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[IndexedDB] Handling missing/invalid values for indexes

From: Jonas Sicking <jonas@sicking.cc>
Date: Mon, 17 Oct 2011 22:02:38 -0700
Message-ID: <CA+c2ei8L_eoT87xNuQ93RR_G73eiGG8RTTsXiFgu8asK3G=AOQ@mail.gmail.com>
To: Webapps WG <public-webapps@w3.org>
Hi All,

Currently the spec is somewhat inconsistent in how it deals with
having an index on a property, and then inserting an object in an
object store which is either missing that property, or has the
property but with a value which is not a valid key.

Consider a database which has been set up as follows:

store = db.createObjectStore("mystore", { keyPath: "id" });
store.createIndex("myindex", "prop");

As the spec currently stands (and which IIRC has been implemented in
Firefox), the following behavior is defined:

store.put({ id: 1, prop: "a"}); // this will run successfully and will
insert an entry in the index with key "a"
store.put({ id: 2});  // this will run successfully and will not
insert a entry in the index
store.put({ id: 3, prop: {}); // this will throw an exception

I find this unfortunate for three reasons.

* It seems it seems inconsistent to not require that a property is
there, but that if it's there, require it to contain a "proper" value.
* It means that you can't create an index without adding constraints
on what data can be stored.
* It means creating constraints on the data without any explicit
syntax to make that clear. Compare to the 'unique' constraint which
has to be opted into using explicit syntax.

Also note that this doesn't just affect store.put and store.add calls.
It also affects what happens when you call createIndex. I.e. if you
run the put commands above first before creating the index, then that
will obviously succeed. If you then create the index as part of a
VERSION_CHANGE transaction, then the transaction will be aborted as
the index can't be created.

Here is what I propose:

I propose that we remove the requirement that we have today that if an
indexed property exists, it has to contain a valid value. Instead, if
a property doesn't contain a valid key value, we simply don't add an
entry to the index. This would of course apply both when inserting
data into a objectStore which already has indexes, as well as when
creating indexes for an object store which already contains data.

We have talked about adding a 'required' property for the options
object in the createIndex call, but haven't yet done so.  Once we do
that (if that is in v1 or v2 is a separate question), such an explicit
opt-in can require both that a property exists, and that it contains a
valid key value.

Let me know what you think.

/ Jonas
Received on Tuesday, 18 October 2011 05:03:35 UTC

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