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

From: Keean Schupke <keean@fry-it.com>
Date: Thu, 31 Mar 2011 18:24:57 +0000
Message-ID: <AANLkTimTgrY7LX8L6f=SF_GnAUUhCHVC1xU3Paoyt=W-@mail.gmail.com>
To: Jeremy Orlow <jorlow@chromium.org>
Cc: Jonas Sicking <jonas@sicking.cc>, Joran Greef <joran@ronomon.com>, public-webapps@w3.org
On 31 March 2011 18:17, Jeremy Orlow <jorlow@chromium.org> wrote:

> 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
>

I can find a lot of stuff on collation, but not a lot about why it could not
be done in a library. Could you summerise the reasons why this needs to be
core functionality for me?

A library could chose to use an object store as meta-data to store the
collation orders that it is using for various indexes for example.


Cheers,
Keean.
Received on Thursday, 31 March 2011 18:25:30 GMT

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