API, DB: add document counting for entity overview request

Extends return value of `get_latest_snapshots` method in `Database`
and extends API to provide that information.

dp3/api/internal/entity_response_models.py

@@ -22,12 +22,15 @@ class EntityState(BaseModel):
 class EntityEidList(BaseModel):
     """List of entity eids and their data based on latest snapshot
 
-    Includes timestamp of latest snapshot creation.
+    Includes timestamp of latest snapshot creation, count of returned documents
+    and total count of documents available under specified filter.
 
     Data does not include history of observations attributes and timeseries.
     """
 
     time_created: Optional[datetime]
+    count: int
+    total_count: int
     data: list[dict]
 
 

dp3/api/routers/entity.py

@@ -42,18 +42,21 @@ async def list_entity_type_eids(
 
     If `eid_filter` is not empty, returns only `id`s containing substring `eid_filter`.
     """
-    cursor = DB.get_latest_snapshots(etype, eid_filter).skip(skip).limit(limit)
+    cursor, total_count = DB.get_latest_snapshots(etype, eid_filter)
+    cursor_page = cursor.skip(skip).limit(limit)
 
     time_created = None
 
     # Remove _id field
-    result = list(cursor)
+    result = list(cursor_page)
     for r in result:
         time_created = r["_time_created"]
         del r["_time_created"]
         del r["_id"]
 
-    return EntityEidList(time_created=time_created, data=result)
+    return EntityEidList(
+        time_created=time_created, count=len(result), total_count=total_count, data=result
+    )
 
 
 @router.get("/{etype}/{eid}")

dp3/database/database.py

@@ -329,12 +329,16 @@ def get_latest_snapshot(self, etype: str, eid: str) -> dict:
         snapshot_col = self._snapshots_col_name(etype)
         return self._db[snapshot_col].find_one({"eid": eid}, sort=[("_id", -1)]) or {}
 
-    def get_latest_snapshots(self, etype: str, eid_filter: str = "") -> pymongo.cursor.Cursor:
+    def get_latest_snapshots(
+        self, etype: str, eid_filter: str = ""
+    ) -> (pymongo.cursor.Cursor, int):
         """Get latest snapshots of given `etype`.
 
         This method is useful for displaying data on web.
 
         If `eid_filter` is not empty, returns only `eid`s containing substring `eid_filter`.
+
+        Also returns total document count (after filtering).
         """
         # Check `etype`
         self._assert_etype_exists(etype)
@@ -349,7 +353,7 @@ def get_latest_snapshots(self, etype: str, eid_filter: str = "") -> pymongo.curs
         if eid_filter != "":
             query["eid"] = {"$regex": eid_filter}
 
-        return self._db[snapshot_col].find(query)
+        return self._db[snapshot_col].find(query), self._db[snapshot_col].count_documents(query)
 
     def get_snapshots(
         self, etype: str, eid: str, t1: Optional[datetime] = None, t2: Optional[datetime] = None