From: Javier Valencia <jvalencia@...01.org>
Date: 2006-05-21T15:07:48+09:00
Subject: Re: Drb and PStore behaviour

Joel VanderWerf wrote:

>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.
>
>  
>
Interesting point, i'll try it.

And thanks for the correction.