/r/friends: use friends that posted most recently

This takes advantage of the new last_submit_time and last_comment_time timestamps on the Account objects to determine which friends have posted most recently. Ideally the ability to sort on data columns would have been added into the general _query() function, but that seems to be fairly complex, so this was a lot simpler of a method for addressing this specific problem.
reddit-archive · Oct 1, 2015 · e7adea1 · e7adea1
1 parent 22f566b
commit e7adea1
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Showing 4 changed files with 61 additions and 10 deletions.
diff --git a/r2/r2/lib/db/tdb_sql.py b/r2/r2/lib/db/tdb_sql.py
@@ -928,6 +928,40 @@ def find_data(type_id, get_cols, sort, limit, offset, constraints):
     return Results(r, lambda(row): row if get_cols else row.thing_id)
 
 
+def sort_thing_ids_by_data_value(type_id, thing_ids, value_name,
+        limit=None, desc=False):
+    """Order thing_ids by the value of a data column."""
+
+    thing_table, data_table = get_thing_table(type_id)
+
+    join = thing_table.join(data_table,
+        data_table.c.thing_id == thing_table.c.thing_id)
+
+    query = (sa.select(
+            [thing_table.c.thing_id],
+            sa.and_(
+                thing_table.c.thing_id.in_(thing_ids),
+                thing_table.c.deleted == False,
+                thing_table.c.spam == False,
+                data_table.c.key == value_name,
+            )
+        )
+        .select_from(join)
+    )
+
+    sort_column = data_table.c.value
+    if desc:
+        sort_column = sa.desc(sort_column)
+    query = query.order_by(sort_column)
+
+    if limit:
+        query = query.limit(limit)
+
+    rows = query.execute()
+
+    return Results(rows, lambda(row): row.thing_id)
+
+
 def find_rels(rel_type_id, get_cols, sort, limit, offset, constraints):
     tables = get_rel_table(rel_type_id)
     r_table, t1_table, t2_table, d_table = tables

diff --git a/r2/r2/lib/db/thing.py b/r2/r2/lib/db/thing.py
@@ -652,6 +652,12 @@ def _query(cls, *all_rules, **kw):
 
         return Things(cls, *rules, **kw)
 
+    @classmethod
+    def sort_ids_by_data_value(cls, thing_ids, value_name,
+            limit=None, desc=False):
+        return tdb.sort_thing_ids_by_data_value(
+            cls._type_id, thing_ids, value_name, limit, desc)
+
     def update_search_index(self, boost_only=False):
         msg = {'fullname': self._fullname}
         if boost_only:

diff --git a/r2/r2/models/account.py b/r2/r2/models/account.py
@@ -452,13 +452,24 @@ def add_friend_note(self, friend, note):
         rel.note = note
         rel._commit()
 
-    @memoize("get_random_friends", time=30*60)
-    def get_random_friends(self, limit=100):
-        friends = self.friend_ids()
-        if len(friends) > limit:
-            friends = random.sample(friends, limit)
-
-        return friends
+    def _get_friend_ids_by(self, data_value_name, limit):
+        friend_ids = self.friend_ids()
+        if len(friend_ids) <= limit:
+            return friend_ids
+
+        with g.stats.get_timer("friends_query.%s" % data_value_name):
+            result = self.sort_ids_by_data_value(
+                friend_ids, data_value_name, limit=limit, desc=True)
+
+        return result.fetchall()
+
+    @memoize("get_recently_submitted_friend_ids", time=10*60)
+    def get_recently_submitted_friend_ids(self, limit=100):
+        return self._get_friend_ids_by("last_submit_time", limit)
+
+    @memoize("get_recently_commented_friend_ids", time=10*60)
+    def get_recently_commented_friend_ids(self, limit=100):
+        return self._get_friend_ids_by("last_comment_time", limit)
 
     def delete(self, delete_message=None):
         self.delete_message = delete_message

diff --git a/r2/r2/models/subreddit.py b/r2/r2/models/subreddit.py
@@ -1547,7 +1547,7 @@ class FriendsSR(FakeSubreddit):
     def get_links(self, sort, time):
         from r2.lib.db import queries
 
-        friends = c.user.get_random_friends()
+        friends = c.user.get_recently_submitted_friend_ids()
         if not friends:
             return []
 
@@ -1567,7 +1567,7 @@ def get_links(self, sort, time):
     def get_all_comments(self):
         from r2.lib.db import queries
 
-        friends = c.user.get_random_friends()
+        friends = c.user.get_recently_commented_friend_ids()
         if not friends:
             return []
 
@@ -1588,7 +1588,7 @@ def get_all_comments(self):
     def get_gilded(self):
         from r2.lib.db.queries import get_gilded_users
 
-        friends = c.user.get_random_friends()
+        friends = c.user.friend_ids()
 
         if not friends:
             return []