> Yes. In a constructor function, the hidden class begins with an
> element that also includes a prototype. In two different constructor
> functions these initial elements will be different, making their
> hidden classes different.
Does this mean that if I make sure that both the mongo driver and my code
uses the literal empty object {} for creating new objects they will share
the same root class?
On Friday, July 20, 2012 2:21:39 AM UTC-3, jMerliN wrote:
>
> Hi Sebastian,
>
> > It is my understanding that hidden classes are not shared between
> different
> > constructors, even if I construct structurally identical objects with
> the
> > same properties and in the same order. This seems to imply that
> > deserialized objects coming from mongodb will not share the same hidden
> > class as structurally identical objects created by the constructors,
> hence
> > functions that use these objects will not be well optimized into native
> > code. Am I right?
>
> Yes. In a constructor function, the hidden class begins with an
> element that also includes a prototype. In two different constructor
> functions these initial elements will be different, making their
> hidden classes different.
>
> If you have hot code that is being impacted because you pass it both
> objects you construct and ones from the MongoDB driver you're using,
> one thing you can do is make your constructor take the MongoDB object
> representation as an input. Then you would be able to make your hot
> code monomorphic. If you don't have any hot code being impacted, it's
> probably not something you should worry about unless your Mongo driver
> is putting objects it constructs into dictionary mode for some reason.
>
> An example: http://jsfiddle.net/xznxP/
>
> "hot" only deoptimizes when given the raw object here, which has a
> different hidden class.
>
> > Is there any hidden class inheritance built into v8? That is, if I
> create
> > object o={a:1, b:2} and later add o.z=3, will native code optimized for
> the
> > hidden class before the property-add still work unmodified afterwards?
>
> No.
>
> - Justin
>
> On Jul 19, 4:16 pm, Sebastian Ferreyra Pons <[email protected]>
> wrote:
> > I have two questions.
> >
> > #1
> > I'm developing a Node.js/Mongodb web app.
> >
> > This means that objects used in the code will be created by at least two
> > different code paths:
> >
> > 1. Constructor functions
> > 2. Deserialization code in the mongo driver.
> >
> > It is my understanding that hidden classes are not shared between
> different
> > constructors, even if I construct structurally identical objects with
> the
> > same properties and in the same order. This seems to imply that
> > deserialized objects coming from mongodb will not share the same hidden
> > class as structurally identical objects created by the constructors,
> hence
> > functions that use these objects will not be well optimized into native
> > code. Am I right?
> >
> > #2
> > Is there any hidden class inheritance built into v8? That is, if I
> create
> > object o={a:1, b:2} and later add o.z=3, will native code optimized for
> the
> > hidden class before the property-add still work unmodified afterwards?
>
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