old_contents: from flask.cli import AppGroup
  from flask_migrate import stamp
  manager = AppGroup(help="Manage the database (create/drop tables).")
  
  
  @manager.command()
  def create_tables():
      """Create the database tables."""
      from redash.models import db
      db.create_all()
  
      # Need to mark current DB as up to date
      stamp()
  
  
  @manager.command()
  def drop_tables():
      """Drop the database tables."""
      from redash.models import db
  
      db.drop_all()
  
new_contents: import time
  
  from flask.cli import AppGroup
  from flask_migrate import stamp
  from sqlalchemy.exc import DatabaseError
  
  manager = AppGroup(help="Manage the database (create/drop tables).")
  
  
  def _wait_for_db_connection(db):
      retried = False
      while not retried:
          try:
              db.engine.execute('SELECT 1;')
              return
          except DatabaseError:
              time.sleep(30)
  
          retried = True
  
  
  @manager.command()
  def create_tables():
      """Create the database tables."""
      from redash.models import db
  
      _wait_for_db_connection(db)
      db.create_all()
  
      # Need to mark current DB as up to date
      stamp()
  
  
  @manager.command()
  def drop_tables():
      """Drop the database tables."""
      from redash.models import db
  
      _wait_for_db_connection(db)
      db.drop_all()
  
subject: Fix connection error when you run "create_tables"