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HBase >> mail # dev >> adding constraints


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Re: adding constraints
On Mon, Oct 17, 2011 at 11:00 AM, Ted Yu <[EMAIL PROTECTED]> wrote:

> Jesse:
> This is a nice initiative.
> Looks like the Constraint you define below is per table. Meaning it is not
> cross-table referential integrity.
>

Theoretically we could support doing this. And if people were really cheeky
with the current implementation, they could access other tables to enforce
it (though it would kill you on access time). Even so, doing the cross-table
checks, is going to be rough on run time (cross-server locking is always bad
news bears ;), so thinking this should definitely be a later consideration.
> Cheers
>
> On Mon, Oct 17, 2011 at 10:45 AM, Jesse Yates <[EMAIL PROTECTED]
> >wrote:
>
> > Hey everyone,
> >
> > TL;DR Adding classic DB constraints as a system level coprocessor to help
> > simplify using HBase and ease adopting.
> >
> > Coprocessors are a really powerful mechanism and are incredibly useful
> for
> > a
> > variety of things. However, I feel like the mechanism for using them can
> be
> > very daunting and, for certain features, could do with some
> simplification.
> >
> > What I would like to propose is a simple interface that people can use to
> > implement a 'constraint' (matching the classic database definition). This
> > would help ease of adoption by helping HBase more easily check that box,
> > help minimize code duplication across organizations, and lead to easier
> > adoption.
> >
> > Essentially, people would implement a 'Constraint' interface for checking
> > keys before they are put into a table. Puts that are valid get written to
> > the table, but if not people can will throw an exception that gets
> > propagated back to the client explaining why the put was invalid.
> >
> > Constraints would be set on a per-table basis and the user would be
> > expected
> > to ensure the jars containing the constraint are present on the machines
> > serving that table.
> >
> > Yes, people could roll their own mechanism for doing this via
> coprocessors
> > each time, but this would make it easier to do so, so you only have to
> > implement a very minimal interface and not worry about the specifics.
> >
> > If people are interested, I would like to open a Jira on the feature.
> I've
> > got a basic implementation, but would like to expand it to be a more
> > integrated, top-level element of the code. I just don't want to waste my
> > time doing a full blown impl and then not have at least general concensus
> > on
> > it being a good feature.
> >
> > One of the complaints I commonly hear about HBase is that, to outsiders,
> it
> > is difficult to figure out and use (though once you do, its solid). This
> > would be a step to make it easier to use and adopt.
> >
> > Thanks,
> > Jesse Yates
> >
>