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Re: [selectors-api] Summary of Feature Requests for v2

From: Boris Zbarsky <bzbarsky@MIT.EDU>
Date: Thu, 24 Sep 2009 09:06:55 -0400
Message-ID: <4ABB6EEF.2050802@mit.edu>
To: Sean Hogan <shogun70@westnet.com.au>
CC: public-webapps <public-webapps@w3.org>
On 9/24/09 6:29 AM, Sean Hogan wrote:
> I would be surprised if an implementation didn't create an internal
> lookup table keyed off the selector text.

Gecko doesn't.  Webkit doesn't.

I just checked really quickly, and on my machine (a year-plus old 
laptop) parsing the ".foo .bar .baz" selector and destroying the 
selector object before returning in Gecko takes about 80% of the 
"overhead" (that is, not walking the tree and doing selector matching) 
time of a querySelector() call.  Or, in numbers, about 5.5us per call. 
Webkit's time for executing my testcase is comparable, though I can't 
tell how much of their time is selector parsing.

If you're doing less than 1,000 calls that involve selectors api per 
second, the selector-parsing time is probably not that relevant.  But I 
don't know what the use cases are here.

-Boris
Received on Thursday, 24 September 2009 13:07:41 GMT

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