From 19bc9768f109a7110c94d7ff8c928b1a22e4f51c Mon Sep 17 00:00:00 2001
From: Damien Elmes <git@ichi2.net>
Date: Sat, 9 May 2009 03:26:34 +0900
Subject: [PATCH] delete unused tags on card delete, do it efficiently

---
 anki/deck.py | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/anki/deck.py b/anki/deck.py
index ed756367c..b61fb6b1d 100644
--- a/anki/deck.py
+++ b/anki/deck.py
@@ -1122,6 +1122,21 @@ where facts.id not in (select distinct factId from cards)""")
         # note deleted
         data = [{'id': id, 'time': now} for id in ids]
         self.s.statements("insert into cardsDeleted values (:id, :time)", data)
+        # gather affected tags
+        tags = self.s.column0(
+            "select tagId from cardTags where cardId in %s" %
+            strids)
+        # delete
+        self.s.statement("delete from cardTags where cardId in %s" % strids)
+        # find out if they're used by anything else
+        unused = []
+        for tag in tags:
+            if not self.s.scalar(
+                "select 1 from cardTags where tagId = :d limit 1", d=tag):
+                unused.append(tag)
+        # delete unused
+        self.s.statement("delete from tags where id in %s and priority = 2" %
+                         ids2str(unused))
         # remove any dangling facts
         self.deleteDanglingFacts()
         self.rebuildCounts()