Stop reading from event_refrence_hashes

Preparation for dropping this table altogether. Part of #6574.

Author: richvdh

changelog.d/11794.misc

@@ -0,0 +1 @@
+Preparation for database schema simplifications: stop reading from `event_reference_hashes`.

synapse/storage/databases/main/signatures.py

@@ -12,16 +12,19 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import Dict, Iterable, List, Tuple
+from typing import Collection, Dict, List, Tuple
 
 from unpaddedbase64 import encode_base64
 
-from synapse.storage._base import SQLBaseStore
-from synapse.storage.types import Cursor
+from synapse.crypto.event_signing import compute_event_reference_hash
+from synapse.storage.databases.main.events_worker import (
+    EventRedactBehaviour,
+    EventsWorkerStore,
+)
 from synapse.util.caches.descriptors import cached, cachedList
 
 
-class SignatureWorkerStore(SQLBaseStore):
+class SignatureWorkerStore(EventsWorkerStore):
     @cached()
     def get_event_reference_hash(self, event_id):
         # This is a dummy function to allow get_event_reference_hashes
@@ -32,7 +35,7 @@ def get_event_reference_hash(self, event_id):
         cached_method_name="get_event_reference_hash", list_name="event_ids", num_args=1
     )
     async def get_event_reference_hashes(
-        self, event_ids: Iterable[str]
+        self, event_ids: Collection[str]
     ) -> Dict[str, Dict[str, bytes]]:
         """Get all hashes for given events.
 
@@ -42,17 +45,22 @@ async def get_event_reference_hashes(
         Returns:
              A mapping of event ID to a mapping of algorithm to hash.
         """
+        events = await self.get_events(
+            event_ids,
+            redact_behaviour=EventRedactBehaviour.AS_IS,
+            allow_rejected=True,
+        )
 
-        def f(txn):
-            return {
-                event_id: self._get_event_reference_hashes_txn(txn, event_id)
-                for event_id in event_ids
-            }
+        hashes: Dict[str, Dict[str, bytes]] = {}
+        for event_id in event_ids:
+            event = events[event_id]
+            ref_alg, ref_hash_bytes = compute_event_reference_hash(event)
+            hashes[event.event_id] = {ref_alg: ref_hash_bytes}
 
-        return await self.db_pool.runInteraction("get_event_reference_hashes", f)
+        return hashes
 
     async def add_event_hashes(
-        self, event_ids: Iterable[str]
+        self, event_ids: Collection[str]
     ) -> List[Tuple[str, Dict[str, str]]]:
         """
 
@@ -70,24 +78,6 @@ async def add_event_hashes(
 
         return list(encoded_hashes.items())
 
-    def _get_event_reference_hashes_txn(
-        self, txn: Cursor, event_id: str
-    ) -> Dict[str, bytes]:
-        """Get all the hashes for a given PDU.
-        Args:
-            txn:
-            event_id: Id for the Event.
-        Returns:
-            A mapping of algorithm -> hash.
-        """
-        query = (
-            "SELECT algorithm, hash"
-            " FROM event_reference_hashes"
-            " WHERE event_id = ?"
-        )
-        txn.execute(query, (event_id,))
-        return {k: v for k, v in txn}
-
 
 class SignatureStore(SignatureWorkerStore):
     """Persistence for event signatures and hashes"""

synapse/storage/schema/__init__.py

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-SCHEMA_VERSION = 67  # remember to update the list below when updating
+SCHEMA_VERSION = 68  # remember to update the list below when updating
 """Represents the expectations made by the codebase about the database schema
 
 This should be incremented whenever the codebase changes its requirements on the
@@ -53,6 +53,9 @@
 
 Changes in SCHEMA_VERSION = 67:
     - state_events.prev_state is no longer written to.
+
+Changes in SCHEMA_VERSION = 68:
+    - event_reference_hashes is no longer read.
 """