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Re: [IndexedDB] Design Flaws: Not Stateless, Not Treating Objects As Opaque

From: Jeremy Orlow <jorlow@chromium.org>
Date: Thu, 31 Mar 2011 11:17:28 -0700
Message-ID: <BANLkTimsZzNtHzftWj2=XW3HBdbojJ=ALw@mail.gmail.com>
To: Keean Schupke <keean@fry-it.com>
Cc: Jonas Sicking <jonas@sicking.cc>, Joran Greef <joran@ronomon.com>, public-webapps@w3.org
On Thu, Mar 31, 2011 at 11:09 AM, Keean Schupke <keean@fry-it.com> wrote:

> On 31 March 2011 17:41, Jonas Sicking <jonas@sicking.cc> wrote:
>
>> On Thu, Mar 31, 2011 at 1:32 AM, Joran Greef <joran@ronomon.com> wrote:
>> > On 31 Mar 2011, at 9:53 AM, Jonas Sicking wrote:
>> >
>> >> I previously have asked for a detailed proposal, but so far you have
>> >> not supplied one but instead keep referring to other unnamed database
>> >> APIs.
>> >
>> > I have already provided an adequate interface proposal for putObject and
>> deleteObject.
>>
>> That is hardly a comprehensive proposal, but rather just one small part of
>> it.
>>
>
> I wanted to make a few comments about these points :-
>
>
>>
>> I do really think the idea of not having the implementation keep track
>> of the set of indexes for a objectStore is a really interesting one.
>> As is the idea of not even having a set set of objectStores. However,
>> there are several problems that needs to be solved. In particular how
>> do you deal with collations?
>>
>
> no indexes, no object stores... well I for one prefer the
> "validate_object_store", "validate_index" approach, in that it can hide
> statefullness if necessary (like I do with RelationalDB) whilst presenting a
> stateless API. It also keeps the size of the put statements down.
>
>
>>
>> I.e. we have concluded that there are important use cases which
>> require using different collations for different indexes and
>> objectStores. Even for different indexes attached to the same
>> objectStore.
>>
>> Additionally, if we're getting rid of setVersion, how do we expect
>> pages dealing with the (application managed) schema changing while the
>> page has a connection open to the database?
>>
>
> 1 - there is no schema
> 2 - dont allow it to change whilst the database is open
>
> In reality a schema is implicitly tied to a code version. In other words
> the source code of the application assumes a certain schema. If the assumed
> schema and the schema in the DB do not match things are going to go very
> wrong very quickly. Schema changes _always_ accompany code changes
> (otherwise they are not schema changes just data changes). As such they
> never happen when a DB is open. The way I handle this in RelationalDB, by
> validating the actual schema against the source-code schema in the db-open
> (actually the method is called validate), is probably the best way to handle
> this. If the database does not exist we create it according to the schema.
> If it exists we check it matches the schema. If there is a difference we see
> if we can 'upgrade' the database automatically (certain changes like adding
> a new column with a default value can be done automaticall), if we cannot
> automaticall upgrade, we exit with an error - as allowing the program to run
> will result in corruption of the data already in the database. At this point
> it is up to the application to figure out how to upgrade the database (by
> opening one database with an old schema and another with a new schema)...
> There is not point in ever allowing a database to be opened with the wrong
> schema.
>
>
>> So pretty please, with sugar on top, please come up with a proposal
>> for the full API rather than bits and pieces.
>>
>> And I should mention that I have as an absolute requirement that you
>> should be able to specify collation by simply saying that you want to
>> use "en-US" or "sv-SV" sorting. Using callbacks or other means is ok
>> *in addition to this*, but callback mechanisms tend to be a lot more
>> complex since they have to deal with the callback doing all sorts of
>> evil things such as returning inconsistent results (think "return
>> Math.random()"), or simply do evil things like navigate the current
>> page, deleting the database, or modifying the record that is in the
>> process of being stored.
>>
>
> The core API only needs to deal with sorting binary-blob sort orders. A
> library wrapper could provide all the collation ordering goodness that
> people want. For example RelationalDB will have to deal with sorting orders,
> it does not need the browser to provide that functionality. In fact browser
> provided functionality may limit what can be done in libraries on top.
>

This is difficult if not impossible to do.  See previous threads on the
matter.

J


>
>
>>
>> / Jonas
>>
>>
>
> Cheers,
> Keean.
>
>
Received on Thursday, 31 March 2011 18:18:18 GMT

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