstance(value, str):
return "'%s'" % value.replace("'", "''")
return str(value)
def _alter_field(
self,
model,
old_field,
new_field,
old_type,
new_type,
old_db_params,
new_db_params,
strict=False,
):
# Spanner requires dropping indexes before changing the nullability
# of a column.
nullability_changed = old_field.null != new_field.null
if nullability_changed:
index_names = self._constraint_names(
model, [old_field.column], index=True
)
if index_names and not old_field.db_index:
raise NotSupportedError(
"Changing nullability of a field with an index other than "
"Field(db_index=True) isn't yet supported."
)
if len(index_names) > 1:
raise NotSupportedError(
"Changing nullability of a field with more than one "
"index isn't yet supported."
)
for index_name in index_names:
trace_attributes = {
"model_name": self.quote_name(model._meta.db_table),
"alter_field": old_field.column,
"index_name": index_name,
}
with trace_call(
"CloudSpannerDjango.alter_field.delete_index",
self.connection,
trace_attributes,
):
self.execute(self._delete_index_sql(model, index_name))
trace_attributes = {
"model_name": self.quote_name(model._meta.db_table),
"alter_field": old_field.column,
}
with trace_call(
"CloudSpannerDjango.alter_field",
self.connection,
trace_attributes,
):
super()._alter_field(
model,
old_field,
new_field,
old_type,
new_type,
old_db_params,
new_db_params,
strict=False,
)
# Recreate the index that was dropped earlier.
if nullability_changed and new_field.db_index:
trace_attributes = {
"model_name": self.quote_name(model._meta.db_table),
"alter_field": new_field.column,
}
with trace_call(
"CloudSpannerDjango.alter_field.recreate_index",
self.connection,
trace_attributes,
):
self.execute(self._create_index_sql(model, fields=[new_field]))
def _alter_column_type_sql(self, model, old_field, new_field, new_type):
# Spanner needs to use sql_alter_column_not_null if the field is
# NOT NULL, otherwise the constraint is dropped.
sql = (
self.sql_alter_column_type
if new_field.null
else self.sql_alter_column_not_null
)
return (
(
sql
% {
"column": self.quote_name(new_field.column),
"type": new_type,
},
[],
),
[],
)
def _check_sql(self, name, check):
# Emulator does not support check constraints yet.
if USE_EMULATOR:
return None
return self.sql_constraint % {
"name": self.quote_name(name),
"constraint": self.sql_check_constraint % {"check": check},
}
def _unique_sql(
self,
model,
fields,
name,
condition=None,
deferrable=None, # Spanner does not require this parameter
include=None,
opclasses=None,
):
# Inline constraints aren't supported, so create the index separately.
if USING_DJANGO_3:
sql = self._create_unique_sql(
model,
fields,
name=name,
condition=condition,
include=include,
opclasses=opclasses,
)
else:
sql = self._create_unique_sql(
model, fields, name=name, condition=condition
)
if sql:
self.deferred_sql.append(sql)
return None
[docs] def skip_default(self, field):
"""Cloud Spanner doesn't support column defaults."""
return True
