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Re: [IndexedDB] Key generation details

From: Joshua Bell <jsbell@chromium.org>
Date: Wed, 25 Jan 2012 16:45:25 -0800
Message-ID: <CAD649j6btTKxnKJvM_AwmPba08VFPyV7un3k8n=YPZmZ0j2upQ@mail.gmail.com>
To: "public-webapps@w3.org" <public-webapps@w3.org>
On Wed, Jan 25, 2012 at 3:05 PM, Israel Hilerio <israelh@microsoft.com>wrote:

> On Wednesday, January 25, 2012 12:25 PM, Jonas Sicking wrote:
> > Hi All,
> >
> > Joshua reminded me of another thing which is undefined in the
> specification,
> > which is key generation. Here's the details of how we do it in Firefox:
> >
> > The key generator for each objectStore starts at 1 and is increased by
> > 1 every time a new key is generated.
> >
> > Each objectStore has its own key generator. See comments for the
> following
> > code example:
> > store1 = db.createObjectStore("store1", { autoIncrement: true });
> > store1.put("a"); // Will get key 1
> > store2 = db.createObjectStore("store2", { autoIncrement: true });
> > store2.put("a"); // Will get key 1 store1.put("b"); // Will get key 2
> > store2.put("b"); // Will get key 2
> >
> > If an insertion fails due to constraint violations or IO error, the key
> generator
> > is not updated.
> > trans.onerror = function(e) { e.preventDefault() }; store =
> > db.createObjectStore("store1", { autoIncrement: true }); index =
> > store.createIndex("index1", "ix", { unique: true }); store.put({ ix:
> "a"}); // Will
> > get key 1 store.put({ ix: "a"}); // Will fail store.put({ ix: "b"}); //
> Will get key 2
> >
> > Removing items from an objectStore never affects the key generator.
> > Including when .clear() is called.
> > store = db.createObjectStore("store1", { autoIncrement: true });
> > store.put("a"); // Will get key 1 store.delete(1); store.put("b"); //
> Will get key
> > 2 store.clear(); store.put("c"); // Will get key 3
> > store.delete(IDBKeyRange.lowerBound(0));
> > store.put("d"); // Will get key 4
> >
> > Inserting an item with an explicit key affects the key generator if, and
> only if,
> > the key is numeric and higher than the last generated key.
> > store = db.createObjectStore("store1", { autoIncrement: true });
> > store.put("a"); // Will get key 1 store.put("b", 3); // Will use key 3
> > store.put("c"); // Will get key 4 store.put("d", -10); // Will use key
> -10
> > store.put("e"); // Will get key 5 store.put("f", 6.00001); // Will use
> key 6.0001
> > store.put("g"); // Will get key 7 store.put("f", 8.9999); // Will use
> key 8.9999
> > store.put("g"); // Will get key 9 store.put("h", "foo"); // Will use key
> "foo"
> > store.put("i"); // Will get key 10
> > store.put("j", [1000]); // Will use key [1000] store.put("k"); // Will
> get key 11
> > // All of these would behave the same if the objectStore used a keyPath
> and
> > the explicit key was passed inline in the object
> >
> > Aborting a transaction rolls back any increases to the key generator
> which
> > happened during the transaction. This is to make all rollbacks consistent
> > since rollbacks that happen due to crash never has a chance to commit the
> > increased key generator value.
> > db.createObjectStore("store", { autoIncrement: true }); ...
> > trans1 = db.transaction(["store"]);
> > store_t1 = trans1.objectStore("store");
> > store_t1.put("a"); // Will get key 1
> > store_t1.put("b"); // Will get key 2
> > trans1.abort();
> > trans2 = db.transaction(["store"]);
> > store_t2 = trans2.objectStore("store");
> > store_t2.put("c"); // Will get key 1
> > store_t2.put("d"); // Will get key 2
> >
> > / Jonas
> >
>
> IE follows the same behavior, as FF, for all of these scenarios.
>
> Israel
>
>
> This is the behavior I'd expect, but it looks like Chromium currently
deviates from this in a few cases. I'll dig in further to see if the issue
is in Chromium or my test code.
Received on Thursday, 26 January 2012 00:45:52 GMT

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