Flask-Migrate hangs on table modificiation

user_3070421 0
Viewed 4183

I have an issue on running the upgrade command with Flask-Migrate. Originally I was trying to modify three tables at once and it hung, I narrowed it down to a specific table (the other upgrades worked without issue). I don't see any locks on the database. I'm using Postgres and just working in a development environment at the moment. The migrate command seems to work fine and generates the upgrade method without any issues (see code)

def upgrade():
    # ### commands auto generated by Alembic - please adjust! ###
    op.drop_column('equipment', 'criteria_notes')
    # ### end Alembic commands ###

Once I run the upgrade command I get stuck here:

>flask db upgrade
INFO  [alembic.runtime.migration] Context impl PostgresqlImpl.
INFO  [alembic.runtime.migration] Will assume transactional DDL.
INFO  [alembic.runtime.migration] Running upgrade 76bf72d8e0e4 -> 1723c01f0606, empty message

with a blinking cursor. When I exit out of the command window (I'm using windows) no changes have been applied.

I've tried

  • Restarting computer
  • Looking for locks or other sessions with pgAdmin
  • Modifying other tables, was able to add and drop columns
flask-migrate postgresql python
4 Answers

You likely have other processes connected to this DB.

This happened to me, I had celery, uwsgi, and a separate custom process all connected to the flask DB on a production server, and I was wonder why the upgrades were hanging.

Once I shut these processes down manually the upgrade script ran fine without hanging.

In my case I also tried rebooting before realizing this, and this did not help because these other processes were programmed to startup on boot.

user_33575870

I had this same issue with MySql due to locks and this command did the trick for me.

sudo service mysql restart
user_110532800

I had the same issue, this one happened to me because of locks,verify it using

select * from pg_locks;

There were many PIDs corresponding to each lock,I restarted the postgresql service then ran the upgrade command it worked

sudo systemctl restart postgresql
flask db upgrade
user_107947570

In my case it was due to locks on the table. 

select * from pg_locks;

in postgres showed me what was happening.

user_43757520
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