Permit airflow db migrate -r with an empty database

airflow-core/.pre-commit-config.yaml

@@ -194,7 +194,9 @@ repos:
         pass_filenames: true
         files: ^src/airflow/migrations/versions/.*\.py$
         exclude:
-          ^src/airflow/migrations/versions/0028_3_0_0_drop_ab_user_id_foreign_key.py$
+          (?x)
+          ^src/airflow/migrations/versions/0000_2_6_2_squashed_migrations\.py$|
+          ^src/airflow/migrations/versions/0028_3_0_0_drop_ab_user_id_foreign_key\.py$
       - id: ts-compile-lint-ui
         name: Compile / format / lint UI
         description: TS types generation / ESLint / Prettier new UI files

airflow-core/docs/img/airflow_erd.sha256

@@ -1 +1 @@
-99114dbbb7c6e7ae792b0dd380c55901aea3185c7e8f969c2e44b8fa69e2a467
+5e7215fa50868683623f2f4ff4e1ede41beeda84acb141eb3f36c854b9b24314

airflow-core/docs/migrations-ref.rst

@@ -242,7 +242,9 @@ Here's the list of all the Database Migrations that are executed via when you ru
 +-------------------------+------------------+-------------------+--------------------------------------------------------------+
 | ``788397e78828``        | ``937cbd173ca1`` | ``2.7.0``         | Add custom_operator_name column.                             |
 +-------------------------+------------------+-------------------+--------------------------------------------------------------+
-| ``937cbd173ca1`` (base) | ``None``         | ``2.7.0``         | Add index to task_instance table.                            |
+| ``937cbd173ca1``        | ``4bc4d934e2bc`` | ``2.7.0``         | Add index to task_instance table.                            |
++-------------------------+------------------+-------------------+--------------------------------------------------------------+
+| ``4bc4d934e2bc`` (base) | ``None``         | ``2.6.2``         | Create initial database state from Airflow v2.6.2.           |
 +-------------------------+------------------+-------------------+--------------------------------------------------------------+
 
  .. End of auto-generated table

airflow-core/src/airflow/migrations/versions/0001_2_7_0_add_index_to_task_instance_table.py

@@ -20,7 +20,7 @@
 Add index to task_instance table.
 
 Revision ID: 937cbd173ca1
-Revises: None
+Revises: 4bc4d934e2bc
 Create Date: 2023-05-03 11:31:32.527362
 
 """
@@ -31,7 +31,7 @@
 
 # revision identifiers, used by Alembic.
 revision = "937cbd173ca1"
-down_revision = None
+down_revision = "4bc4d934e2bc"
 branch_labels = None
 depends_on = None
 airflow_version = "2.7.0"

airflow-core/src/airflow/utils/db.py

@@ -101,6 +101,7 @@ class MappedClassProtocol(Protocol):
 log = logging.getLogger(__name__)
 
 _REVISION_HEADS_MAP: dict[str, str] = {
+    "2.6.2": "4bc4d934e2bc",
     "2.7.0": "405de8318b3a",
     "2.8.0": "10b52ebd31f7",
     "2.8.1": "88344c1d9134",
@@ -167,7 +168,7 @@ def add_default_pool_if_not_exists(session: Session = NEW_SESSION):
     """Add default pool if it does not exist."""
     from airflow.models.pool import Pool
 
-    if not Pool.get_pool(Pool.DEFAULT_POOL_NAME, session=session):
+    if not session.scalar(select(Pool.id).where(Pool.pool == Pool.DEFAULT_POOL_NAME)):
         default_pool = Pool(
             pool=Pool.DEFAULT_POOL_NAME,
             slots=conf.getint(section="core", key="default_pool_task_slot_count"),
@@ -1118,7 +1119,7 @@ def upgradedb(
     if errors_seen:
         exit(1)
 
-    if not _get_current_revision(session=session):
+    if not _get_current_revision(session=session) and not to_revision:
         # Don't load default connections
         # New DB; initialize and exit
         initdb(session=session)

scripts/in_container/run_migration_reference.py

@@ -166,7 +166,7 @@ def update_docs(revisions: Iterable[Script], app="airflow"):
 
 
 def ensure_mod_prefix(mod_name, idx, version):
-    parts = [f"{idx + 1:04}", *version]
+    parts = [f"{idx:04}", *version]
     match = re.match(r"([0-9]+)_([0-9]+)_([0-9]+)_([0-9]+)_(.+)", mod_name)
     if match:
         # previously standardized file, rebuild the name