new_contents: """empty message
  
  Revision ID: 306f880b11c3
  Revises: 255f81eff867
  Create Date: 2018-08-03 15:07:44.354557
  
  """
  import sqlalchemy as sa
  from alembic import op
  
  # revision identifiers, used by Alembic.
  revision = '306f880b11c3'
  down_revision = '255f81eff867'
  branch_labels = None
  depends_on = None
  
  
  def upgrade():
      op.execute("UPDATE cluster \
              SET description='Spark local - 1 core / 1GB RAM', \
              address='local[*]',  \
              executor_cores=1,  \
              executor_memory='1G',  \
              executors=1  \
              WHERE id=1;")
  
  def downgrade():
      op.execute("UPDATE cluster \
              SET description='Default cluster - change it', \
              address='localhost',  \
              executor_cores=0,  \
              executor_memory='',  \
              executors=0  \
              WHERE id=1;")
  
subject: Update cluster database to make local spark work