relation "pg_hero_connections" does not exist about pghero

[ankane]

PgHero creates a PgHero::Connection model without a table. It's a bit of a hack but haven't found a better way to do it. Is it causing issues for your application?

[manuelmeurer]

Yes it does since I need to call ActiveRecord::Base.descendants at one point and then it complaints about the missing table.
What is Connection really needed for? It seems like establish_connection, connection_config and other methods can be called on ActiveRecord::Base as well, or am I missing something?

[ankane]

The model allows you to set ENV["PGHERO_DATABASE_URL"] to use a different user or database than your application. Does:

ActiveRecord::Base.descendants.reject{|d| d == PgHero::Connection }

do the trick?

[manuelmeurer]

Nope, that generates the same error. I think the solution is to not inherit from ActiveRecord::Base but just include/extend the necessary modules like this:

class Connection
  extend ActiveRecord::ConnectionHandling
  include ActiveRecord::Core
end

(and maybe a few more are needed)

Then you would need to call Connection.establish_connection explicitly before accessing the connection the first time.
Unfortunately I don't have a lot of time to test this out right now but I think it's the right direction. 😄

[kmarshall008]

Hi @manuelmeurer and @ankane,

Do you have any sense why my rails production app on heroku is having a similar issue, which is causing severe memory leaks?

The following two SQL statements are consuming 99% of my apps memory in production app on heroku.

SELECT a.attname, format_type(a.atttypid, a.atttypmod), pg_get_expr(d.adbin, d.adrelid), a.attnotnull,     a.atttypid, a.atttypmod FROM pg_attribute a LEFT JOIN pg_attrdef d ON a.attrelid = d.adrelid AND a.attnum = d.adnum WHERE a.attrelid = ?::regclass AND a.attnum > ? AND NOT a.attisdropped ORDER BY a.attnum

SELECT t.oid, t.typname, t.typelem, t.typdelim, t.typinput, r.rngsubtype, t.typtype, t.typbasetype FROM pg_type as t LEFT JOIN pg_range as r ON oid = rngtypid

My db:rake config file is as follows:

namespace :db do
  desc "Fix 'database is being accessed by other users'"
  task :terminate => :environment do
    ActiveRecord::Base.connection.execute <<-SQL
      SELECT
        pg_terminate_backend(pid)
      FROM
        pg_stat_activity
      WHERE
        -- don't kill my own connection!
        pid <> pg_backend_pid()
        -- don't kill the connections to other databases
        AND datname = '#{ActiveRecord::Base.connection.current_database}';
    SQL
  end
end
Rake::Task["db:drop"].enhance ["db:terminate"]

I think that what I need to do is create this new class, update my puma.rb file to explicitly point to it and then re-build my production app.

But... do you think I'm barking up the right tree?

Thanks much

[manuelmeurer]

@kmarshall008 what does this have to do with the issue I reported, let alone PgHero at all?

[ankane]

@manuelmeurer Can you try master? 3f1570c

gem 'pghero', github: 'ankane/pghero'

[manuelmeurer]

Works!