Minor improvements to bookwyrm_book trigger code

- do not COALESCE columns that cannot be NULL
- do not bring bookwyrm_book to author names JOIN
- add comments documenting the four steps

bookwyrm/migrations/0191_migrate_search_vec_triggers_to_pgtriggers.py

@@ -32,8 +32,8 @@ class Migration(migrations.Migration):
             trigger=pgtrigger.compiler.Trigger(
                 name="update_search_vector_on_book_edit",
                 sql=pgtrigger.compiler.UpsertTriggerSql(
-                    func="new.search_vector := coalesce(nullif(setweight(to_tsvector('english', coalesce(new.title, '')), 'A'), ''), setweight(to_tsvector('simple', coalesce(new.title, '')), 'A')) || setweight(to_tsvector('english', coalesce(new.subtitle, '')), 'B') || (SELECT setweight(to_tsvector('simple', coalesce(array_to_string(array_agg(bookwyrm_author.name), ' '), '')), 'C') FROM bookwyrm_book LEFT OUTER JOIN bookwyrm_book_authors ON bookwyrm_book.id = bookwyrm_book_authors.book_id LEFT OUTER JOIN bookwyrm_author ON bookwyrm_book_authors.author_id = bookwyrm_author.id WHERE bookwyrm_book.id = new.id ) || setweight(to_tsvector('english', coalesce(new.series, '')), 'D');RETURN NEW;",
+                    func="new.search_vector := setweight(coalesce(nullif(to_tsvector('english', new.title), ''), to_tsvector('simple', new.title)), 'A') || setweight(to_tsvector('english', coalesce(new.subtitle, '')), 'B') || (SELECT setweight(to_tsvector('simple', coalesce(array_to_string(array_agg(bookwyrm_author.name), ' '), '')), 'C') FROM bookwyrm_author LEFT JOIN bookwyrm_book_authors ON bookwyrm_author.id = bookwyrm_book_authors.author_id WHERE bookwyrm_book_authors.book_id = new.id ) || setweight(to_tsvector('english', coalesce(new.series, '')), 'D');RETURN NEW;",
-                    hash="9c898d46dfb7492ecd18f6c692bbecfa548f0e85",
+                    hash="77d6399497c0a89b0bf09d296e33c396da63705c",
                     operation='INSERT OR UPDATE OF "title", "subtitle", "series", "search_vector"',
                     pgid="pgtrigger_update_search_vector_on_book_edit_bec58",
                     table="bookwyrm_book",

bookwyrm/models/book.py

@@ -247,19 +247,20 @@ class Book(BookDataModel):
                 | pgtrigger.UpdateOf("title", "subtitle", "series", "search_vector"),
                 func=format_trigger(
                     """new.search_vector :=
-                         COALESCE(
+                         -- title, with priority A (parse in English, default to simple if empty)
-                             NULLIF(setweight(to_tsvector('english', COALESCE(new.title, '')), 'A'), ''),
+                         setweight(COALESCE(nullif(
-                             setweight(to_tsvector('simple', COALESCE(new.title, '')), 'A')
+                                       to_tsvector('english', new.title), ''),
-                         ) ||
+                                       to_tsvector('simple', new.title)), 'A') ||
+                         -- subtitle, with priority B (always in English?)
                          setweight(to_tsvector('english', COALESCE(new.subtitle, '')), 'B') ||
+                         -- list of authors, with priority C (TODO: add aliases?, bookwyrm-social#3063)
                          (SELECT setweight(to_tsvector('simple', COALESCE(array_to_string(ARRAY_AGG(bookwyrm_author.name), ' '), '')), 'C')
-                             FROM bookwyrm_book
+                           FROM bookwyrm_author
-                             LEFT OUTER JOIN bookwyrm_book_authors
+                           LEFT JOIN bookwyrm_book_authors
-                             ON bookwyrm_book.id = bookwyrm_book_authors.book_id
+                               ON bookwyrm_author.id = bookwyrm_book_authors.author_id
-                             LEFT OUTER JOIN bookwyrm_author
+                           WHERE bookwyrm_book_authors.book_id = new.id
-                             ON bookwyrm_book_authors.author_id = bookwyrm_author.id
-                             WHERE bookwyrm_book.id = new.id
                          ) ||
+                         --- last: series name, with lowest priority
                          setweight(to_tsvector('english', COALESCE(new.series, '')), 'D');
                        RETURN new;
                 """

bookwyrm/tests/test_book_search.py

@@ -178,15 +178,17 @@ class SearchVectorTest(TestCase):
         book = self._create_book("Hear We Come", "John")
         self.assertEqual(book.search_vector, "'come':3A 'hear':1A 'john':4C")
 
+    def test_search_vector_no_author(self):
+        """book with no authors gets processed normally"""
+        book = self._create_book("Book", None, series="Bunch")
+        self.assertEqual(book.search_vector, "'book':1A 'bunch':2")
+
     @staticmethod
     def _create_book(
         title, author_name, /, *, subtitle="", series="", author_alias=None
     ):
         """quickly create a book"""
         work = models.Work.objects.create(title="work")
-        author = models.Author.objects.create(
-            name=author_name, aliases=author_alias or []
-        )
         edition = models.Edition.objects.create(
             title=title,
             series=series or None,
@@ -194,6 +196,10 @@ class SearchVectorTest(TestCase):
             isbn_10="0000000000",
             parent_work=work,
         )
+        if author_name is not None:
+            author = models.Author.objects.create(
+                name=author_name, aliases=author_alias or []
+            )
             edition.authors.add(author)
             edition.save(broadcast=False)
         edition.refresh_from_db()