Fix: index document versions as their root document

The search index and the LLM index hold root documents only, a root being
indexed with its newest version's content. Every write path therefore had to
remember to hand them the root. Several did not: adding or deleting a note on
a version, restoring a trashed document together with its versions, and
reprocessing a version all wrote the version into the index under its own id,
where it could be returned as a separate search result. The paths that walk the
whole library did the same: the document_index reindex command put every
version in the search index, a full LLM index rebuild embedded every version,
and an incremental LLM update scoped to a version id indexed it under its own
id. Asking for documents like a version looked the version's own id up in the
index and silently found nothing.

WriteBatch.add_or_update, WriteBatch.add_or_update_ids and
llm_index_add_or_update_document now resolve a version to its root themselves.
The reindex command and update_llm_index only walk root documents, and an
incremental LLM update is scoped to the roots of the given ids through
versioning.root_document_ids, which add_or_update_ids shares. more_like_id
returns the root's id for a version. The reprocess task no longer picks the root
for the indexes and only still clears the caches of both documents.

src/documents/management/commands/document_index.py

@@ -67,18 +67,22 @@ class Command(PaperlessCommand):
                 if options.get("recreate"):
                     wipe_index(settings.INDEX_DIR)
 
-                documents = Document.objects.select_related(
-                    "correspondent",
-                    "document_type",
-                    "storage_path",
-                    "owner",
-                ).prefetch_related(
-                    "tags",
-                    "notes__user",
-                    "custom_fields__field",
-                    "versions",
-                    "barcodes",
-                    "versions__barcodes",
+                documents = (
+                    Document.objects.filter(root_document__isnull=True)
+                    .select_related(
+                        "correspondent",
+                        "document_type",
+                        "storage_path",
+                        "owner",
+                    )
+                    .prefetch_related(
+                        "tags",
+                        "notes__user",
+                        "custom_fields__field",
+                        "versions",
+                        "barcodes",
+                        "versions__barcodes",
+                    )
                 )
                 total = documents.count()
                 rebuild_kwargs = {}

src/documents/search/_backend.py

@@ -284,9 +284,14 @@ class WriteBatch:
         and adding the new version. This ensures stale document data (e.g., after
         permission changes) doesn't persist in the index.
 
+        Only root documents are indexed, with their effective content, so a
+        version is indexed as its root document.
+
         Args:
             document: Django Document instance to index
         """
+        if document.root_document_id is not None:
+            document = document.root_document
         self.remove(document.pk)
         doc = self._backend._build_tantivy_doc(document)
         self._writer.add_document(doc)
@@ -311,20 +316,22 @@ class WriteBatch:
         An id with no matching document (e.g. deleted between the caller
         collecting ids and the batch running) is silently skipped, matching
         ``add_or_update()``'s existing single-document deferred-task behavior
-        rather than erroring or leaving a stale index entry.
+        rather than erroring or leaving a stale index entry. The id of a
+        version stands for its root document.
 
         Args:
             ids: Primary keys of Document instances to index
         """
         from documents.models import Document
         from documents.versioning import annotate_effective_content
+        from documents.versioning import root_document_ids
 
         ids = list(ids)
         if not ids:
             return
 
         queryset = annotate_effective_content(
-            Document.objects.filter(pk__in=ids)
+            Document.objects.filter(pk__in=root_document_ids(ids))
             .select_related("correspondent", "document_type", "storage_path", "owner")
             .prefetch_related(
                 "tags",

src/documents/tasks.py

@@ -490,23 +490,20 @@ def update_document_content_maybe_archive_file(
                     shutil.move(thumbnail, document.thumbnail_path)
 
             document.refresh_from_db()
-            root_document = (
-                document.root_document if document.root_document_id else document
-            )
             logger.info(
-                f"Updating index for document {root_document.pk} ({document.archive_checksum})",
+                f"Updating index for document {document_id} ({document.archive_checksum})",
             )
             from documents.search import get_backend
 
