the hacky ReassignBackupIdAction

Author: Fallen-Breath

prime_backup/action/reassign_backup_id_action.py

@@ -0,0 +1,26 @@
+import dataclasses
+from typing import Optional
+
+from typing_extensions import override
+
+from prime_backup.action import Action
+from prime_backup.db.access import DbAccess
+from prime_backup.types.backup_filter import BackupSortOrder
+
+
+@dataclasses.dataclass(frozen=True)
+class ReassignBackupIdResult:
+	max_id: Optional[int]
+
+
+class ReassignBackupIdAction(Action[ReassignBackupIdResult]):
+	def __init__(self, order: BackupSortOrder = BackupSortOrder.id):
+		super().__init__()
+		self.order = order
+
+	@override
+	def run(self) -> ReassignBackupIdResult:
+		with DbAccess.open_session() as session:
+			max_id = session.reassign_backup_id(self.order)
+		self.logger.info('Backup ID reassigned, current max Backup.id: {}'.format(max_id))
+		return ReassignBackupIdResult(max_id)

prime_backup/db/session.py

@@ -7,7 +7,7 @@
 from typing import Optional, Sequence, Dict, Iterator, Callable, Set, Generator, Iterable, Tuple, Any
 from typing import TypeVar, List
 
-from sqlalchemy import select, delete, desc, func, Select, JSON, text, or_, not_, and_, exists, Row
+from sqlalchemy import select, delete, desc, func, Select, JSON, text, or_, not_, and_, exists, Row, update
 from sqlalchemy.orm import Session
 from typing_extensions import overload, Union, TypedDict, Unpack, NotRequired
 
@@ -74,6 +74,11 @@ def __supports_json_query(cls) -> bool:
 	def __supports_vacuum_into(cls) -> bool:
 		return cls.__check_support(db_utils.check_sqlite_vacuum_into_support, 'SQLite backend does not support VACUUM INTO statement. Insecure manual file copy is used as the fallback')
 
+	@classmethod
+	@functools.lru_cache
+	def __supports_row_number(cls) -> bool:
+		return cls.__check_support(db_utils.check_sqlite_row_number, 'SQLite backend does not support ROW_NUMBER() statement, ID reassignment is not available')
+
 	@classmethod
 	def __validate_int_fields_range(cls, obj: schema.Base):
 		from sqlalchemy import Integer, BigInteger
@@ -1588,3 +1593,44 @@ def iterate_backup_batch(self, *, batch_size: int = 1000) -> Iterator[List[schem
 
 	def delete_backup(self, backup: schema.Backup):
 		self.session.delete(backup)
+
+	def reassign_backup_id(self, order: BackupSortOrder) -> Optional[int]:
+		if not self.__supports_row_number():
+			raise RuntimeError('Current SQLite version {} does not support ROW_NUMBER() function'.format(db_utils.get_sqlite_version()))
+
+		order_by: list
+		if order == BackupSortOrder.time:
+			order_by = [schema.Backup.timestamp, schema.Backup.timestamp_ns_part, schema.Backup.id]
+		elif order == BackupSortOrder.time_r:
+			order_by = [desc(schema.Backup.timestamp), desc(schema.Backup.timestamp_ns_part), desc(schema.Backup.id)]
+		elif order == BackupSortOrder.id:
+			order_by = [schema.Backup.id]
+		elif order == BackupSortOrder.id_r:
+			order_by = [desc(schema.Backup.id)]
+		else:
+			raise ValueError(order)
+
+		numbered_cte = select(
+			schema.Backup.id,
+			func.row_number().over(order_by=order_by).label('new_id')
+		).cte('numbered')
+		numbered_alias = numbered_cte.alias()
+		self.session.execute(
+			update(schema.Backup).
+			values(id=numbered_alias.c.new_id).
+			where(schema.Backup.id == numbered_alias.c.id)
+		)
+
+		max_id: Optional[int] = self.session.execute(select(func.max(schema.Backup.id))).scalar()
+		table_name = schema.Backup.__tablename__
+		if max_id is not None:
+			self.session.execute(
+				text(f'''UPDATE sqlite_sequence SET seq = :seq WHERE name = :name''').
+				bindparams(seq=max_id, name=table_name)
+			)
+		else:
+			self.session.execute(
+				text(f'''DELETE FROM sqlite_sequence WHERE name = :name''').
+				bindparams(name=table_name)
+			)
+		return max_id

prime_backup/utils/db_utils.py

@@ -1,6 +1,10 @@
 import sqlite3
 
 
+def get_sqlite_version() -> str:
+	return sqlite3.sqlite_version
+
+
 def check_sqlite_json_query_support() -> bool:
 	try:
 		with sqlite3.connect(':memory:') as conn:
@@ -18,7 +22,12 @@ def check_sqlite_vacuum_into_support() -> bool:
 	return sqlite3.sqlite_version_info >= (3, 27, 0)
 
 
+def check_sqlite_row_number() -> bool:
+	return sqlite3.sqlite_version_info >= (3, 25, 0)
+
+
 if __name__ == '__main__':
 	print('version:', sqlite3.sqlite_version)
 	print('json query:', check_sqlite_json_query_support())
 	print('vacuum into:', check_sqlite_vacuum_into_support())
+	print('row number:', check_sqlite_row_number())

prime_backup/utils/file_utils.py

@@ -92,7 +92,7 @@ def __get_copier():
 
 
 def copy_file_obj_fast(src: SupportsReadBytes, dst: SupportsWriteBytes, *, estimate_read_size: int = 0):
-	if estimate_read_size > 1048576 and False:  # TODO
+	if estimate_read_size > 1048576 and True:  # TODO
 		__get_copier().copy(src, dst)
 	else:
 		shutil.copyfileobj(src, dst)