From: niklas | brueckenschlaeger <niklas@...>
Date: 2010-11-15T18:16:40+09:00
Subject: Re: Mysql::Result .each_hash - unexpected result

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On Mon, 2010-11-15 at 18:05 +0900, Andy Tolle wrote:
> > One way of solving this would be to keep the results you want to re-use
> > within an array:
> >
> > Hope this helps.
>=20
> Niklas,
>=20
> I'm not too fond using multiple variables to store one thing unless=20
> there is a good reson for it... so I'm wondering: if I question the=20
> Mysql::Result-set, does it then query the database each time I iterate=20
> over his set?

No, the database is not queried every time. The reason I was suggesting
to use an array is that it that that way you don't need to handle that
specially. It works like any other ruby array, unlike the Mysql::Result,
which you need to reset before iterating again. So if you're about to
iterate over the result multiple times, possibly in different places
it's save to either
  a) make your custom iterator, rewinding the result set afterwards=20
    OR
  b) use a standard ruby type, such as Array

a) might look like this (ugly monkey patch):

class Mysql::Result
  def my_each_hash(&block)
    each_hash(&block) ; data_seek(0)
  end
end

Be warned though: this might give you trouble in a threaded environment.

>=20
> Asked differently: you happen to know if storing the resultset in an=20
> array in stead of questioning the resultset over and over, does this=20
> have a positive influence on serverloads?
>=20
> Is there any way I can find out myself when exactly the database is=20
> querried? Seems kinda crucial to optimizing.
>=20


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