-            get_backend().add_or_update(root_document)
+            get_backend().add_or_update(document)
 
             ai_config = AIConfig()
             if ai_config.llm_index_enabled:
-                llm_index_add_or_update_document(root_document)
+                llm_index_add_or_update_document(document)
 
             clear_document_caches(document.pk)
-            if root_document.pk != document.pk:
-                clear_document_caches(root_document.pk)
+            if document.root_document_id is not None:
+                clear_document_caches(document.root_document_id)
 
         except Exception:
             logger.exception(

src/documents/tests/search/test_backend.py

@@ -293,6 +293,80 @@ class TestAddOrUpdateIds:
         assert backend.search_ids("updated", user=None) == [doc.pk]
 
 
+class TestVersionsAreIndexedAsTheirRoot:
+    """Only root documents are indexed, with their effective content, so
+    every write path that is handed a version indexes its root instead."""
+
+    @staticmethod
+    def _root_with_version() -> tuple[Document, Document]:
+        root = DocumentFactory(title="Statement", content="stale text")
+        version = DocumentFactory(
+            title="Statement",
+            content="latest text",
+            root_document=root,
+            version_index=1,
+        )
+        return root, version
+
+    def test_add_or_update_indexes_the_root_of_a_version(
+        self,
+        backend: TantivyBackend,
+    ) -> None:
+        """
+        GIVEN:
+            - A root document with a version
+        WHEN:
+            - The version is passed to add_or_update
+        THEN:
+            - The root is indexed with the version's text, and the version is not
+        """
+        root, version = self._root_with_version()
+
+        backend.add_or_update(version)
+
+        assert backend.search_ids("latest", user=None) == [root.pk]
+        assert backend.search_ids("stale", user=None) == []
+
+    def test_add_or_update_ids_indexes_each_root_once(
+        self,
+        backend: TantivyBackend,
+    ) -> None:
+        """
+        GIVEN:
+            - A root document with a version
+        WHEN:
+            - Both ids are passed to add_or_update_ids
+        THEN:
+            - The root is indexed once and the version is not indexed
+        """
+        root, version = self._root_with_version()
+
+        with backend.batch_update() as batch:
+            batch.add_or_update_ids([version.pk, root.pk])
+
+        assert backend.search_ids("Statement", user=None) == [root.pk]
+        assert backend.search_ids("latest", user=None) == [root.pk]
+
+    def test_add_or_update_ids_resolves_a_lone_version(
+        self,
+        backend: TantivyBackend,
+    ) -> None:
+        """
+        GIVEN:
+            - A root document with a version
+        WHEN:
+            - Only the version's id is passed to add_or_update_ids
+        THEN:
+            - The root is indexed
+        """
+        root, version = self._root_with_version()
+
+        with backend.batch_update() as batch:
+            batch.add_or_update_ids([version.pk])
+
+        assert backend.search_ids("latest", user=None) == [root.pk]
+
+
 class TestSearch:
     """Test search query parsing and matching via search_ids."""
 

src/documents/tests/test_api_search.py

@@ -1196,6 +1196,59 @@ class TestDocumentSearchApi(DirectoriesMixin, APITestCase):
         self.assertIn(d3.id, result_ids)
         self.assertNotIn(d4.id, result_ids)
 
