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From: ramkrishna vasudevan <ramkrishna.s.vasudevan@gmail.com>
Date: Fri, 29 Sep 2017 14:27:44 +0530
Message-ID: <CAAT7MkpamZHjgT56iZ85ud8=tD_X=ooWDdnqqPcF+yvnsV4uiQ@mail.gmail.com>
Subject: Re: [DISCUSS] Move Type out of KeyValue
To: "dev@hbase.apache.org" <dev@hbase.apache.org>
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archived-at: Fri, 29 Sep 2017 08:57:52 -0000

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Even if we are trying to move out I think only few of the types are really
user readable. So we should be very careful here. So since we have
CellBuilder way it is better we check what type of cells a user can build.
I think for now the Cellbuilder is not client exposed?
But again moving to Cell means it becomes public which is not right IMO and
I thinks others here also agree to it.

Regards
Ram

On Fri, Sep 29, 2017 at 10:50 AM, Chia-Ping Tsai <chia7712@apache.org>
wrote:

> Thanks for all comment.
>
> The problem i want to resolve is the valid code should be exposed as
> IA.Public. Otherwise, end user have to access the IA.Private class to build
> the custom cell.
>
> For example, I have a use case which plays a streaming role in our
> appliaction. It
> applies the CellBuilder(HBASE-18519) to build custom cells. These cells
> have many same fields so they are put in shared-memory for avoiding GC
> pause. Everything is wonderful. However, we have to access the IA.Private
> class - KeyValue#Type - to get the valid code of Put.
>
> I believe there are many use cases of custom cell, and consequently it is
> worth adding a way to get the valid type via IA.Public class. Otherwise, it
> may imply that the custom cell is based on a unstable way, because the
> related code can be changed at any time.
> --
> Chia-Ping
>
> On 2017-09-29 00:49, Andrew Purtell <apurtell@apache.org> wrote:
> > I agree with Stack. Was typing up a reply to Anoop but let me move it
> down
> > here.
> >
> > The type code exposes some low level details of how our current stores
> are
> > architected. But what if in the future you could swap out HStore
> implements
> > Store with PStore implements Store, where HStore is backed by HFiles and
> > PStore is backed by Parquet? Just as a hypothetical example. I know there
> > would be larger issues if this were actually attempted. Bear with me. You
> > can imagine some different new Store implementation that has some
> > advantages but is not a design derived from the log structured merge tree
> > if you like. Most values from a new Cell.Type based on KeyValue.Type
> > wouldn't apply to cells from such a thing because they are particular to
> > how LSMs work. I'm sure such a project if attempted would make a number
> of
> > changes requiring a major version increment and low level details could
> be
> > unwound from Cell then, but if we could avoid doing it in the first
> place,
> > I think it would better for maintainability.
> >
> >
> > On Thu, Sep 28, 2017 at 9:39 AM, Stack <stack@duboce.net> wrote:
> >
> > > On Thu, Sep 28, 2017 at 2:25 AM, Chia-Ping Tsai <chia7712@apache.org>
> > > wrote:
> > >
> > > > hi folks,
> > > >
> > > > User is allowed to create custom cell but the valid code of type -
> > > > KeyValue#Type - is declared as IA.Private. As i see it, we should
> expose
> > > > KeyValue#Type as Public Client. Three possible ways are shown below:
> > > > 1) Change declaration of KeyValue#Type from IA.Private to IA.Public
> > > > 2) Move KeyValue#Type into Cell.
> > > > 3) Move KeyValue#Type to upper level
> > > >
> > > > Any suggestions?
> > > >
> > > >
> > > What is the problem that we are trying to solve Chia-Ping? You want to
> make
> > > Cells of a new Type?
> > >
> > > My first reaction is that KV#Type is particular to the KV
> implementation.
> > > Any new Cell implementation should not have to adopt the KeyValue
> typing
> > > mechanism.
> > >
> > > S
> > >
> > >
> > >
> > >
> > > > --
> > > > Chia-Ping
> > > >
> > > >
> > >
> >
> >
> >
> > --
> > Best regards,
> > Andrew
> >
> > Words like orphans lost among the crosstalk, meaning torn from truth's
> > decrepit hands
> >    - A23, Crosstalk
> >
>

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