Remove the unused and unstable `/aggregations` endpoint. (#12293)

This endpoint was removed from MSC2675 before it was approved.
It is currently unspecified (even in any MSCs) and therefore subject to
removal. It is not implemented by any known clients.

This also changes the bundled aggregation format for `m.annotation`,
which previously included pagination tokens for the `/aggregations`
endpoint, which are no longer useful.

4 files changed, 16 insertions, 271 deletions

diff --git a/synapse/handlers/relations.py b/synapse/handlers/relations.py
index 73217d135d..b9497ff3f3 100644
--- a/synapse/handlers/relations.py
+++ b/synapse/handlers/relations.py
@@ -193,10 +193,8 @@ class RelationsHandler:
         annotations = await self._main_store.get_aggregation_groups_for_event(
             event_id, room_id
         )
-        if annotations.chunk:
-            aggregations.annotations = await annotations.to_dict(
-                cast("DataStore", self)
-            )
+        if annotations:
+            aggregations.annotations = {"chunk": annotations}
 
         references = await self._main_store.get_relations_for_event(
             event_id, event, room_id, RelationTypes.REFERENCE, direction="f"
diff --git a/synapse/rest/client/relations.py b/synapse/rest/client/relations.py
index c16078b187..55c96a2af3 100644
--- a/synapse/rest/client/relations.py
+++ b/synapse/rest/client/relations.py
@@ -12,22 +12,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-"""This class implements the proposed relation APIs from MSC 1849.
-
-Since the MSC has not been approved all APIs here are unstable and may change at
-any time to reflect changes in the MSC.
-"""
-
 import logging
 from typing import TYPE_CHECKING, Optional, Tuple
 
-from synapse.api.constants import RelationTypes
-from synapse.api.errors import SynapseError
 from synapse.http.server import HttpServer
 from synapse.http.servlet import RestServlet, parse_integer, parse_string
 from synapse.http.site import SynapseRequest
 from synapse.rest.client._base import client_patterns
-from synapse.storage.relations import AggregationPaginationToken
 from synapse.types import JsonDict, StreamToken
 
 if TYPE_CHECKING:
@@ -93,166 +84,5 @@ class RelationPaginationServlet(RestServlet):
         return 200, result
 
