add DbSession.get_chunk_overview_stats to optimize GetDbOverviewAction on db with tons of chunks

Author: Fallen-Breath

prime_backup/action/get_db_overview_action.py

@@ -46,12 +46,13 @@ def run(self) -> DbOverviewResult:
 		with DbAccess.open_session() as session:
 			meta = session.get_db_meta()
 			blob_size_sums = session.get_blob_size_sums_by_storage_method()
+			chunk_stats = session.get_chunk_overview_stats()
 			return DbOverviewResult(
 				db_version=meta.version,
 				hash_method=meta.hash_method,
 
 				blob_count=session.get_blob_count(),
-				chunk_count=session.get_chunk_count(),
+				chunk_count=chunk_stats.count,
 				chunk_group_count=session.get_chunk_group_count(),
 				chunk_group_chunk_binding_count=session.get_chunk_group_chunk_binding_count(),
 				blob_chunk_group_binding_count=session.get_blob_chunk_group_binding_count(),
@@ -68,8 +69,8 @@ def run(self) -> DbOverviewResult:
 				chunked_blob_stored_size_sum=blob_size_sums[BlobStorageMethod.chunked].stored_size,
 				chunked_blob_raw_size_sum=blob_size_sums[BlobStorageMethod.chunked].raw_size,
 				chunked_blob_chunk_count=session.get_chunked_blob_chunk_count(),
-				chunk_raw_size_sum=session.get_chunk_raw_size_sum(),
-				chunk_stored_size_sum=session.get_chunk_stored_size_sum(),
+				chunk_raw_size_sum=chunk_stats.raw_size_sum,
+				chunk_stored_size_sum=chunk_stats.stored_size_sum,
 				file_raw_size_sum=session.get_file_total_raw_size_sum(),
 
 				db_file_size=db_file_size,

prime_backup/db/session.py

@@ -431,6 +431,24 @@ def get_chunk_raw_size_sum(self) -> int:
 	def get_chunk_stored_size_sum(self) -> int:
 		return _int_or_0(self.session.execute(func.sum(schema.Chunk.stored_size).select()).scalar_one())
 
+	@dataclasses.dataclass(frozen=True)
+	class ChunkOverviewStats:
+		count: int
+		stored_size_sum: int
+		raw_size_sum: int
+
+	def get_chunk_overview_stats(self) -> ChunkOverviewStats:
+		count, stored_size_sum, raw_size_sum = self.session.execute(select(
+			func.count(schema.Chunk.id),
+			func.sum(schema.Chunk.stored_size),
+			func.sum(schema.Chunk.raw_size)
+		)).one()
+		return self.ChunkOverviewStats(
+			count=_int_or_0(count),
+			stored_size_sum=_int_or_0(stored_size_sum),
+			raw_size_sum=_int_or_0(raw_size_sum),
+		)
+
 	def list_chunks(self, limit: Optional[int] = None, offset: Optional[int] = None) -> List[schema.Chunk]:
 		s = select(schema.Chunk)
 		if limit is not None: