On Jan 26, 2010, at 11:13 AM, has wrote:
The Apple Event Object Model was optimized for System 7, where IPC
was extremely expensive
I know; I was on the AppleEvents engineering team at the time :)
IPC is still extremely expensive, by the way, although not quite as
much so. The actual OS-level process switch is faster, but there is
still a lot of work involved in marshalling and unmarshalling data.
so generally works best if you can use a few complex commands rather
than lots of simple commands.
Agreed. The problem is that iTunes doesn't implement the complex
commands well. A lot of them either fail, or are implemented using
linear search instead of querying the database.
For example, you can't get properties of multiple items:
album of every track of every playlist whose artist is "The Beatles"
fails with error "Handler only handles single objects". Instead you
have to remove the "album of" part, get back a list of object
specifiers, and loop over them getting the album names. Which of
course involves lots of IPC calls.
There are other cases of 'whose' queries that take extremely long to
run, depending on the size of your library, because they do a linear
search. Try this:
id of every track whose played count is 1234
On my 2.4GHz MacBook Pro this takes 15 seconds to run, with iTunes
consuming 100% CPU. (I do have 10,000 tracks in my library.) By
comparison, creating a smart playlist in iTunes with the same criteria
is instantaneous.
—Jens_______________________________________________
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