properly seed intra-sync persistent delta reader cache on new sync (#19702)

Author: altendky

chia/data_layer/data_store.py

@@ -200,7 +200,7 @@ async def insert_into_data_store_from_file(
         root_hash: Optional[bytes32],
         filename: Path,
         delta_reader: Optional[DeltaReader] = None,
-    ) -> None:
+    ) -> Optional[DeltaReader]:
         if root_hash is None:
             merkle_blob = MerkleBlob(b"")
         else:
@@ -233,6 +233,7 @@ async def insert_into_data_store_from_file(
 
         # Don't store these blob objects into cache, since their data structures are not calculated yet.
         await self.insert_root_from_merkle_blob(merkle_blob, store_id, Status.COMMITTED, update_cache=False)
+        return delta_reader
 
     async def build_merkle_blob_queries_for_missing_hashes(
         self,

chia/data_layer/download_data.py

@@ -177,7 +177,7 @@ async def insert_from_delta_file(
     if group_files_by_store:
         client_foldername.joinpath(f"{store_id}").mkdir(parents=True, exist_ok=True)
 
-    delta_reader = DeltaReader(internal_nodes={}, leaf_nodes={})
+    delta_reader: Optional[DeltaReader] = None
 
     for root_hash in root_hashes:
         timestamp = int(time.time())
@@ -218,7 +218,7 @@ async def insert_from_delta_file(
                     existing_generation,
                     group_files_by_store,
                 )
-                await data_store.insert_into_data_store_from_file(
+                delta_reader = await data_store.insert_into_data_store_from_file(
                     store_id,
                     None if root_hash == bytes32.zeros else root_hash,
                     target_filename_path,