airflow/models/base.py

#
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# 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
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# KIND, either express or implied.  See the License for the
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from __future__ import annotations

from typing import TYPE_CHECKING, Any

from sqlalchemy import Column, Integer, MetaData, String, text
from sqlalchemy.orm import registry

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)
mapper_registry = registry(metadata=metadata)
_sentinel = object()

if TYPE_CHECKING:
    Base = Any
else:
    Base = mapper_registry.generate_base()

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", "mariadb")):
            return {"collation": "utf8mb3_bin"}
        return {}


COLLATION_ARGS: dict[str, Any] = get_id_collation_args()


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


class TaskInstanceDependencies(Base):
    """Base class for depending models linked to TaskInstance."""

    __abstract__ = True

    task_id = Column(StringID(), nullable=False)
    dag_id = Column(StringID(), nullable=False)
    run_id = Column(StringID(), nullable=False)
    map_index = Column(Integer, nullable=False, server_default=text("-1"))