 
-class RelationAggregationPaginationServlet(RestServlet):
-    """API to paginate aggregation groups of relations, e.g. paginate the
-    types and counts of the reactions on the events.
-
-    Example request and response:
-
-        GET /rooms/{room_id}/aggregations/{parent_id}
-
-        {
-            chunk: [
-                {
-                    "type": "m.reaction",
-                    "key": "👍",
-                    "count": 3
-                }
-            ]
-        }
-    """
-
-    PATTERNS = client_patterns(
-        "/rooms/(?P<room_id>[^/]*)/aggregations/(?P<parent_id>[^/]*)"
-        "(/(?P<relation_type>[^/]*)(/(?P<event_type>[^/]*))?)?$",
-        releases=(),
-    )
-
-    def __init__(self, hs: "HomeServer"):
-        super().__init__()
-        self.auth = hs.get_auth()
-        self.store = hs.get_datastores().main
-        self.event_handler = hs.get_event_handler()
-
-    async def on_GET(
-        self,
-        request: SynapseRequest,
-        room_id: str,
-        parent_id: str,
-        relation_type: Optional[str] = None,
-        event_type: Optional[str] = None,
-    ) -> Tuple[int, JsonDict]:
-        requester = await self.auth.get_user_by_req(request, allow_guest=True)
-
-        await self.auth.check_user_in_room_or_world_readable(
-            room_id,
-            requester.user.to_string(),
-            allow_departed_users=True,
-        )
-
-        # This checks that a) the event exists and b) the user is allowed to
-        # view it.
-        event = await self.event_handler.get_event(requester.user, room_id, parent_id)
-        if event is None:
-            raise SynapseError(404, "Unknown parent event.")
-
-        if relation_type not in (RelationTypes.ANNOTATION, None):
-            raise SynapseError(
-                400, f"Relation type must be '{RelationTypes.ANNOTATION}'"
-            )
-
-        limit = parse_integer(request, "limit", default=5)
-        from_token_str = parse_string(request, "from")
-        to_token_str = parse_string(request, "to")
-
-        # Return the relations
-        from_token = None
-        if from_token_str:
-            from_token = AggregationPaginationToken.from_string(from_token_str)
-
-        to_token = None
-        if to_token_str:
-            to_token = AggregationPaginationToken.from_string(to_token_str)
-
-        pagination_chunk = await self.store.get_aggregation_groups_for_event(
-            event_id=parent_id,
-            room_id=room_id,
-            event_type=event_type,
-            limit=limit,
-            from_token=from_token,
-            to_token=to_token,
-        )
-
-        return 200, await pagination_chunk.to_dict(self.store)
-
-
-class RelationAggregationGroupPaginationServlet(RestServlet):
-    """API to paginate within an aggregation group of relations, e.g. paginate
-    all the 👍 reactions on an event.
-
-    Example request and response:
-
-        GET /rooms/{room_id}/aggregations/{parent_id}/m.annotation/m.reaction/👍
-
-        {
-            chunk: [
-                {
-                    "type": "m.reaction",
-                    "content": {
-                        "m.relates_to": {
-                            "rel_type": "m.annotation",
-                            "key": "👍"
-                        }
-                    }
-                },
-                ...
-            ]
-        }
-    """
-
-    PATTERNS = client_patterns(
-        "/rooms/(?P<room_id>[^/]*)/aggregations/(?P<parent_id>[^/]*)"
-        "/(?P<relation_type>[^/]*)/(?P<event_type>[^/]*)/(?P<key>[^/]*)$",
-        releases=(),
-    )
-
-    def __init__(self, hs: "HomeServer"):
-        super().__init__()
-        self.auth = hs.get_auth()
-        self.store = hs.get_datastores().main
-        self._relations_handler = hs.get_relations_handler()
-
-    async def on_GET(
-        self,
-        request: SynapseRequest,
-        room_id: str,
-        parent_id: str,
-        relation_type: str,
-        event_type: str,
-        key: str,
-    ) -> Tuple[int, JsonDict]:
-        requester = await self.auth.get_user_by_req(request, allow_guest=True)
-
-        if relation_type != RelationTypes.ANNOTATION:
-            raise SynapseError(400, "Relation type must be 'annotation'")
-
-        limit = parse_integer(request, "limit", default=5)
-        from_token_str = parse_string(request, "from")
-        to_token_str = parse_string(request, "to")
-
-        from_token = None
-        if from_token_str:
-            from_token = await StreamToken.from_string(self.store, from_token_str)
-        to_token = None
-        if to_token_str:
-            to_token = await StreamToken.from_string(self.store, to_token_str)
-
-        result = await self._relations_handler.get_relations(
-            requester=requester,
-            event_id=parent_id,
-            room_id=room_id,
-            relation_type=relation_type,
-            event_type=event_type,
-            aggregation_key=key,
-            limit=limit,
-            from_token=from_token,
-            to_token=to_token,
-        )
-
-        return 200, result
-
-
 def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     RelationPaginationServlet(hs).register(http_server)
-    RelationAggregationPaginationServlet(hs).register(http_server)
-    RelationAggregationGroupPaginationServlet(hs).register(http_server)
diff --git a/synapse/storage/databases/main/relations.py b/synapse/storage/databases/main/relations.py
index b2295fd51f..3285450742 100644
--- a/synapse/storage/databases/main/relations.py
+++ b/synapse/storage/databases/main/relations.py
@@ -26,8 +26,6 @@ from typing import (
     cast,
 )
 
-import attr
-
 from synapse.api.constants import RelationTypes
 from synapse.events import EventBase
 from synapse.storage._base import SQLBaseStore
@@ -39,8 +37,8 @@ from synapse.storage.database import (
 )
 from synapse.storage.databases.main.stream import generate_pagination_where_clause
 from synapse.storage.engines import PostgresEngine
-from synapse.storage.relations import AggregationPaginationToken, PaginationChunk
-from synapse.types import RoomStreamToken, StreamToken
+from synapse.storage.relations import PaginationChunk
+from synapse.types import JsonDict, RoomStreamToken, StreamToken
 from synapse.util.caches.descriptors import cached, cachedList
 
 if TYPE_CHECKING:
@@ -252,15 +250,8 @@ class RelationsWorkerStore(SQLBaseStore):
 
     @cached(tree=True)
     async def get_aggregation_groups_for_event(
-        self,
-        event_id: str,
-        room_id: str,
-        event_type: Optional[str] = None,
-        limit: int = 5,
-        direction: str = "b",
-        from_token: Optional[AggregationPaginationToken] = None,
-        to_token: Optional[AggregationPaginationToken] = None,
-    ) -> PaginationChunk:
+        self, event_id: str, room_id: str, limit: int = 5
+    ) -> List[JsonDict]:
         """Get a list of annotations on the event, grouped by event type and
         aggregation key, sorted by count.
 
