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Re: [IndexedDB] What happens when the version changes?

From: Jonas Sicking <jonas@sicking.cc>
Date: Tue, 18 May 2010 01:54:09 -0700
Message-ID: <AANLkTinm_Ikrsup-ZEVGE7FpEap9Hlo9nrSW5si_lNiU@mail.gmail.com>
To: Shawn Wilsher <sdwilsh@mozilla.com>
Cc: Nikunj Mehta <nikunj@o-micron.com>, public-webapps WG <public-webapps@w3.org>
On Thu, May 13, 2010 at 10:25 AM, Shawn Wilsher <sdwilsh@mozilla.com> wrote:
> On 5/13/2010 7:51 AM, Nikunj Mehta wrote:
>>
>> If you search archives you will find a discussion on versioning and that
>> we gave up on doing version management inside the browser and instead leave
>> it to applications to do their own versioning and upgrades.
>
> Right, I'm not saying we should manage it, but I want to make sure we don't
> end up making it very easy for apps to break themselves.  For example:
> 1) Site A has two different tabs (T1 and T2) open that were loaded such that
> one got a script (T1) with a newer indexedDB version than the other (T2).
> 2) T1 upgrades the database in a way that T2 now gets a constraint violation
> on every operation (or some other error due to the database changing).
>
> This could easily happen any time a site changes the version number on their
> database.  As the spec is written right now, there is no way for a site to
> know when the version changes without reopening the database since the
> version property is a sync getter, implementations would have to load it on
> open and cache it, or come up with some way to update all open databases
> (not so fun).

I think what we should do is to make it so that a database connection
is version specific. When you open the database connection (A) the
implementation remembers what version the database had when it was
opened. If another database connection (B) changes the version of the
database, then any requests made to connection A will fail with a
WRONG_VERSION_ERR error.

The implementation must of course wait for any currently executing
transactions in any database connection to finish before changing the
version.

Further the success-callback should likely receive a transaction that
locks the whole database in order to allow the success callback to
actually upgrade the database to the new version format. Not until
this transaction finishes and is committed should new connections be
allowed to be established. These new connections would see the new
database version.

/ Jonas
Received on Tuesday, 18 May 2010 09:03:08 GMT

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