Define datetime and StringID column types centrally in migrations

We have various flavours of the code all over the place in many
migration files -- which leads to duplication and things not being in
sync.

This pulls them once in to a central location.

airflow/migrations/db_types.py

@@ -0,0 +1,86 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+#
+import sys
+
+import sqlalchemy as sa
+from alembic import context
+from lazy_object_proxy import Proxy
+
+######################################
+# Note about this module:
+#
+# It loads the specific type dynamically at runtime. For IDE/typing support
+# there is an associated db_types.pyi. If you add a new type in here, add a
+# simple version in there too.
+######################################
+
+
+def _mssql_use_date_time2():
+    conn = context.get_bind()
+    result = conn.execute(
+        """SELECT CASE WHEN CONVERT(VARCHAR(128), SERVERPROPERTY ('productversion'))
+        like '8%' THEN '2000' WHEN CONVERT(VARCHAR(128), SERVERPROPERTY ('productversion'))
+        like '9%' THEN '2005' ELSE '2005Plus' END AS MajorVersion"""
+    ).fetchone()
+    mssql_version = result[0]
+    return mssql_version not in ("2000", "2005")
+
+
+MSSQL_USE_DATE_TIME2 = Proxy(_mssql_use_date_time2)
+
+
+def _mssql_TIMESTAMP():
+    from sqlalchemy.dialects import mssql
+
+    return mssql.DATETIME2(precision=6) if MSSQL_USE_DATE_TIME2 else mssql.DATETIME
+
+
+def _mysql_TIMESTAMP():
+    from sqlalchemy.dialects import mysql
+
+    return mysql.TIMESTAMP(fsp=6, timezone=True)
+
+
+def _sa_TIMESTAMP():
+    return sa.TIMESTAMP(timezone=True)
+
+
+def _sa_StringID():
+    from airflow.models.base import StringID
+
+    return StringID
+
+
+def __getattr__(name):
+    if name in ["TIMESTAMP", "StringID"]:
+        dialect = context.get_bind().dialect.name
+        module = globals()
+
+        # Lookup the type based on the dialect specific type, or fallback to the generic type
+        type_ = module.get(f'_{dialect}_{name}', None) or module.get(f'_sa_{name}')
+        val = module[name] = type_()
+        return val
+
+    raise AttributeError(f"module {__name__} has no attribute {name}")
+
+
+if sys.version_info < (3, 7):
+    from pep562 import Pep562
+
+    Pep562(__name__)

airflow/migrations/db_types.pyi

@@ -0,0 +1,28 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+#
+
+import sqlalchemy as sa
+
+TIMESTAMP = sa.TIMESTAMP
+"""Database specific timestamp with timezone"""
+
+StringID = sa.String
+"""String column type with correct DB collation applied"""
+
+MSSQL_USE_DATE_TIME2: bool

airflow/migrations/versions/03afc6b6f902_increase_length_of_fab_ab_view_menu_.py

@@ -28,7 +28,7 @@
 from alembic import op
 from sqlalchemy.engine.reflection import Inspector
 
-from airflow.models.base import COLLATION_ARGS
+from airflow.migrations.db_types import StringID
 
 # revision identifiers, used by Alembic.
 revision = '03afc6b6f902'
@@ -63,7 +63,7 @@ def upgrade():
             op.alter_column(
                 table_name='ab_view_menu',
                 column_name='name',
-                type_=sa.String(length=250, **COLLATION_ARGS),
+                type_=StringID(length=250),
                 nullable=False,
             )
 

airflow/migrations/versions/0a2a5b66e19d_add_task_reschedule_table.py

@@ -24,9 +24,8 @@
 """
 import sqlalchemy as sa
 from alembic import op
-from sqlalchemy.dialects import mysql
 
-from airflow.models.base import COLLATION_ARGS
+from airflow.migrations.db_types import TIMESTAMP, StringID
 
 # revision identifiers, used by Alembic.
 revision = '0a2a5b66e19d'
@@ -38,43 +37,25 @@
 INDEX_NAME = 'idx_' + TABLE_NAME + '_dag_task_date'
 
 
-# For Microsoft SQL Server, TIMESTAMP is a row-id type,
-# having nothing to do with date-time.  DateTime() will
-# be sufficient.
-def mssql_timestamp():
-    return sa.DateTime()
-
-
-def mysql_timestamp():
-    return mysql.TIMESTAMP(fsp=6)
-
-
-def sa_timestamp():
-    return sa.TIMESTAMP(timezone=True)
-
-
 def upgrade():
     # See 0e2a74e0fc9f_add_time_zone_awareness
-    conn = op.get_bind()
-    if conn.dialect.name == 'mysql':
-        timestamp = mysql_timestamp
-    elif conn.dialect.name == 'mssql':
-        timestamp = mssql_timestamp
-    else:
-        timestamp = sa_timestamp
+    timestamp = TIMESTAMP
+    if op.get_bind().dialect.name == 'mssql':
+        # We need to keep this as it was for this old migration on mssql
+        timestamp = sa.DateTime()
 