+    def test_search_more_like_version_uses_its_root(self) -> None:
+        """
+        GIVEN:
+            - A document similar in content to a root document, and one that is not
+            - A version of the root document, which is never indexed
+        WHEN:
+            - API request for more like the version
+        THEN:
+            - The documents similar to the root are returned, not the version
+        """
+        indexed = {}
+        for name, title, content, day in (
+            ("root", "bank statement 1", "things i paid for in august", (2019, 3, 4)),
+            (
+                "similar",
+                "bank statement 3",
+                "things i paid for in september",
+                (2020, 7, 9),
+            ),
+            (
+                "other",
+                "Quarterly Report",
+                "quarterly revenue profit margin",
+                (2021, 11, 30),
+            ),
+        ):
+            with time_machine.travel(
+                timezone.make_aware(datetime.datetime(*day)),
+                tick=False,
+            ):
+                indexed[name] = DocumentFactory(
+                    title=title,
+                    content=content,
+                    created=datetime.date(*day),
+                    added=timezone.make_aware(datetime.datetime(*day)),
+                )
+        version = DocumentFactory(
+            root_document=indexed["root"],
+            version_index=1,
+            content="things i paid for in august",
+        )
+        backend = get_backend()
+        for document in indexed.values():
+            backend.add_or_update(document)
+
+        response = self.client.get(f"/api/documents/?more_like_id={version.id}")
+
+        self.assertEqual(response.status_code, status.HTTP_200_OK)
+        result_ids = [r["id"] for r in response.data["results"]]
+        self.assertIn(indexed["similar"].id, result_ids)
+        self.assertNotIn(indexed["other"].id, result_ids)
+        self.assertNotIn(version.id, result_ids)
+
     def test_more_like_requires_id_of_existing_document(self) -> None:
         """
         GIVEN:

src/documents/tests/test_management.py

@@ -22,6 +22,7 @@ from documents.models import Document
 from documents.tasks import update_document_content_maybe_archive_file
 from paperless_testing.assertions import FileSystemAssertsMixin
 from paperless_testing.dirs import DirectoriesMixin
+from paperless_testing.factories import DocumentFactory
 
 sample_file: Path = Path(__file__).parent / "samples" / "simple.pdf"
 
@@ -116,6 +117,27 @@ class TestMakeIndex:
         call_command("document_index", "reindex", skip_checks=True)
         mock_get_backend.return_value.rebuild.assert_called_once()
 
+    def test_reindex_skips_versions(self, mocker: MockerFixture) -> None:
+        """
+        GIVEN:
+            - A root document with a version
+        WHEN:
+            - The reindex command runs
+        THEN:
+            - Only the root document is handed to the rebuild, since a version
+              is indexed as its root
+        """
+        root = DocumentFactory()
+        DocumentFactory(root_document=root, version_index=1)
+        mock_get_backend = mocker.patch(
+            "documents.management.commands.document_index.get_backend",
+        )
+
+        call_command("document_index", "reindex", skip_checks=True)
+
+        documents = mock_get_backend.return_value.rebuild.call_args.args[0]
+        assert list(documents.values_list("pk", flat=True)) == [root.pk]
+
     def test_optimize(self) -> None:
         """Optimize command must execute without error (Tantivy handles optimization automatically)."""
         call_command("document_index", "optimize", skip_checks=True)

src/documents/tests/test_tasks.py

@@ -310,7 +310,7 @@ class TestUpdateContent(DirectoriesMixin, TestCase):
 
     @mock.patch("documents.tasks.clear_document_caches")
     @mock.patch("documents.search.get_backend")
-    def test_update_content_version_indexes_root(
+    def test_update_content_version_clears_caches_for_root(
         self,
         mock_get_backend: mock.Mock,
         mock_clear_caches: mock.Mock,
@@ -321,8 +321,8 @@ class TestUpdateContent(DirectoriesMixin, TestCase):
         WHEN:
             - Update content task is called for the version
         THEN:
-            - The version's content is updated
-            - The root document is indexed rather than the version
+            - The version's content is updated, not the root's
+            - The document is indexed
             - Caches are cleared for both
         """
         root, version = self._create_root_with_version()
@@ -334,8 +334,7 @@ class TestUpdateContent(DirectoriesMixin, TestCase):
             "my document",
         )
         self.assertEqual(Document.objects.get(pk=root.pk).content, "root content")
-        indexed = mock_get_backend.return_value.add_or_update.call_args.args[0]
-        self.assertEqual(indexed.pk, root.pk)
+        mock_get_backend.return_value.add_or_update.assert_called_once()
         mock_clear_caches.assert_has_calls(
             [mock.call(version.pk), mock.call(root.pk)],
         )
@@ -343,7 +342,7 @@ class TestUpdateContent(DirectoriesMixin, TestCase):
     @override_settings(AI_ENABLED=True, LLM_EMBEDDING_BACKEND="huggingface")
     @mock.patch("documents.tasks.llm_index_add_or_update_document")
     @mock.patch("documents.search.get_backend")
-    def test_update_content_version_updates_llm_index_for_root(
+    def test_update_content_version_updates_llm_index(
         self,
         mock_get_backend: mock.Mock,
         mock_llm_index: mock.Mock,
@@ -355,14 +354,13 @@ class TestUpdateContent(DirectoriesMixin, TestCase):
         WHEN:
             - Update content task is called for the version
         THEN:
-            - The LLM index is updated for the root document, not the version
+            - The LLM index is updated
         """
-        root, version = self._create_root_with_version()
+        _, version = self._create_root_with_version()
 