@@ -270,79 +261,36 @@ class RelationsWorkerStore(SQLBaseStore):
         Args:
             event_id: Fetch events that relate to this event ID.
             room_id: The room the event belongs to.
-            event_type: Only fetch events with this event type, if given.
             limit: Only fetch the `limit` groups.
-            direction: Whether to fetch the highest count first (`"b"`) or
-                the lowest count first (`"f"`).
-            from_token: Fetch rows from the given token, or from the start if None.
-            to_token: Fetch rows up to the given token, or up to the end if None.
 
         Returns:
             List of groups of annotations that match. Each row is a dict with
             `type`, `key` and `count` fields.
         """
 
-        where_clause = ["relates_to_id = ?", "room_id = ?", "relation_type = ?"]
-        where_args: List[Union[str, int]] = [
+        where_args = [
             event_id,
             room_id,
             RelationTypes.ANNOTATION,
+            limit,
         ]
 
-        if event_type:
-            where_clause.append("type = ?")
-            where_args.append(event_type)
-
-        having_clause = generate_pagination_where_clause(
-            direction=direction,
-            column_names=("COUNT(*)", "MAX(stream_ordering)"),
-            from_token=attr.astuple(from_token) if from_token else None,  # type: ignore[arg-type]
-            to_token=attr.astuple(to_token) if to_token else None,  # type: ignore[arg-type]
-            engine=self.database_engine,
-        )
-
-        if direction == "b":
-            order = "DESC"
-        else:
-            order = "ASC"
-
-        if having_clause:
-            having_clause = "HAVING " + having_clause
-        else:
-            having_clause = ""
-
         sql = """
-            SELECT type, aggregation_key, COUNT(DISTINCT sender), MAX(stream_ordering)
+            SELECT type, aggregation_key, COUNT(DISTINCT sender)
             FROM event_relations
             INNER JOIN events USING (event_id)
-            WHERE {where_clause}
+            WHERE relates_to_id = ? AND room_id = ? AND relation_type = ?
             GROUP BY relation_type, type, aggregation_key
-            {having_clause}
-            ORDER BY COUNT(*) {order}, MAX(stream_ordering) {order}
+            ORDER BY COUNT(*) DESC
             LIMIT ?
-        """.format(
-            where_clause=" AND ".join(where_clause),
-            order=order,
-            having_clause=having_clause,
-        )
+        """
 
         def _get_aggregation_groups_for_event_txn(
             txn: LoggingTransaction,
-        ) -> PaginationChunk:
-            txn.execute(sql, where_args + [limit + 1])
-
-            next_batch = None
-            events = []
-            for row in txn:
-                events.append({"type": row[0], "key": row[1], "count": row[2]})
-                next_batch = AggregationPaginationToken(row[2], row[3])
-
-            if len(events) <= limit:
-                next_batch = None
+        ) -> List[JsonDict]:
+            txn.execute(sql, where_args)
 
-            return PaginationChunk(
-                chunk=list(events[:limit]), next_batch=next_batch, prev_batch=from_token
-            )
+            return [{"type": row[0], "key": row[1], "count": row[2]} for row in txn]
 
         return await self.db_pool.runInteraction(
             "get_aggregation_groups_for_event", _get_aggregation_groups_for_event_txn
diff --git a/synapse/storage/relations.py b/synapse/storage/relations.py
index fba270150b..b9d2b46799 100644
--- a/synapse/storage/relations.py
+++ b/synapse/storage/relations.py
@@ -13,11 +13,10 @@
 # limitations under the License.
 
 import logging
-from typing import TYPE_CHECKING, Any, Dict, List, Optional, Tuple
+from typing import TYPE_CHECKING, Any, Dict, List, Optional
 
 import attr
 
-from synapse.api.errors import SynapseError
 from synapse.types import JsonDict
 
 if TYPE_CHECKING:
@@ -52,33 +51,3 @@ class PaginationChunk:
             d["prev_batch"] = await self.prev_batch.to_string(store)
 
         return d
-
-
-@attr.s(frozen=True, slots=True, auto_attribs=True)
-class AggregationPaginationToken:
-    """Pagination token for relation aggregation pagination API.
-
-    As the results are order by count and then MAX(stream_ordering) of the
-    aggregation groups, we can just use them as our pagination token.
-
-    Attributes:
-        count: The count of relations in the boundary group.
-        stream: The MAX stream ordering in the boundary group.
-    """
-
-    count: int
-    stream: int
-
-    @staticmethod
-    def from_string(string: str) -> "AggregationPaginationToken":
-        try:
-            c, s = string.split("-")
-            return AggregationPaginationToken(int(c), int(s))
-        except ValueError:
-            raise SynapseError(400, "Invalid aggregation pagination token")
-
-    async def to_string(self, store: "DataStore") -> str:
-        return "%d-%d" % (self.count, self.stream)
-
-    def as_tuple(self) -> Tuple[Any, ...]:
-        return attr.astuple(self)