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Re: [Bug 11270] New: Interaction between in-line keys and key generators

From: Keean Schupke <keean@fry-it.com>
Date: Thu, 11 Nov 2010 12:48:55 +0000
Message-ID: <AANLkTi=x2S1pjTWQoGzG95+JL5SYNrb4+fTY=+JkAcP0@mail.gmail.com>
To: Jeremy Orlow <jorlow@chromium.org>
Cc: Jonas Sicking <jonas@sicking.cc>, "Tab Atkins Jr." <jackalmage@gmail.com>, Pablo Castro <Pablo.Castro@microsoft.com>, "bugzilla@jessica.w3.org" <bugzilla@jessica.w3.org>, "public-webapps@w3.org" <public-webapps@w3.org>
Integers can be big 8bytes is common. It is generally assumed that the
auto-increment counter will be big enough, overflow would wrap, and if the
ID already exists there would be an error. In my experience auto-increment
columns must be integers.

Cheers,
Keean.

On 11 November 2010 12:20, Jeremy Orlow <jorlow@chromium.org> wrote:

> On Thu, Nov 11, 2010 at 2:37 AM, Jonas Sicking <jonas@sicking.cc> wrote:
>
>> On Wed, Nov 10, 2010 at 3:15 PM, Tab Atkins Jr. <jackalmage@gmail.com>
>> wrote:
>> > On Wed, Nov 10, 2010 at 2:07 PM, Jonas Sicking <jonas@sicking.cc>
>> wrote:
>> >> On Wed, Nov 10, 2010 at 1:50 PM, Tab Atkins Jr. <jackalmage@gmail.com>
>> wrote:
>> >>> On Wed, Nov 10, 2010 at 1:43 PM, Pablo Castro
>> >>> <Pablo.Castro@microsoft.com> wrote:
>> >>>>
>> >>>> From: public-webapps-request@w3.org [mailto:
>> public-webapps-request@w3.org] On Behalf Of bugzilla@jessica.w3.org
>> >>>> Sent: Monday, November 08, 2010 5:07 PM
>> >>>>
>> >>>>>> So what happens if trying save in an object store which has the
>> following
>> >>>>>> keypath, the following value. (The generated key is 4):
>> >>>>>>
>> >>>>>> "foo.bar"
>> >>>>>> { foo: {} }
>> >>>>>>
>> >>>>>> Here the resulting object is clearly { foo: { bar: 4 } }
>> >>>>>>
>> >>>>>> But what about
>> >>>>>>
>> >>>>>> "foo.bar"
>> >>>>>> { foo: { bar: 10 } }
>> >>>>>>
>> >>>>>> Does this use the value 10 rather than generate a new key, does it
>> throw an
>> >>>>>> exception or does it store the value { foo: { bar: 4 } }?
>> >>>>
>> >>>> I suspect that all options are somewhat arbitrary here. I'll just
>> propose that we error out to ensure that nobody has the wrong expectations
>> about the implementation preserving the initial value. I would be open to
>> other options except silently overwriting the initial value with a generated
>> one, as that's likely to confuse folks.
>> >>>
>> >>> It's relatively common for me to need to supply a manual value for an
>> >>> id field that's automatically generated when working with databases,
>> >>> and I don't see any particular reason that my situation would change
>> >>> if using IndexedDB.  So I think that a manually-supplied key should be
>> >>> kept.
>> >>
>> >> I'm fine with either solution here. My database experience is too weak
>> >> to have strong opinions on this matter.
>> >>
>> >> What do databases usually do with columns that use autoincrement but a
>> >> value is still supplied? My recollection is that that is generally
>> >> allowed?
>> >
>> > I can only speak from my experience with mySQL, which is generally
>> > very permissive, but which has very sensible behavior here imo.
>> >
>> > You are allowed to insert values manually into an AUTO_INCREMENT
>> > column.  The supplied value is stored as normal.  If the value was
>> > larger than the current autoincrement value, the value is increased so
>> > that the next auto-numbered row will have an id one higher than the
>> > row you just inserted.
>> >
>> > That is, given the following inserts:
>> >
>> > insert row(val) values (1);
>> > insert row(id,val) values (5,2);
>> > insert row(val) values (3);
>> >
>> > The table will contain [{id:1, val:1}, {id:5, val:2}, {id:6, val:3}].
>> >
>> > If you have uniqueness constraints on the field, of course, those are
>> > also used.  Basically, AUTO_INCREMENT just alters your INSERT before
>> > it hits the db if there's a missing value; otherwise the query is
>> > treated exactly as normal.
>>
>> This is how sqlite works too. It'd be great if we could make this
>> required behavior.
>>
>
> What would we do if what they provided was not an integer?  What happens if
> the number they insert is so big that the next one causes overflow?  What is
> the use case for this?  Do we really think that most of the time users do
> this it'll be intentional and not just a mistake?
>
> J
>
Received on Thursday, 11 November 2010 12:49:28 GMT

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