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RE: [indexeddb] Count property on IDBCursor

From: Eliot Graff <Eliot.Graff@microsoft.com>
Date: Mon, 11 Jul 2011 21:29:56 +0000
To: Jonas Sicking <jonas@sicking.cc>, Israel Hilerio <israelh@microsoft.com>
CC: "public-webapps@w3.org" <public-webapps@w3.org>
Message-ID: <CE3A5BFD1228D84A8D9C158EEC195FD53CC9C9A6@TK5EX14MBXW601.wingroup.windeploy.ntdev.microsoft.com>
Added count() to IDBIndex, IDBIndexSync, IDBObjectStore, and IDBObjectStoreSync. Updated the editor's draft.

Let me know if any changes are required.

Thanks,

E

> -----Original Message-----
> From: public-webapps-request@w3.org [mailto:public-webapps-
> request@w3.org] On Behalf Of Jonas Sicking
> Sent: Tuesday, June 28, 2011 12:50 PM
> To: Israel Hilerio
> Cc: public-webapps@w3.org
> Subject: Re: [indexeddb] Count property on IDBCursor
> 
> On Mon, Jun 27, 2011 at 10:42 AM, Israel Hilerio <israelh@microsoft.com>
> wrote:
> > On Thursday, June 23, 2011 7:42 PM, Jonas Sicking wrote:
> >> On Thu, Jun 23, 2011 at 5:34 PM, Israel Hilerio
> >> <israelh@microsoft.com>
> >> wrote:
> >> > Is there a reason why we don't have a count or number of records
> >> > property on IDBCursor?  Pablo told me that we used to have one.
> >> > What
> >> happened to it?
> >> > It will be great to bring it back.
> >>
> >> The problem is that counting the number of records in a given range
> >> can be a very expensive operation. There are various database
> >> implementations out there that lets you get an approximate count for
> >> a given key range, but that isn't good enough if since we want
> interoperability across implementations.
> >>
> >> Since getting an exact count is a pretty expensive operation
> >> generally, we don't want to force implementations to always calculate
> >> the count every time a cursor is created. Hence getting the count
> >> would have to be an asynchronous operation, which would look pretty
> >> awkward as an API on the cursor object I think.
> >>
> >> What could possibly make more sense is to add
> >>
> >> IDBRequest count(in IDBKeyRange range)
> >>
> >> on IDBObjectStore and IDBIndex. My main concern with that is that
> >> while that seems like a pretty cheap operation, in the order of
> >> get(), it might be as slow as creating a cursor and iterating each
> >> entry while increasing a counter (minus the overhead of crossing
> >> between C++ and JS for every callback). But maybe that's ok.
> >>
> >> / Jonas
> >
> > I understand where you're coming from regarding performance.  I like your
> idea of adding a count method to the IDBObjectStore and IDBIndex.  This will
> deal with the scenarios we're thinking about.  Do you want to add this to the
> spec or want us to do that?
> 
> Would be great if you could add this. Please do make the function able to
> take both a IDBKeyRange or a value, like .get() and .delete() does.
> 
> / Jonas
> 
Received on Monday, 11 July 2011 21:30:25 GMT

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