Error when running `airflow scheduler`

gistfile1.txt

$ airflow scheduler
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____  /| |_  /__  ___/_  /_ __  /_  __ \_ | /| / /
___  ___ |  / _  /   _  __/ _  / / /_/ /_ |/ |/ /
 _/_/  |_/_/  /_/    /_/    /_/  \____/____/|__/
[2020-05-26 11:24:34,913] {__init__.py:51} INFO - Using executor SequentialExecutor
[2020-05-26 11:24:34,918] {scheduler_job.py:1346} INFO - Starting the scheduler
[2020-05-26 11:24:34,918] {scheduler_job.py:1354} INFO - Running execute loop for -1 seconds
[2020-05-26 11:24:34,918] {scheduler_job.py:1355} INFO - Processing each file at most -1 times
[2020-05-26 11:24:34,918] {scheduler_job.py:1358} INFO - Searching for files in /Users/anhtnguyen/airflow/dags
[2020-05-26 11:24:34,920] {scheduler_job.py:1360} INFO - There are 2 files in /Users/anhtnguyen/airflow/dags
[2020-05-26 11:24:34,920] {scheduler_job.py:1411} INFO - Resetting orphaned tasks for active dag runs
[2020-05-26 11:24:34,924] {scheduler_job.py:1384} ERROR - Exception when executing execute_helper
Traceback (most recent call last):
  File "/Users/anhtnguyen/tfx-env/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1284, in _execute_context
    cursor, statement, parameters, context
  File "/Users/anhtnguyen/tfx-env/lib/python3.6/site-packages/sqlalchemy/engine/default.py", line 590, in do_execute
    cursor.execute(statement, parameters)
sqlite3.OperationalError: no such column: task_instance.pool_slots

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/Users/anhtnguyen/tfx-env/lib/python3.6/site-packages/airflow/jobs/scheduler_job.py", line 1382, in _execute
    self._execute_helper()
  File "/Users/anhtnguyen/tfx-env/lib/python3.6/site-packages/airflow/jobs/scheduler_job.py", line 1412, in _execute_helper
    self.reset_state_for_orphaned_tasks()
  File "/Users/anhtnguyen/tfx-env/lib/python3.6/site-packages/airflow/utils/db.py", line 74, in wrapper
    return func(*args, **kwargs)
  File "/Users/anhtnguyen/tfx-env/lib/python3.6/site-packages/airflow/jobs/base_job.py", line 276, in reset_state_for_orphaned_tasks
    TI.state.in_(resettable_states))).all()
  File "/Users/anhtnguyen/tfx-env/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 3319, in all
    return list(self)
  File "/Users/anhtnguyen/tfx-env/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 3481, in __iter__
    return self._execute_and_instances(context)
  File "/Users/anhtnguyen/tfx-env/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 3506, in _execute_and_instances
    result = conn.execute(querycontext.statement, self._params)
  File "/Users/anhtnguyen/tfx-env/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1020, in execute
    return meth(self, multiparams, params)
  File "/Users/anhtnguyen/tfx-env/lib/python3.6/site-packages/sqlalchemy/sql/elements.py", line 298, in _execute_on_connection
    return connection._execute_clauseelement(self, multiparams, params)
  File "/Users/anhtnguyen/tfx-env/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1139, in _execute_clauseelement
    distilled_params,
  File "/Users/anhtnguyen/tfx-env/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1324, in _execute_context
    e, statement, parameters, cursor, context
  File "/Users/anhtnguyen/tfx-env/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1518, in _handle_dbapi_exception
    sqlalchemy_exception, with_traceback=exc_info[2], from_=e
  File "/Users/anhtnguyen/tfx-env/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 178, in raise_
    raise exception
  File "/Users/anhtnguyen/tfx-env/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1284, in _execute_context
    cursor, statement, parameters, context
  File "/Users/anhtnguyen/tfx-env/lib/python3.6/site-packages/sqlalchemy/engine/default.py", line 590, in do_execute
    cursor.execute(statement, parameters)
sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) no such column: task_instance.pool_slots
[SQL: SELECT task_instance.try_number AS task_instance_try_number, task_instance.task_id AS task_instance_task_id, task_instance.dag_id AS task_instance_dag_id, task_instance.execution_date AS task_instance_execution_date, task_instance.start_date AS task_instance_start_date, task_instance.end_date AS task_instance_end_date, task_instance.duration AS task_instance_duration, task_instance.state AS task_instance_state, task_instance.max_tries AS task_instance_max_tries, task_instance.hostname AS task_instance_hostname, task_instance.unixname AS task_instance_unixname, task_instance.job_id AS task_instance_job_id, task_instance.pool AS task_instance_pool, task_instance.pool_slots AS task_instance_pool_slots, task_instance.queue AS task_instance_queue, task_instance.priority_weight AS task_instance_priority_weight, task_instance.operator AS task_instance_operator, task_instance.queued_dttm AS task_instance_queued_dttm, task_instance.pid AS task_instance_pid, task_instance.executor_config AS task_instance_executor_config 
FROM task_instance JOIN dag_run ON task_instance.dag_id = dag_run.dag_id AND task_instance.execution_date = dag_run.execution_date 
WHERE dag_run.state = ? AND dag_run.run_id NOT LIKE ? AND task_instance.state IN (?, ?)]
[parameters: ('running', 'backfill_%', 'scheduled', 'queued')]
(Background on this error at: http://sqlalche.me/e/e3q8)
[2020-05-26 11:24:34,928] {dag_processing.py:705} WARNING - Ending without manager process.
[2020-05-26 11:24:34,929] {scheduler_job.py:1387} INFO - Exited execute loop