From: Eric Sven Ristad <ristad@...>
Date: 2001-03-04T19:50:48+09:00
Subject: [ruby-talk:11969] Ruby/MySql garbage collection problem

I've written a Ruby program that uses Tomita Masahiro's excellent
ruby-mysql module to communicate with a MySql database.  Unfortunately
if the program runs for a while, it runs out of memory and crashes.
It looks like the problem is that the garbage collector is not getting
called often enough to reclaim the results of the mysql queries made
by my Ruby program.

The following small program illustrates the problem:

require "mysql"
def leak(n,do_free)
  db = Mysql.new("host",nil,nil,"test")
  db.query("CREATE TEMPORARY TABLE RubyTest ( bogus INT NOT NULL )")
  n.times{
    result = db.query("SELECT bogus from RubyTest")
    result.free if do_free
  }
  db.close
end

If I run leak(*,false) in irb then the amount of memory consumed by
the irb process increases every time leak(*,false) is called.

irb>				4.59M
irb> load "leak.rb"		5.86M
irb> leak(100,false)		6.69M
irb> leak(1000,false)		15.0M
irb> leak(10000,false)		19.2M

But if I run leak(*,true) in irb then the amount of memory consumed by
the irb process remains roughly constant.

irb>				4.59M
irb> load "leak.rb"		5.86M
irb> leak(100,true)		5.94M
irb> leak(1000,true)		5.94M
irb> leak(10000,true)		5.94M

Explicit calls to Mysqlres#free are ugly; I would much rather if the
garbage collector did that work for me.  How can I make sure the
garbage collector gets called before the process runs out of memory?

Thanks,
Eric