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"""Change default ``pool_slots`` to ``1``

Revision ID: 8646922c8a04
Revises: 449b4072c2da
Create Date: 2021-02-23 23:19:22.409973

"""

import sqlalchemy as sa
from alembic import op

# revision identifiers, used by Alembic.
revision = '8646922c8a04'
down_revision = '449b4072c2da'
branch_labels = None
depends_on = None
airflow_version = '2.0.2'


def upgrade():
    """Change default ``pool_slots`` to ``1`` and make pool_slots not nullable"""
    op.execute("UPDATE task_instance SET pool_slots = 1 WHERE pool_slots IS NULL")
    with op.batch_alter_table("task_instance", schema=None) as batch_op:
        batch_op.alter_column("pool_slots", existing_type=sa.Integer, nullable=False, server_default='1')


def downgrade():
    """Unapply Change default ``pool_slots`` to ``1``"""
    with op.batch_alter_table("task_instance", schema=None) as batch_op:
        batch_op.alter_column("pool_slots", existing_type=sa.Integer, nullable=True, server_default=None)
