Add combined index for Postgres search backend. (#6548)

Fixes #6546

CHANGELOG.txt

@@ -12,6 +12,7 @@ Changelog
  * Added string representation to image Format class (Andreas Nüßlein)
  * Support returning None from `register_page_action_menu_item` and `register_snippet_action_menu_item` to skip registering an item (Vadim Karpenko)
  * Fields on a custom image model can now be defined as required / `blank=False` (Matt Westcott)
+ * Add combined index for Postgres search backend (Will Giddens)
  * Fix: Stop menu icon overlapping the breadcrumb on small viewport widths in page editor (Karran Besen)
  * Fix: Make sure document chooser pagination preserves the selected collection when moving between pages (Alex Sa)
  * Fix: Gracefully handle oEmbed endpoints returning non-JSON responses (Matt Westcott)

docs/releases/2.12.rst

@@ -35,6 +35,7 @@ Other features
  * Added string representation to image Format class (Andreas Nüßlein)
  * Support returning None from ``register_page_action_menu_item`` and ``register_snippet_action_menu_item`` to skip registering an item (Vadim Karpenko)
  * Fields on a custom image model can now be defined as required / ``blank=False`` (Matt Westcott)
+ * Add combined index for Postgres search backend (Will Giddens)
 
 
 Bug fixes

wagtail/contrib/postgres_search/migrations/0004_concat_index.py

@@ -0,0 +1,22 @@
+# Generated by Django 3.1.3 on 2020-11-13 16:55
+
+from django.db import migrations
+
+from wagtail.contrib.postgres_search.models import IndexEntry
+
+table = IndexEntry._meta.db_table
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('postgres_search', '0003_title'),
+    ]
+
+    operations = [
+        migrations.RunSQL(
+            'CREATE INDEX {0}_title_body_concat_search ON {0} '
+            'USING GIN(( title || body));'.format(table),
+            'DROP INDEX IF EXISTS {0}_title_body_concat_search;'.format(table),
+        ),
+    ]

wagtail/contrib/postgres_search/models.py

@@ -60,6 +60,8 @@ class IndexEntry(models.Model):
         unique_together = ('content_type', 'object_id')
         verbose_name = _('index entry')
         verbose_name_plural = _('index entries')
+        # An additional computed GIN index on 'title || body' is created in a SQL migration
+        # covers the default case of PostgresSearchQueryCompiler.get_index_vectors.
         indexes = [GinIndex(fields=['autocomplete']),
                    GinIndex(fields=['title']),
                    GinIndex(fields=['body'])]