airflow/models/base.py

#
# 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.
from __future__ import annotations

from typing import Any

from sqlalchemy import MetaData, String
from sqlalchemy.orm import declarative_base

from airflow.configuration import conf

SQL_ALCHEMY_SCHEMA = conf.get("database", "SQL_ALCHEMY_SCHEMA")

# For more information about what the tokens in the naming convention
# below mean, see:
# https://docs.sqlalchemy.org/en/14/core/metadata.html#sqlalchemy.schema.MetaData.params.naming_convention
naming_convention = {
    "ix": "idx_%(column_0_N_label)s",
    "uq": "%(table_name)s_%(column_0_N_name)s_uq",
    "ck": "ck_%(table_name)s_%(constraint_name)s",
    "fk": "%(table_name)s_%(column_0_name)s_fkey",
    "pk": "%(table_name)s_pkey",
}


def _get_schema():
    if not SQL_ALCHEMY_SCHEMA or SQL_ALCHEMY_SCHEMA.isspace():
        return None
    return SQL_ALCHEMY_SCHEMA


metadata = MetaData(schema=_get_schema(), naming_convention=naming_convention)

Base: Any = declarative_base(metadata=metadata)

ID_LEN = 250


def get_id_collation_args():
    """Get SQLAlchemy args to use for COLLATION."""
    collation = conf.get("database", "sql_engine_collation_for_ids", fallback=None)
    if collation:
        return {"collation": collation}
    else:
        # Automatically use utf8mb3_bin collation for mysql
        # This is backwards-compatible. All our IDS are ASCII anyway so even if
        # we migrate from previously installed database with different collation and we end up mixture of
        # COLLATIONS, it's not a problem whatsoever (and we keep it small enough so that our indexes
        # for MYSQL will not exceed the maximum index size.
        #
        # See https://github.com/apache/airflow/pull/17603#issuecomment-901121618.
        #
        # We cannot use session/dialect as at this point we are trying to determine the right connection
        # parameters, so we use the connection
        conn = conf.get("database", "sql_alchemy_conn", fallback="")
        if conn.startswith("mysql") or conn.startswith("mariadb"):
            return {"collation": "utf8mb3_bin"}
        return {}


COLLATION_ARGS = get_id_collation_args()


def StringID(*, length=ID_LEN, **kwargs) -> String:
    return String(length=length, **kwargs, **COLLATION_ARGS)