phppgadmin : How does it kick users out of postgres, so it can db_drop?

I've got one Posgresql database (I'm the owner) and I'd like to drop it and re-create it from a dump.

Problem is, there're a couple applications (two websites, rails and perl) that access the db regularly. So I get a "database is being ac开发者_开发百科cessed by other users" error.

I've read that one possibility is getting the pids of the processes involved and killing them individually. I'd like to do something cleaner, if possible.

Phppgadmin seems to do what I want: I am able to drop schemas using its web interface, even when the websites are on, without getting errors. So I'm investigating how its code works. However, I'm no PHP expert.

I'm trying to understand the phppgadmin code in order to see how it does it. I found out a line (257 in Schemas.php) where it says:

$data->dropSchema(...)

$data is a global variable and I could not find where it is defined.

Any pointers would be greatly appreciated.

First, find all current procesid's using your database:

SELECT usename, procpid FROM pg_stat_activity WHERE datname = current_database();

Second, kill the processes you don't want:

SELECT pg_terminate_backend(your_procpid);

This works as of version 8.4, otherwise pg_terminate_backend() is unknown and you have to kill the process at OS level.

To quickly drop all connections connected to a given database, this shortcut works nicely. Must run as superuser:

SELECT pg_terminate_backend(procpid) FROM pg_stat_activity WHERE datname='YourDB';

On more recent Postgres versions (at least 9.2+, likely earlier), the column names have changed and the query is:

SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE datname='YourDB';

Not sure about PostgreSQL but i think a possible solution would be to lock the table so other processes will fail when they try to access it.

See: http://www.postgresql.org/docs/current/static/sql-lock.html