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Re: [Bug 11257] New: Should IDBCursor.update be able to create a new entry?

From: Jonas Sicking <jonas@sicking.cc>
Date: Fri, 12 Nov 2010 11:11:20 -0800
Message-ID: <AANLkTikoYT9MbuD5UK1Ke6o0og1yekbVVr2XzBQ278ju@mail.gmail.com>
To: Jeremy Orlow <jorlow@chromium.org>
Cc: public-webapps@w3.org
On Fri, Nov 12, 2010 at 12:33 AM, Jeremy Orlow <jorlow@chromium.org> wrote:
> On Fri, Nov 12, 2010 at 9:26 AM, Jonas Sicking <jonas@sicking.cc> wrote:
>>
>> On Thu, Nov 11, 2010 at 9:12 PM, Jeremy Orlow <jorlow@chromium.org> wrote:
>> > On Fri, Nov 12, 2010 at 12:11 AM, Jonas Sicking <jonas@sicking.cc>
>> > wrote:
>> >>
>> >> On Thu, Nov 11, 2010 at 11:51 AM, Jeremy Orlow <jorlow@chromium.org>
>> >> wrote:
>> >> > On Thu, Nov 11, 2010 at 8:46 PM, Jonas Sicking <jonas@sicking.cc>
>> >> > wrote:
>> >> >>
>> >> >> On Thu, Nov 11, 2010 at 5:11 AM, Jeremy Orlow <jorlow@chromium.org>
>> >> >> wrote:
>> >> >> > On Mon, Nov 8, 2010 at 2:12 PM, <bugzilla@jessica.w3.org> wrote:
>> >> >> >>
>> >> >> >> http://www.w3.org/Bugs/Public/show_bug.cgi?id=11257
>> >> >> >>
>> >> >> >>           Summary: Should IDBCursor.update be able to create a
>> >> >> >> new
>> >> >> >> entry?
>> >> >> >>           Product: WebAppsWG
>> >> >> >>           Version: unspecified
>> >> >> >>          Platform: PC
>> >> >> >>        OS/Version: All
>> >> >> >>            Status: NEW
>> >> >> >>          Severity: normal
>> >> >> >>          Priority: P2
>> >> >> >>         Component: Indexed Database API
>> >> >> >>        AssignedTo: dave.null@w3.org
>> >> >> >>        ReportedBy: jonas@sicking.cc
>> >> >> >>         QAContact: member-webapi-cvs@w3.org
>> >> >> >>                CC: mike@w3.org, public-webapps@w3.org
>> >> >> >>
>> >> >> >>
>> >> >> >> What should happen in the following case:
>> >> >> >>
>> >> >> >> db.transaction(["foo"]).objectStore("foo").openCursor().onsuccess
>> >> >> >> =
>> >> >> >> function(e)
>> >> >> >> {
>> >> >> >>  var cursor = e.result;
>> >> >> >>  if (!cursor)
>> >> >> >>    return;
>> >> >> >>
>> >> >> >>  cursor.delete();
>> >> >> >>  cursor.update({ id: 1234, value: "Benny" });
>> >> >> >> }
>> >> >> >>
>> >> >> >>
>> >> >> >> This situation can of course arrive in more subtle ways:
>> >> >> >>
>> >> >> >> os = db.transaction(["foo"]).objectStore("foo");
>> >> >> >> os.openCursor().onsuccess = function(e) {
>> >> >> >>  var cursor = e.result;
>> >> >> >>  if (!cursor)
>> >> >> >>    return;
>> >> >> >>
>> >> >> >>  cursor.update({ id: 1234, value: "Benny" });
>> >> >> >> }
>> >> >> >> os.delete(1234);
>> >> >> >>
>> >> >> >>
>> >> >> >> As specified, IDBCursor.update behaves just like
>> >> >> >> IDBObjectStore.put
>> >> >> >> and
>> >> >> >> just
>> >> >> >> creates a new entry, but this might be somewhat unexpected
>> >> >> >> behavior.
>> >> >> >
>> >> >> > Let's just remove update and delete from IDBCursor and be done
>> >> >> > with
>> >> >> > it.
>> >> >>
>> >> >> The problem is that you can't always get to the key of the
>> >> >> objectStore
>> >> >> entry to delete/update. Specifically if the objectStore uses
>> >> >> out-of-line keys the cursor doesn't expose those.
>> >> >
>> >> > Why not fix this use case then?  I.e. change the cursor to return
>> >> > .indexKey,
>> >> > .primaryKey, .value (or something like that).  If we did this, we
>> >> > could
>> >> > even
>> >> > get rid of the different between object cursors and key cursors
>> >> > (which
>> >> > overload the .value to mean the primary key, which is quite
>> >> > confusing).
>> >>
>> >> I would be ok with exposing some new property which exposes the
>> >> objectstore key.
>> >
>> > And thus get rid of the openKeyCursor and getKey?  This would make the
>> > spec
>> > a bit more complicated (we'd need to have 2 IDBCursor objects, one
>> > that inherits from the other), but seems much simpler to use.  Shall I
>> > file
>> > a bug?
>>
>> I think openKeyCursor is still needed. There are performance
>> advantages since you save a btree lookup for each iterated entry, and
>> you also don't need to spend time reading and possibly deserializing a
>> potentially large object if all that's needed, for example when doing
>> a join, is the key.
>>
>> All I was suggesting is that we have
>>
>> interface IDBCursor {
>>  ...
>>  readonly attribute any objectStoreKey;
>>  readonly attribute any key;
>>  readonly attribute any value;
>>  ...
>> }
>>
>> When using a cursor from IDBIndex.openCursor() all three properties
>> are set. When using a cursor from IDBIndex.openKeyCursor() only
>> objectStoreKey and key are set. When using a cursor from
>> IDBObjectStore.openCursor() key and value are set and either we make
>> objectStoreKey "undefined" or return the same thing as key.
>>
>> Or, we make IDBObjectStore.openCursor() return a cursor which doesn't
>> have a objectStoreKey property.
>
> Either way is fine with me.  I think the latter is probably slightly better
> and worth the extra implementation hassle.

Same for me. What do others think?

/ Jonas
Received on Friday, 12 November 2010 19:12:14 GMT

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