SELECT 
pg_terminate_backend(pid) 
FROM 
pg_stat_activity 
WHERE
pid <> pg_backend_pid()
-- no need to kill connections to other databases
AND datname = current_database();
-- use current_database by opening right query tool

打开PGadmin查看是否有任何查询页面打开，关闭所有查询页面，断开PostgresSQL服务器连接，重新连接，尝试删除/删除选项。这对我很有帮助。

我是这样解决的:

在我的Windows8 64位，只是重新启动服务:postgresql-x64-9.5

MacOS，如果postgresql安装了brew:

brew services restart postgresql

UBUNTU,

首先用这个检查(在后台运行的kill服务器)

sudo kill -9 $(lsof -i :3000 -t)

如果你没有找到pid，那么你只需要重新启动 Postgresql服务的命令如下所示:

sudo service postgresql restart

这似乎适用于PostgreSQL 9.1:

#{Rails.root}/lib/tasks/databases.rake
# monkey patch ActiveRecord to avoid There are n other session(s) using the database.
def drop_database(config)
  case config['adapter']
  when /mysql/
    ActiveRecord::Base.establish_connection(config)
    ActiveRecord::Base.connection.drop_database config['database']
  when /sqlite/
    require 'pathname'
    path = Pathname.new(config['database'])
    file = path.absolute? ? path.to_s : File.join(Rails.root, path)

    FileUtils.rm(file)
  when /postgresql/
    ActiveRecord::Base.establish_connection(config.merge('database' => 'postgres', 'schema_search_path' => 'public'))
    ActiveRecord::Base.connection.select_all("select * from pg_stat_activity order by procpid;").each do |x|
      if config['database'] == x['datname'] && x['current_query'] =~ /<IDLE>/
        ActiveRecord::Base.connection.execute("select pg_terminate_backend(#{x['procpid']})")
      end
    end
    ActiveRecord::Base.connection.drop_database config['database']
  end
end

从这里和这里的胃肠道谱上提取的。

下面是一个修改后的版本，适用于PostgreSQL 9.1和9.2。

关于运行进程的所有信息:

SELECT *, pg_terminate_backend(pid)
FROM pg_stat_activity 
WHERE pid <> pg_backend_pid()
AND datname = 'my_database_name';