[XESAM] changes in the Xesam XML Query Languae

[Mikkel Kamstrup Erlandsen]

2007/5/21, jamie <jamiemcc at blueyonder.co.uk>:
>
> On Mon, 2007-05-21 at 21:43 +0200, Mikkel Kamstrup Erlandsen wrote:
>
> >
> >
> >         >
> >         > 5) And a bigger issue, that is a tough call... Should we use
> >         real dbus
> >         > objects for sessions/searches? According to Havoc Pennington
> >         it
> >         > doesn't take a roundtrip to the bus to register a new
> >         object, so
> >         > spawning lots of search objects shouldn't flood the bus (not
> >         with
> >         > object-registration requests at least).
> >
> >         yes the overhead is negligible - its not like an app is going
> >         to
> >         construct 100's of search objects all at once
> >
> > I just had seconds thoughts on this. One thing is that the spawning of
> > the Search object on the server doesn't touch the bus, but what about
> > when the client sets up a proxy to it?
> >
> > The current way where only handles are used is guaranteed to not have
> > extra dbus roundtrips and I really think this is an important
> > feature.
> >
>
> well we can - we only need a unique Id for the session so its one round
> trip max. For each new query we can append queryX where X is an
> incrementing integer to the session object path so no round trip is
> needed



This imposes additional tasks for the client. Although this could possibly
be hidden in the toolkit bindings I still think it is a bit inelegant...

Anyway it doesn't save a roundtrip in the current API. The NewSearch call
takes a query_xml that you need to pass over the bus somewhere no matter
what...

About the bus round trip; I was worried that creating the proxy search
object for the search would require a dbus round trip, are anyone certain
about this?


> Maybe we wont handle 100's of searches, but I could easily imagine
> > myself doing 50 searches/sec or whatever the engine could pull off.
> > This could fx be in a scenario where I would like to extract
> > meta-information about the index. Such as information clusters.
>
> can easily reuse existing search query objects for that - no need to
> keep creating new ones?


You can reuse the Session objects, but the Search objects are created for a
specific query. A Search is to be considered a server-side compiled
representation of a query.

Cheers,
Mikkel
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