Rails + Postgres drop error: database is being accessed by other users

Question

I have a rails application running over Postgres.

I have two servers: one for testing and the other for production.

Very often I need to clone the production

Answer 1

After restarting the server or computer, please try again.

It could be the simple solution.

Answer 2

Please check if your rails console or server is running in another tab and then

stop the rails server and console.

then run

 rake db:drop

Answer 3

When we used the "kill processes" method from above, the db:drop was failing (if :kill_postgres_connections was prerequisite). I believe it was because the connection which that rake command was using was being killed. Instead, we are using a sql command to drop the connection. This works as a prerequisite for db:drop, avoids the risk of killing processes via a rather complex command, and it should work on any OS (gentoo required different syntax for kill).

cmd = %(psql -c "SELECT pg_terminate_backend(procpid) FROM pg_stat_activity WHERE procpid <> pg_backend_pid();" -d '#{db_name}')

Here is a rake task that reads the database name from database.yml and runs an improved (IMHO) command. It also adds db:kill_postgres_connections as a prerequisite to db:drop. It includes a warning that yells after you upgrade rails, indicating that this patch may no longer be needed.

see: https://gist.github.com/4455341, references included

Answer 4

I had this same issue when working with a Rails 5.2 application and PostgreSQL database in production.

Here's how I solved it:

First, log out every connection to the database server on the PGAdmin Client if any.

Stop every session using the database from the terminal.

sudo kill -9 `ps -u postgres -o pid=`

Start the PostgreSQL server, since the kill operation above stopped the PostgreSQL server.

sudo systemctl start postgresql

Drop the database in the production environment appending the production arguments.

rails db:drop RAILS_ENV=production DISABLE_DATABASE_ENVIRONMENT_CHECK=1

That's all.

I hope this helps

Answer 5

If you kill the running postgresql connections for your application, you can then run db:drop just fine. So how to kill those connections? I use the following rake task:

# lib/tasks/kill_postgres_connections.rake
task :kill_postgres_connections => :environment do
  db_name = "#{File.basename(Rails.root)}_#{Rails.env}"
  sh = <<EOF
ps xa \
  | grep postgres: \
  | grep #{db_name} \
  | grep -v grep \
  | awk '{print $1}' \
  | xargs kill
EOF
  puts `#{sh}`
end

task "db:drop" => :kill_postgres_connections

Killing the connections out from under rails will sometimes cause it to barf the next time you try to load a page, but reloading it again re-establishes the connection.

Answer 6

Easier and more updated way is: 1. Use ps -ef | grep postgres to find the connection # 2. sudo kill -9 "# of the connection

Note: There may be identical PID. Killing one kills all.