Add db_index=True to object_pk and is_removed fields

alter object_pk field to CharField(max_length=64) for compatibility
with MySQL.

Author: atodorov

HISTORY.rst

@@ -8,6 +8,14 @@ Unreleased
 
 * Dropped support for Django 1.11, 2.0, and 2.1.
 * Added the ``delete_stale_comments`` management command.
+* Added db_index to ``object_pk`` and ``is_removed`` fields.
+* Altered ``object_pk`` from ``TextField`` to ``CharField(max_length=64)``
+  so that the field can be indexed on MySQL, too. **Warning:** if you attach
+  comments to objects whose primary key is serialized to more than 64
+  characters, you should provide a custom Comment model
+  (more about that in the documentation) with an appropriate
+  ``object_pk`` field.
+
 
 2.0.0 (2020-12-20)
 ------------------

django_comments/abstracts.py

@@ -23,7 +23,7 @@ class BaseCommentAbstractModel(models.Model):
                                      verbose_name=_('content type'),
                                      related_name="content_type_set_for_%(class)s",
                                      on_delete=models.CASCADE)
-    object_pk = models.TextField(_('object ID'))
+    object_pk = models.CharField(_('object ID'), db_index=True, max_length=64)
     content_object = GenericForeignKey(ct_field="content_type", fk_field="object_pk")
 
     # Metadata about the comment
@@ -65,7 +65,7 @@ class CommentAbstractModel(BaseCommentAbstractModel):
     is_public = models.BooleanField(_('is public'), default=True,
                                     help_text=_('Uncheck this box to make the comment effectively '
                                                 'disappear from the site.'))
-    is_removed = models.BooleanField(_('is removed'), default=False,
+    is_removed = models.BooleanField(_('is removed'), default=False, db_index=True,
                                      help_text=_('Check this box if the comment is inappropriate. '
                                                  'A "This comment has been removed" message will '
                                                  'be displayed instead.'))

django_comments/migrations/0004_add_object_pk_is_removed_index.py

@@ -0,0 +1,25 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('django_comments', '0003_add_submit_date_index'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='comment',
+            name='is_removed',
+            field=models.BooleanField(
+                db_index=True, default=False,
+                help_text='Check this box if the comment is inappropriate. '
+                          'A "This comment has been removed" message will be displayed instead.',
+                verbose_name='is removed'),
+        ),
+        migrations.AlterField(
+            model_name='comment',
+            name='object_pk',
+            field=models.CharField(max_length=64, db_index=True, verbose_name='object ID'),
+        ),
+    ]

docs/models.txt

@@ -28,8 +28,8 @@ The comment models
 
     .. attribute:: object_pk
 
-        A :class:`~django.db.models.TextField` containing the primary
-        key of the object the comment is attached to.
+        A :class:`~django.db.models.CharField` containing the primary
+        key of the object the comment is attached to. ``max_length=64``.
 
     .. attribute:: site