From: Joel VanderWerf <vjoel@...>
Date: 2006-05-21T13:12:06+09:00
Subject: Re: Drb and PStore behaviour

Javier Valencia wrote:
> I'm doing a remote database object so i can do:
> 
> result = database.find do |record|
>    record[:name] == "john"
> end
> 
> in the server object i have something like:
> 
> class Foo
>     include DRb::DRbUndumped
> 
>     def find(&block)
               ^^^^^^
You don't need this, since you are using yield.

>             result = nil
>             @store.transaction do
>                     result = @store[:records].find_all do |record|
>                                       yield(record)
>                     end
>             end
>             return result
>     end
> end
> 
> well, the problem is yielding that block. All the database is
> "cloned/copied" (?) over the network when doing the find. I don't want
> to copy all that data, just return the found records.

Yielding to a DRb client is not itself a problem. The block stays on the
client side. In some cases that's ok, but in this case, it generates too
much traffic because every record iterated over by find_all is
serialized to the client, so that the client can call the block on it.

> I tried adding DRb::DRbUndumped to class PStore, but the same result.
> The database size is about 3 MB.

I doubt the database object as a whole is being serialized, just each
record individually.

Maybe you want do define query objects and pass them as an argument to find?

result = database.find(QueryEqual.new(:name, "john"))

Then only the query object and the results need to get serialized.

-- 
      vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407