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From David Van Couvering <David.Vancouver...@Sun.COM>
Subject Re: New "segmented" StorageFactory Development
Date Fri, 05 May 2006 17:48:58 GMT
Hi, Rodrigo.  Hopefully you took no offense.  It was a tease at the 
debate going on the derby-user alias.  It's *great* to have you working 
on this, absolutely, I'm quite excited, this is something people 
regularly ask for.

David

Rodrigo Madera wrote:
> Well, please, I'm not related to the Derby project at all.
> 
> I work at IBM Brazil, on a client services project for Medco. Nothing
> to do with Derby.
> 
> Rodrigo
> 
> On 5/5/06, David Van Couvering <David.Vancouvering@sun.com> wrote:
>> Oh, wait, how could you be working for IBM and adding a feature?  I
>> thought you guys were only doing bugfixes :)
>>
>> David
>>
>> Rodrigo Madera wrote:
>> > Oh, just a technical detail... I work for IBM, but on a whole
>> > different project...
>> >
>> > Is this a problem??
>> >
>> > Thanks
>> >
>> > On 5/5/06, Rodrigo Madera <rodrigo.madera@gmail.com> wrote:
>> >> On 5/5/06, Mike Matrigali <mikem_app@sbcglobal.net> wrote:
>> >> > Do you have any more details on your requirements, such as the
>> >> following:
>> >> > 1) do you need for a single table and/or index to be spread across
>> >> >     multiple disk?
>> >>
>> >> It would be terrific and the absolute glory of the requirement,
>> >> however, it depends.
>> >>
>> >> Is Derby based on a table/index-is-a-single-file architecture? If so,
>> >> it's too much trouble to change this. Making the tables/indexes
>> >> segmented would only be viable (in my opinion) if Derby already
>> >> supports this.
>> >>
>> >> I vote to get the "divider" in place that routes the new tables/etc to
>> >> the different directories, and only then, when it's mature, begin a
>> >> table segmentation engine.
>> >>
>> >> > 2) do you want control when you create each table/index where it
>> >> >     goes and how?
>> >>
>> >> Yes. I'm planing on doing this automagicaly based on the specified
>> >> directory/capacity pairs.
>> >>
>> >> > 3) Are you looking to limit the absolute size of tables/indexes
>> >> >     in each directory to a fixed size?
>> >>
>> >> Absolutely. This is very important for the approach I'm thinking of in
>> >> #1.
>> >>
>> >> > The existing storage system had some support for spreading data
>> >> > across disks built into the interfaces, but was never used.  Data
>> >> > is currently stored in the seg0 directory.  The idea was that
>> >> > support could be added to store data also in a seg1 directory
>> >> > located on another device.  If one were interested in this approach
>> >> > they would first have to fix the code to pass around correctly
>> >> > the seg argument (It has been observed that some code got lazy and
>> >> > just used 0 rather than proprogating the argument).
>> >>
>> >> I'm in. I'll co the latest version and check it out. Is it still 
>> there?
>> >>
>> >> > The next decision is how the tables are to spread across the disks.
>> >> > If putting whole tables or indexes fits your plan then I would use
>> >> > the existing table metadata catalogs to track where a file is (these
>> >> > may have to be upgraded to hold the new info - not sure).
>> >>
>> >> IMO: This is the way to go for now.
>> >>
>> >> >  If one
>> >> > wants to spread a single file across multiple segments then you need
>> >> > to decide if you want to do it by key or by some mathematical block
>> >> > number approach:
>> >> >
>> >> > partition by key
>> >> >     o would pave the road for future interesting parallel query
>> >> >       execution work.
>> >> >     o would recommend again top down implementation, having the
>> >> >       existing database metadata catalogs do the work.
>> >> >
>> >> > partition by block number
>> >> >     o If there is any per table/index control again use the existing
>> >> >       database metadata catalogs and pass the info down into
>> >> >       store. partitioning by block number probably would best be 
>> done
>> >> >       with some new module as Dan suggested with alternate storage
>> >> >       factory implementations.
>> >>
>> >> Too messy for now... Guess #1 is better for now...
>> >>
>> >> > If you want per table/index control I think the segX approach is the
>> >> > best, since the obvious input would be from the create table 
>> command.
>> >>
>> >> Ok. But I preffer to have the array of {path, capacity} tuples (or
>> >> table, or meta info, or ...).
>> >>
>> >> > If you rather do the bottom up approach, I would first start at 
>> looking
>> >> > at the in memory patch that was done.  If you don't need much per
>> >> > file control it may be possible to only override the 
>> StorageFactory as
>> >> > Dan described.
>> >>
>> >> I'll take a look at it immediately.
>> >>
>> >> > Whatever approach you pick a couple of issues come to mind:
>> >> > o how do you config the new segements into the db (currently just
>> >> > automatically done a db creation time).
>> >>
>> >> Via the configuration tuples.
>> >>
>> >> > o how do back up a multiple segment database
>> >>
>> >> Transversing the repositories.
>> >>
>> >> > o how do handle allocation of disk space to files, current model
>> >> >    is the db just uses all the disk space available on that disk and
>> >> >    fails if table allocation gets and out of disk space.
>> >>
>> >> DB uses all ${capacity} on ${path}.
>> >>
>> >>
>> >>
>> >> This is only my initial vision of the model, so please give your
>> >> opinions here to make it better.
>> >>
>> >> Thanks,
>> >> Rodrigo Madera
>> >>
>>

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