         tasks.update_document_content_maybe_archive_file(version.pk)
 
         mock_llm_index.assert_called_once()
-        self.assertEqual(mock_llm_index.call_args.args[0].pk, root.pk)
 
 
 class TestUpdateContentRemoteOCR(DirectoriesMixin, TestCase):

src/documents/versioning.py

@@ -17,9 +17,26 @@ from django.db.models.functions import RowNumber
 from documents.models import Document
 
 if TYPE_CHECKING:
+    from collections.abc import Iterable
+
     from rest_framework.request import Request
 
 
+def root_document_ids(ids: Iterable[int]) -> QuerySet[int]:
+    """
+    The ids of the root documents of the given documents: a root stands for
+    itself and a version for its root. Only the indexes' bookkeeping needs
+    this, since they hold root documents only.
+    """
+    return (
+        Document.objects.filter(pk__in=ids)
+        .annotate(root_id=Coalesce("root_document_id", "id"))
+        .order_by()
+        .values_list("root_id", flat=True)
+        .distinct()
+    )
+
+
 def versions_newest_first(documents: QuerySet[Document]) -> QuerySet[Document]:
     """
     Sorts versions so the newest one comes first using version_index and not on id,

src/documents/views.py

@@ -329,9 +329,10 @@ def _get_tantivy_query_and_mode(params):
 def _get_more_like_id(query_params: dict[str, Any], user: User | None) -> int:
     try:
         more_like_doc_id = int(query_params["more_like_id"])
-        more_like_doc = Document.objects.select_related("owner").get(
-            pk=more_like_doc_id,
-        )
+        more_like_doc = Document.objects.select_related(
+            "owner",
+            "root_document__owner",
+        ).get(pk=more_like_doc_id)
     except (TypeError, ValueError, Document.DoesNotExist):
         raise PermissionDenied(_("Invalid more_like_id"))
 
@@ -342,7 +343,8 @@ def _get_more_like_id(query_params: dict[str, Any], user: User | None) -> int:
     ):
         raise PermissionDenied(_("Insufficient permissions."))
 
-    return more_like_doc_id
+    # Only root documents are indexed, a version stands for its root
+    return more_like_doc.root_document_id or more_like_doc.pk
 
 
 class SearchParams(NamedTuple):

src/paperless_ai/indexing.py

@@ -17,6 +17,7 @@ from documents.models import PaperlessTask
 from documents.utils import IterWrapper
 from documents.utils import QuerySetStream
 from documents.utils import identity
+from documents.versioning import root_document_ids
 from paperless.config import AIConfig
 from paperless_ai.db import db_connection_released
 from paperless_ai.embedding import build_llm_index_text
@@ -443,11 +444,11 @@ def update_llm_index(
                 "Skipping LLM index update: migration check deferred; "
                 "will retry next run."
             )
-    documents = Document.objects.select_related(
-        "correspondent",
-        "document_type",
-        "storage_path",
-    ).prefetch_related("tags", "notes", "custom_fields__field")
+    documents = (
+        Document.objects.filter(root_document__isnull=True)
+        .select_related("correspondent", "document_type", "storage_path")
+        .prefetch_related("tags", "notes", "custom_fields__field")
+    )
     no_documents = not documents.exists()
 
