fix: stop altering the django_comments.object_pk

As Django documentation says, handler of post_migrate must not modify
the database schema. So, leave the field data type modification to
users. Let them decide when they need to make the change.

Signed-off-by: Chenxiong Qi <qcxhome@gmail.com>

src/tcms/core/apps.py

@@ -1,117 +1,10 @@
 # -*- coding: utf-8 -*-
 
-import logging
-from datetime import datetime
-from textwrap import dedent
-
 from django.apps import AppConfig as DjangoAppConfig
-from django.conf import settings
-from django.db import connections
-from django.db.models.signals import post_migrate
 from django.utils.translation import gettext_lazy as _
 
-logger = logging.getLogger(__name__)
-
-
-SQLs = {
-    "postgresql": (
-        # Thanks for the answer: https://stackoverflow.com/q/2204058/968262
-        dedent(
-            """\
-            select 'placeholder' as ph1, 'placeholder' as ph2, i.relname as Key_name
-            from pg_class t, pg_class i, pg_index ix, pg_attribute a
-            where
-                t.oid = ix.indrelid
-                and i.oid = ix.indexrelid
-                and a.attrelid = t.oid
-                and a.attnum = ANY(ix.indkey)
-                and t.relkind = 'r'
-                and t.relname = 'django_comments'
-                and a.attname = 'object_pk'
-            order by t.relname, i.relname;
-        """
-        ),
-        "DROP INDEX {}",
-        "SELECT data_type FROM information_schema.columns "
-        "WHERE table_name = 'django_comments' AND column_name = 'object_pk'",
-        "ALTER TABLE django_comments ALTER COLUMN object_pk TYPE INTEGER "
-        "USING object_pk::integer",
-    ),
-    "mysql": (
-        # Key_name is the 3rd column
-        "SHOW INDEXES FROM django_comments WHERE Column_name = 'object_pk'",
-        "DROP INDEX {} ON django_comments",
-        "SELECT DATA_TYPE FROM information_schema.columns "
-        "WHERE table_schema = '{}' AND table_name = 'django_comments' "
-        "AND COLUMN_NAME = 'object_pk'",
-        "ALTER TABLE django_comments MODIFY object_pk INT",
-    ),
-}
-
-
-def ensure_django_comment_object_pk_is_int(*args, **kwargs):
-    for db_key, db_info in settings.DATABASES.items():
-        _, db_engine = db_info["ENGINE"].rsplit(".", 1)
-
-        if db_engine not in SQLs:
-            logger.warning(
-                "Engine %s is not supported to modify data type of column "
-                "django_comment.object_pk.",
-                db_engine,
-            )
-            return
-
-        sql_find_indexes, sql_drop_idx, query, alter = SQLs[db_engine]
-        schema_name = db_info["NAME"]
-        query = query.format(schema_name)
-
-        with connections[db_key].cursor() as cursor:
-            cursor.execute(query)
-            (type_name,) = cursor.fetchone()
-            need_modify = type_name.lower() not in ("int", "integer")
-
-        if need_modify:
-            # Before alter the column, find existing indexes and remove them.
-            # Later, the indexes will be created back.
-            # This is required since the version 2.1.0 of django-contrib-comments,
-            # which adds indexes to the django_comments.object_pk column
-
-            with connections[db_key].cursor() as cursor:
-                cursor.execute(sql_find_indexes)
-                rows = cursor.fetchall()
-
-            had_index = False
-            with connections[db_key].cursor() as cursor:
-                for row in rows:
-                    had_index = True
-                    # 2: the column name
-                    cursor.execute(sql_drop_idx.format(row[2]))
-
-            logger.info(
-                "Change django_comments.object_pk to INTEGER in database %s",
-                schema_name,
-            )
-            with connections[db_key].cursor() as cursor:
-                cursor.execute(alter)
-
-            if had_index:
-                # For this special case of django_comments, there is no special
-                # index on the original django_comments.object_pk column. So,
-                # after altering it to the integer type, a btree index is good
-                # enough. Note that, btree is the default for PostgreSQL,
-                # and the MySQL and MariaDB with InnoDB engine.
-                now = datetime.now().strftime("%Y%m%d%H%M%S")
-                with connections[db_key].cursor() as cursor:
-                    cursor.execute(
-                        f"CREATE INDEX django_comments__object_pk__{now} "
-                        f"ON django_comments (object_pk)"
-                    )
-
 
 class AppConfig(DjangoAppConfig):
     label = "tcms_core"
     name = "tcms.core"
     verbose_name = _("Core App")
-
-    def ready(self):
-        post_migrate.connect(ensure_django_comment_object_pk_is_int)