Search: Add prefix matching support

synapse/storage/search.py

@@ -140,7 +140,10 @@ def search_msgs(self, room_ids, search_term, keys):
             list of dicts
         """
         clauses = []
-        args = []
+
+        search_query = search_query = _parse_query(self.database_engine, search_term)
+
+        args = [search_query]
 
         # Make sure we don't explode because the person is in too many rooms.
         # We filter the results below regardless.
@@ -162,7 +165,7 @@ def search_msgs(self, room_ids, search_term, keys):
         if isinstance(self.database_engine, PostgresEngine):
             sql = (
                 "SELECT ts_rank_cd(vector, query) AS rank, room_id, event_id"
-                " FROM plainto_tsquery('english', ?) as query, event_search"
+                " FROM to_tsquery('english', ?) as query, event_search"
                 " WHERE vector @@ query"
             )
         elif isinstance(self.database_engine, Sqlite3Engine):
@@ -183,7 +186,7 @@ def search_msgs(self, room_ids, search_term, keys):
         sql += " ORDER BY rank DESC LIMIT 500"
 
         results = yield self._execute(
-            "search_msgs", self.cursor_to_dict, sql, *([search_term] + args)
+            "search_msgs", self.cursor_to_dict, sql, *args
         )
 
         results = filter(lambda row: row["room_id"] in room_ids, results)
@@ -197,7 +200,7 @@ def search_msgs(self, room_ids, search_term, keys):
 
         highlights = None
         if isinstance(self.database_engine, PostgresEngine):
-            highlights = yield self._find_highlights_in_postgres(search_term, events)
+            highlights = yield self._find_highlights_in_postgres(search_query, events)
 
         defer.returnValue({
             "results": [
@@ -226,7 +229,10 @@ def search_rooms(self, room_ids, search_term, keys, limit, pagination_token=None
             list of dicts
         """
         clauses = []
-        args = [search_term]
+
+        search_query = search_query = _parse_query(self.database_engine, search_term)
+
+        args = [search_query]
 
         # Make sure we don't explode because the person is in too many rooms.
         # We filter the results below regardless.
@@ -263,7 +269,7 @@ def search_rooms(self, room_ids, search_term, keys, limit, pagination_token=None
             sql = (
                 "SELECT ts_rank_cd(vector, query) as rank,"
                 " origin_server_ts, stream_ordering, room_id, event_id"
-                " FROM plainto_tsquery('english', ?) as query, event_search"
+                " FROM to_tsquery('english', ?) as query, event_search"
                 " NATURAL JOIN events"
                 " WHERE vector @@ query AND "
             )
@@ -313,7 +319,7 @@ def search_rooms(self, room_ids, search_term, keys, limit, pagination_token=None
 
         highlights = None
         if isinstance(self.database_engine, PostgresEngine):
-            highlights = yield self._find_highlights_in_postgres(search_term, events)
+            highlights = yield self._find_highlights_in_postgres(search_query, events)
 
         defer.returnValue({
             "results": [
@@ -330,15 +336,15 @@ def search_rooms(self, room_ids, search_term, keys, limit, pagination_token=None
             "highlights": highlights,
         })
 
-    def _find_highlights_in_postgres(self, search_term, events):
+    def _find_highlights_in_postgres(self, search_query, events):
         """Given a list of events and a search term, return a list of words
         that match from the content of the event.
 
         This is used to give a list of words that clients can match against to
         highlight the matching parts.
 
         Args:
-            search_term (str)
+            search_query (str)
             events (list): A list of events
 
         Returns:
@@ -370,14 +376,14 @@ def f(txn):
                 while stop_sel in value:
                     stop_sel += ">"
 
-                query = "SELECT ts_headline(?, plainto_tsquery('english', ?), %s)" % (
+                query = "SELECT ts_headline(?, to_tsquery('english', ?), %s)" % (
                     _to_postgres_options({
                         "StartSel": start_sel,
                         "StopSel": stop_sel,
                         "MaxFragments": "50",
                     })
                 )
-                txn.execute(query, (value, search_term,))
+                txn.execute(query, (value, search_query,))
                 headline, = txn.fetchall()[0]
 
                 # Now we need to pick the possible highlights out of the haedline
@@ -399,3 +405,22 @@ def _to_postgres_options(options_dict):
     return "'%s'" % (
         ",".join("%s=%s" % (k, v) for k, v in options_dict.items()),
     )
+
+
+def _parse_query(database_engine, search_term):
+    """Takes a plain unicode string from the user and converts it into a form
+    that can be passed to database.
+    We use this so that we can add prefix matching, which isn't something
+    that is supported by default.
+    """
+
+    # Pull out the individual words, discarding any non-word characters.
+    results = re.findall(r"([\w\-]+)", search_term, re.UNICODE)
+
+    if isinstance(database_engine, PostgresEngine):
+        return " & ".join(result + ":*" for result in results)
+    elif isinstance(database_engine, Sqlite3Engine):
+        return " & ".join(result + "*" for result in results)
+    else:
+        # This should be unreachable.
+        raise Exception("Unrecognized database engine")