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Re: [Bug 11351] New: [IndexedDB] Should we have a maximum key size (or something like that)?

From: Jonas Sicking <jonas@sicking.cc>
Date: Sun, 6 Feb 2011 23:38:13 -0800
Message-ID: <AANLkTikmaPdMOA1o2uBnaXQ8_v9MQJTrocLqRYLudBZ9@mail.gmail.com>
To: Jeremy Orlow <jorlow@chromium.org>
Cc: Shawn Wilsher <sdwilsh@mozilla.com>, Pablo Castro <Pablo.Castro@microsoft.com>, "public-webapps@w3.org" <public-webapps@w3.org>
On Sun, Feb 6, 2011 at 2:31 PM, Jeremy Orlow <jorlow@chromium.org> wrote:
> On Sun, Feb 6, 2011 at 2:03 PM, Shawn Wilsher <sdwilsh@mozilla.com> wrote:
>>
>> On 2/6/2011 12:42 PM, Jeremy Orlow wrote:
>>>
>>> My current thinking is that we should have some relatively large
>>> limit....maybe on the order of 64k?  It seems like it'd be very difficult
>>> to
>>> hit such a limit with any sort of legitimate use case, and the chances of
>>> some subtle data-dependent error would be much less.  But a 1GB key is
>>> just
>>> not going to work well in any implementation (if it doesn't simply oom
>>> the
>>> process!).  So despite what I said earlier, I guess I think we should
>>> have
>>> some limit...but keep it an order of magnitude or two larger than what we
>>> expect any legitimate usage to hit just to keep the system as flexible as
>>> possible.
>>>
>>> Does that sound reasonable to people?
>>
>> Are we thinking about making this a MUST requirement, or a SHOULD?  I'm
>> hesitant to spec an exact size as a MUST given how technology has a way of
>> changing in unexpected ways that makes old constraints obsolete.  But then,
>> I may just be overly concerned about this too.
>
> If we put a limit, it'd be a MUST for sure.  Otherwise people would develop
> against one of the implementations that don't place a limit and then their
> app would break on the others.
> The reason that I suggested 64K is that it seems outrageously big for the
> data types that we're looking at.  But it's too small to do much with base64
> encoding binary blobs into it or anything else like that that I could see
> becoming rather large.  So it seems like a limit that'd avoid major abuses
> (where someone is probably approaching the problem wrong) but would not come
> close to limiting any practical use I can imagine.
> With our architecture in Chrome, we will probably need to have some limit.
>  We haven't decided what that is yet, but since I remember others saying
> similar things when we talked about this at TPAC, it seems like it might be
> best to standardize it--even though it does feel a bit dirty.

One problem with putting a limit is that it basically forces
implementations to use a specific encoding, or pay a hefty price. For
example if we choose a 64K limit, is that of UTF8 data or of UTF16
data? If it is of UTF8 data, and the implementation uses something
else to store the date, you risk having to convert the data just to
measure the size. Possibly this would be different if we measured size
using UTF16 as javascript more or less enforces that the source string
is UTF16 which means that you can measure utf16 size on the cheap,
even if the stored data uses a different format.

/ Jonas
Received on Monday, 7 February 2011 07:39:08 GMT

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