From 724b06a77d5c2f9a28d512210235078a0c972cfa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C5=A0ar=C5=ABnas=20Nejus?= <snejus@protonmail.com>
Date: Sat, 8 Apr 2023 05:46:56 +0100
Subject: [PATCH 1/2] Define SingletonQuery to perform filtering through SQL

This slightly speeds up the queries and there's a nice side-effect where
`singleton:1` and `singleton:0` now work fine!

This is ultimately building towards replacing as many python-only
queries with SQL equivalents.
---
 beets/library.py   | 10 ++++++++++
 docs/changelog.rst |  2 ++
 test/test_query.py | 10 ++++++++++
 3 files changed, 22 insertions(+)

diff --git a/beets/library.py b/beets/library.py
index 9d5219b18..7fb96d400 100644
--- a/beets/library.py
+++ b/beets/library.py
@@ -44,6 +44,14 @@ log = logging.getLogger('beets')
 
 # Library-specific query types.
 
+class SingletonQuery(dbcore.FieldQuery):
+    def __new__(cls, field, value, *args, **kwargs):
+        query = dbcore.query.NoneQuery('album_id')
+        if util.str2bool(value):
+            return query
+        return dbcore.query.NotQuery(query)
+
+
 class PathQuery(dbcore.FieldQuery):
     """A query that matches all items under a given path.
 
@@ -569,6 +577,8 @@ class Item(LibModel):
 
     _sorts = {'artist': SmartArtistSort}
 
+    _queries = {'singleton': SingletonQuery}
+
     _format_config_key = 'format_item'
 
     # Cached album object. Read-only.
diff --git a/docs/changelog.rst b/docs/changelog.rst
index 39cd8fa2d..01f160f8e 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -11,6 +11,8 @@ for Python 3.6).
 
 New features:
 
+* :ref:`list-cmd` `singleton:true` queries have been made faster
+* :ref:`list-cmd` `singleton:1` and `singleton:0` can now alternatively be used in queries, same as `comp`
 * --from-logfile now parses log files using a UTF-8 encoding in `beets/beets/ui/commands.py`.
   :bug:`4693` 
 * Added additional error handling for `spotify` plugin.
diff --git a/test/test_query.py b/test/test_query.py
index 3d7b56781..5458676db 100644
--- a/test/test_query.py
+++ b/test/test_query.py
@@ -290,11 +290,21 @@ class GetTest(DummyDataTestCase):
         results = self.lib.items(q)
         self.assert_items_matched(results, ['beets 4 eva'])
 
+    def test_singleton_1(self):
+        q = 'singleton:1'
+        results = self.lib.items(q)
+        self.assert_items_matched(results, ['beets 4 eva'])
+
     def test_singleton_false(self):
         q = 'singleton:false'
         results = self.lib.items(q)
         self.assert_items_matched(results, ['foo bar', 'baz qux'])
 
+    def test_singleton_0(self):
+        q = 'singleton:0'
+        results = self.lib.items(q)
+        self.assert_items_matched(results, ['foo bar', 'baz qux'])
+
     def test_compilation_true(self):
         q = 'comp:true'
         results = self.lib.items(q)

From 699e12bd881c1e52d4b15b3d8e7d2f7468a5ceca Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C5=A0ar=C5=ABnas=20Nejus?= <snejus@protonmail.com>
Date: Sun, 9 Apr 2023 18:18:34 +0100
Subject: [PATCH 2/2] Add explanatory docstring

---
 beets/library.py | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/beets/library.py b/beets/library.py
index 7fb96d400..b52d5f873 100644
--- a/beets/library.py
+++ b/beets/library.py
@@ -45,6 +45,15 @@ log = logging.getLogger('beets')
 # Library-specific query types.
 
 class SingletonQuery(dbcore.FieldQuery):
+    """This query is responsible for the 'singleton' lookup.
+
+    It is based on the FieldQuery and constructs a SQL clause
+    'album_id is NULL' which yields the same result as the previous filter
+    in Python but is more performant since it's done in SQL.
+
+    Using util.str2bool ensures that lookups like singleton:true, singleton:1
+    and singleton:false, singleton:0 are handled consistently.
+    """
     def __new__(cls, field, value, *args, **kwargs):
         query = dbcore.query.NoneQuery('album_id')
         if util.str2bool(value):