     op.create_table(
         TABLE_NAME,
         sa.Column('id', sa.Integer(), nullable=False),
-        sa.Column('task_id', sa.String(length=250, **COLLATION_ARGS), nullable=False),
-        sa.Column('dag_id', sa.String(length=250, **COLLATION_ARGS), nullable=False),
+        sa.Column('task_id', StringID(), nullable=False),
+        sa.Column('dag_id', StringID(), nullable=False),
         # use explicit server_default=None otherwise mysql implies defaults for first timestamp column
-        sa.Column('execution_date', timestamp(), nullable=False, server_default=None),
+        sa.Column('execution_date', timestamp, nullable=False, server_default=None),
         sa.Column('try_number', sa.Integer(), nullable=False),
-        sa.Column('start_date', timestamp(), nullable=False),
-        sa.Column('end_date', timestamp(), nullable=False),
+        sa.Column('start_date', timestamp, nullable=False),
+        sa.Column('end_date', timestamp, nullable=False),
         sa.Column('duration', sa.Integer(), nullable=False),
-        sa.Column('reschedule_date', timestamp(), nullable=False),
+        sa.Column('reschedule_date', timestamp, nullable=False),
         sa.PrimaryKeyConstraint('id'),
         sa.ForeignKeyConstraint(
             ['task_id', 'dag_id', 'execution_date'],

airflow/migrations/versions/142555e44c17_add_data_interval_start_end_to_dagmodel_and_dagrun.py

@@ -25,8 +25,9 @@
 """
 
 from alembic import op
-from sqlalchemy import TIMESTAMP, Column
-from sqlalchemy.dialects import mssql, mysql
+from sqlalchemy import Column
+
+from airflow.migrations.db_types import TIMESTAMP
 
 # Revision identifiers, used by Alembic.
 revision = "142555e44c17"
@@ -35,36 +36,14 @@
 depends_on = None
 
 
-def _use_date_time2(conn):
-    result = conn.execute(
-        """SELECT CASE WHEN CONVERT(VARCHAR(128), SERVERPROPERTY ('productversion'))
-        like '8%' THEN '2000' WHEN CONVERT(VARCHAR(128), SERVERPROPERTY ('productversion'))
-        like '9%' THEN '2005' ELSE '2005Plus' END AS MajorVersion"""
-    ).fetchone()
-    mssql_version = result[0]
-    return mssql_version not in ("2000", "2005")
-
-
-def _get_timestamp(conn):
-    dialect_name = conn.dialect.name
-    if dialect_name == "mysql":
-        return mysql.TIMESTAMP(fsp=6, timezone=True)
-    if dialect_name != "mssql":
-        return TIMESTAMP(timezone=True)
-    if _use_date_time2(conn):
-        return mssql.DATETIME2(precision=6)
-    return mssql.DATETIME
-
-
 def upgrade():
     """Apply data_interval fields to DagModel and DagRun."""
-    column_type = _get_timestamp(op.get_bind())
     with op.batch_alter_table("dag_run") as batch_op:
-        batch_op.add_column(Column("data_interval_start", column_type))
-        batch_op.add_column(Column("data_interval_end", column_type))
+        batch_op.add_column(Column("data_interval_start", TIMESTAMP))
+        batch_op.add_column(Column("data_interval_end", TIMESTAMP))
     with op.batch_alter_table("dag") as batch_op:
-        batch_op.add_column(Column("next_dagrun_data_interval_start", column_type))
-        batch_op.add_column(Column("next_dagrun_data_interval_end", column_type))
+        batch_op.add_column(Column("next_dagrun_data_interval_start", TIMESTAMP))
+        batch_op.add_column(Column("next_dagrun_data_interval_end", TIMESTAMP))
 
 
 def downgrade():

airflow/migrations/versions/1b38cef5b76e_add_dagrun.py

@@ -27,7 +27,7 @@
 import sqlalchemy as sa
 from alembic import op
 
-from airflow.models.base import COLLATION_ARGS
+from airflow.migrations.db_types import StringID
 
 # revision identifiers, used by Alembic.
 revision = '1b38cef5b76e'
@@ -40,10 +40,10 @@ def upgrade():
     op.create_table(
         'dag_run',
         sa.Column('id', sa.Integer(), nullable=False),
-        sa.Column('dag_id', sa.String(length=250, **COLLATION_ARGS), nullable=True),
+        sa.Column('dag_id', StringID(), nullable=True),
         sa.Column('execution_date', sa.DateTime(), nullable=True),
         sa.Column('state', sa.String(length=50), nullable=True),
-        sa.Column('run_id', sa.String(length=250, **COLLATION_ARGS), nullable=True),
+        sa.Column('run_id', StringID(), nullable=True),
         sa.Column('external_trigger', sa.Boolean(), nullable=True),
         sa.PrimaryKeyConstraint('id'),
         sa.UniqueConstraint('dag_id', 'execution_date'),

airflow/migrations/versions/3c20cacc0044_add_dagrun_run_type.py

@@ -31,7 +31,7 @@
 from sqlalchemy.engine.reflection import Inspector
 from sqlalchemy.ext.declarative import declarative_base
 
