generate_preference_list: Use SQL to retrieve tags of elements

server/entertainment_decider/models.py

@@ -8,6 +8,7 @@ from datetime import datetime, timedelta
 from functools import cache
 import gzip
 from itertools import chain
+import itertools
 import json
 import math
 import logging
@@ -20,6 +21,7 @@ from typing import (
     Mapping,
     NewType,
     Optional,
+    Sequence,
     Set,
     Tuple,
     TypeAlias,
@@ -423,9 +425,10 @@ def generate_preference_list(
     # score calc
     now = datetime.now()
 
-    @cache
+    elem_tag_map = get_all_elements_tags_recursive()
+
     def all_tags(element: MediaElement) -> List[Tag]:
-        return [tag for tag in element.all_tags if tag.use_for_preferences]
+        return elem_tag_map.get(element.id, [])
 
     # TODO prepare static score in parallel (or cache it in DB for longer)
     @cache
@@ -1330,6 +1333,42 @@ def get_all_considered(
     )
 
 
+def get_all_elements_tags_recursive() -> Mapping[int, Sequence[Tag]]:
+    elem_tag_query: Iterable[Tuple[int, int]] = db.execute(
+        """
+        WITH RECURSIVE found_tag (mediaelement_id, tag_id) AS
+        (
+                SELECT mediaelement_tag.mediaelement, mediaelement_tag.tag
+                FROM mediaelement_tag
+            UNION
+                SELECT mediacollectionlink.element, mediacollection_tag.tag
+                FROM mediacollectionlink
+                JOIN mediacollection_tag ON mediacollectionlink.collection = mediacollection_tag.mediacollection
+            UNION
+                SELECT found_tag.mediaelement_id, tag_tag.tag_2
+                FROM found_tag
+                JOIN tag_tag ON found_tag.tag_id = tag_tag.tag
+        )
+        SELECT found_tag.mediaelement_id, found_tag.tag_id
+        FROM found_tag
+        JOIN tag ON found_tag.tag_id = tag.id
+        WHERE tag.use_for_preferences
+        ORDER BY mediaelement_id, tag_id;
+    """
+    )
+
+    @cache
+    def get_tag(tag_id: int) -> Tag:
+        return Tag[tag_id]
+
+    return {
+        elem_id: [get_tag(tag_id) for _, tag_id in group_iter]
+        for elem_id, group_iter in itertools.groupby(
+            elem_tag_query, key=lambda row: row[0]
+        )
+    }
+
+
 def update_element_lookup_cache(collection_ids: List[int] = []):
     logging.info(
         f"Rebuild {MEDIAELEMENT_BLOCKING_LOOKUP_CACHE_TABLE} for {len(collection_ids) if collection_ids else 'all'} collections …"