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Re: Replacing WebSQL with a Relational Data Model.

From: Jeremy Orlow <jorlow@chromium.org>
Date: Tue, 26 Oct 2010 21:06:27 +0100
Message-ID: <AANLkTi=peYqQPO8txr=jts+X8R2iLMK=Sd45kov7Ubx6@mail.gmail.com>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
Cc: Keean Schupke <keean@fry-it.com>, nathan@webr3.org, public-webapps@w3.org, Jonas Sicking <jonas@sicking.cc>, Arthur Barstow <art.barstow@nokia.com>
On Tue, Oct 26, 2010 at 8:04 PM, Keean Schupke <keean@fry-it.com> wrote:

> Hi,
>
>
>> Likewise, personally all data I use is either in graph or k/v format, and
>> have found (like many others), that primary speed gains come from changing
>> the underlying data model rather than trying to map forwards and backwards
>> between objects, graphs and tabular data in a relational data model, via
>> SQL.
>>
>>
>
> If we see HTML5 as a replacement for native mobile apps, and desktop apps,
> then we have to look at what applications require in terms of data storage
> not websites. SQL is very widely used, and that must tell us something.
> Nearly all our apps use it.
>
> Lets think about what is currently done on the server. Lots of server apps
> use a relational database. With HTML5 we would like to move as much of that
> work as possible to the client - so that it uses the client's CPU not the
> servers CPU. The HTML5 app will keep a local cache of some of the server
> database for offline use. For example a calendar app that keeps the next
> months appointments in the client, and allows new meetings to be created
> offline. There may be many ways you wish to seach and cross reference the
> information, for example you may have a contacts table and an appointments
> table. You may use a join to allow the contacts phone number to be displayed
> in each appointment. Searching, sorting, grouping, all things you will want
> to do.
>

On the other hand, what's the first thing most app developers do that use
SQL as a backend?  They use some library that wraps SQL and makes it more
object oriented.  IndexedDB skips this step.  There are definitely pros and
cons to both models.

The problem is the proposed data model is a subset of the functionality
> required. The relational model is a complete algebra (hence the term
> relationally complete). With a non-relationally complete storage API there
> will always be limitations to what it can do.
>

You can implement a relational model on top of IndexedDB, so I'm not sure
what limitations you're talking about except performance.  And this is
something we fully expect we'll need to work on for some time, but I don't
see any fundamental reason performance issues won't be solved since we can
add to the API as we need (while keeping the surface area as small as is
practical!).

What I would like to see is the relational API standardised (maybe in the
> next version of IndexedDB, maybe as a separate standard), so there is a
> relationally complete API available, that browser implementers can implement
> using a relational storage engine like SQLite directly, or can be emulated
> by an implementation on top of IndexedDB where necessary.
>

We will likely implement something, but it'll hopefully be fairly light
weight.  We shouldn't get too ahead of ourselves in speculating about
optimizations until people actually start building real world apps against
IndexedDB though.  I'm hopeful this will start soon as both Mozilla and
WebKit/Chromium's implementations are becoming closer and closer to fully
implementing the spec.


On Tue, Oct 26, 2010 at 8:54 PM, Tab Atkins Jr. <jackalmage@gmail.com>wrote:

> On Tue, Oct 26, 2010 at 12:04 PM, Keean Schupke <keean@fry-it.com> wrote:
> > Take Firefox for example, it implements IndexedDB using SQLite
> apparently.
> > So implementing a relational API if we have to talk to IndexedDB that
> means
> > we have to convert from the relational data model to an object model and
> > then back to a relational model for SQLite. So what I would like to do is
> > punch through that excess layer in the middle and have the relational API
> > talk directly to SQLite in the browser implementation. How could you
> argue
> > that having an unnecessary middle layer is a good thing?
>
> The SQLite back-end used by Firefox's implementation of IndexedDB (and
> Chrome's, for the moment) is unnecessary; at least in Chrome's case,
> we used a SQLite backend only because it was expedient and the code
> was there.  We'll be changing it to a better backend in the future,
> and I suspect that Firefox will do the same in time.
>
> The middle layer isn't unnecessary, *it's the whole point*.  The
> back-end shouldn't ever be exposed directly - you don't want your code
> to break if we drop the SQLite backend and switch to a direct
> b-tree-based backend.
>

...or a fractal tree.  :-P  (Still would love pointers to open
source implementations.)

J
Received on Tuesday, 26 October 2010 20:07:20 GMT

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