-from airflow.models.base import ID_LEN
+from airflow.migrations.db_types import StringID
 from airflow.utils import timezone
 from airflow.utils.sqlalchemy import UtcDateTime
 from airflow.utils.state import State
@@ -55,12 +55,12 @@ class DagRun(Base):  # type: ignore
     __tablename__ = "dag_run"
 
     id = Column(Integer, primary_key=True)
-    dag_id = Column(String(ID_LEN))
+    dag_id = Column(StringID())
     execution_date = Column(UtcDateTime, default=timezone.utcnow)
     start_date = Column(UtcDateTime, default=timezone.utcnow)
     end_date = Column(UtcDateTime)
     _state = Column('state', String(50), default=State.RUNNING)
-    run_id = Column(String(ID_LEN))
+    run_id = Column(StringID())
     external_trigger = Column(Boolean, default=True)
     run_type = Column(String(50), nullable=False)
     conf = Column(PickleType)
@@ -96,7 +96,9 @@ def upgrade():
 
         # Make run_type not nullable
         with op.batch_alter_table("dag_run") as batch_op:
-            batch_op.alter_column("run_type", type_=run_type_col_type, nullable=False)
+            batch_op.alter_column(
+                "run_type", existing_type=run_type_col_type, type_=run_type_col_type, nullable=False
+            )
 
 
 def downgrade():

airflow/migrations/versions/64de9cddf6c9_add_task_fails_journal_table.py

@@ -26,7 +26,7 @@
 import sqlalchemy as sa
 from alembic import op
 
-from airflow.models.base import COLLATION_ARGS
+from airflow.migrations.db_types import StringID
 
 # revision identifiers, used by Alembic.
 revision = '64de9cddf6c9'
@@ -39,8 +39,8 @@ def upgrade():
     op.create_table(
         'task_fail',
         sa.Column('id', sa.Integer(), nullable=False),
-        sa.Column('task_id', sa.String(length=250, **COLLATION_ARGS), nullable=False),
-        sa.Column('dag_id', sa.String(length=250, **COLLATION_ARGS), nullable=False),
+        sa.Column('task_id', StringID(), nullable=False),
+        sa.Column('dag_id', StringID(), nullable=False),
         sa.Column('execution_date', sa.DateTime(), nullable=False),
         sa.Column('start_date', sa.DateTime(), nullable=True),
         sa.Column('end_date', sa.DateTime(), nullable=True),

airflow/migrations/versions/6e96a59344a4_make_taskinstance_pool_not_nullable.py

@@ -30,7 +30,7 @@
 from sqlalchemy import Column, Float, Integer, PickleType, String
 from sqlalchemy.ext.declarative import declarative_base
 
-from airflow.models.base import COLLATION_ARGS
+from airflow.migrations.db_types import StringID
 from airflow.utils.session import create_session
 from airflow.utils.sqlalchemy import UtcDateTime
 
@@ -60,8 +60,8 @@ class TaskInstance(Base):  # type: ignore
 
     __tablename__ = "task_instance"
 
-    task_id = Column(String(ID_LEN, **COLLATION_ARGS), primary_key=True)
-    dag_id = Column(String(ID_LEN, **COLLATION_ARGS), primary_key=True)
+    task_id = Column(StringID(), primary_key=True)
+    dag_id = Column(StringID(), primary_key=True)
     execution_date = Column(UtcDateTime, primary_key=True)
     start_date = Column(UtcDateTime)
     end_date = Column(UtcDateTime)

airflow/migrations/versions/7939bcff74ba_add_dagtags_table.py

@@ -27,7 +27,7 @@
 import sqlalchemy as sa
 from alembic import op
 
-from airflow.models.base import COLLATION_ARGS
+from airflow.migrations.db_types import StringID
 
 # revision identifiers, used by Alembic.
 revision = '7939bcff74ba'
@@ -41,7 +41,7 @@ def upgrade():
     op.create_table(
         'dag_tag',
         sa.Column('name', sa.String(length=100), nullable=False),
-        sa.Column('dag_id', sa.String(length=250, **COLLATION_ARGS), nullable=False),
+        sa.Column('dag_id', StringID(), nullable=False),
         sa.ForeignKeyConstraint(
             ['dag_id'],
             ['dag.dag_id'],