     # Fast exit before touching config: nothing to index and no existing index.
@@ -483,7 +484,7 @@ def update_llm_index(
             msg = "LLM index rebuilt successfully."
         else:
             scoped_documents = (
-                documents.filter(id__in=document_ids)
+                documents.filter(id__in=root_document_ids(document_ids))
                 if document_ids is not None
                 else documents
             )
@@ -510,7 +511,12 @@ def update_llm_index(
 
 
 def llm_index_add_or_update_document(document: Document):
-    """Add or atomically replace a document's chunks in the index."""
+    """
+    Add or atomically replace a document's chunks in the index. Only root
+    documents are indexed, so a version is indexed as its root document.
+    """
+    if document.root_document_id is not None:
+        document = document.root_document
     config = AIConfig()
     new_nodes = build_document_node(
         document,

src/paperless_ai/tests/test_ai_indexing.py

@@ -388,6 +388,83 @@ def test_update_llm_index_partial_update(
     assert after[str(doc2.pk)] == before[str(doc2.pk)]
 
 
+@pytest.mark.django_db
+class TestLlmIndexVersions:
+    """The LLM index holds root documents only: a version is indexed as its root."""
+
+    def test_add_or_update_document_indexes_a_version_as_its_root(
+        self,
+        temp_llm_index_dir: Path,
+        mock_embed_model: FakeEmbedding,
+    ) -> None:
+        """
+        GIVEN:
+            - A root document with a version
+        WHEN:
+            - The version is passed to llm_index_add_or_update_document
+        THEN:
+            - Only the root document is in the index
+        """
+        root = DocumentFactory(content="root content")
+        version = DocumentFactory(root_document=root, version_index=1)
+
+        indexing.llm_index_add_or_update_document(version)
+
+        with indexing.get_vector_store() as store:
+            indexed = store.get_modified_times()
+
+        assert set(indexed) == {str(root.pk)}
+
+    def test_rebuild_skips_versions(
+        self,
+        temp_llm_index_dir: Path,
+        mock_embed_model: FakeEmbedding,
+    ) -> None:
+        """
+        GIVEN:
+            - A root document with a version
+        WHEN:
+            - The LLM index is rebuilt
+        THEN:
+            - Only the root document is in the index
+        """
+        root = DocumentFactory()
+        DocumentFactory(root_document=root, version_index=1)
+
+        indexing.update_llm_index(rebuild=True)
+
+        with indexing.get_vector_store() as store:
+            indexed = store.get_modified_times()
+
+        assert set(indexed) == {str(root.pk)}
+
+    def test_incremental_update_by_version_id_refreshes_the_root(
+        self,
+        temp_llm_index_dir: Path,
+        mock_embed_model: FakeEmbedding,
+    ) -> None:
+        """
+        GIVEN:
+            - An indexed root document with a version whose root was modified since
+        WHEN:
+            - An incremental update is scoped to the version's id
+        THEN:
+            - The root's entry is refreshed and no entry exists for the version
+        """
+        root = DocumentFactory()
+        version = DocumentFactory(root_document=root, version_index=1)
+        indexing.update_llm_index(rebuild=True)
+        Document.objects.filter(pk=root.pk).update(modified=timezone.now())
+        root.refresh_from_db()
+
+        indexing.update_llm_index(document_ids=[version.pk])
+
+        with indexing.get_vector_store() as store:
+            indexed = store.get_modified_times()
+
+        assert indexed == {str(root.pk): root.modified.isoformat()}
+
+
 @pytest.mark.django_db
 def test_add_or_update_document_updates_existing_entry(
     temp_llm_index_dir: Path,
@@ -637,6 +714,7 @@ class TestLlmIndexAddOrUpdateDocumentEmptyContent:
 
         doc = MagicMock(spec=Document)
         doc.id = 42
+        doc.root_document_id = None
         # Must not raise
         indexing.llm_index_add_or_update_document(doc)