Indexing yields a performance improvement in some stylesheets, by reducing
the amount of tree-walking needed to find elements by name. But it does
have some computational/storage cost, and some stylesheets won't benefit
from it. As with any optimization, we're playing the odds...
Internally, indexing can be turned on or off when the DTM is requested
from the DTMManager -- we don't attempt to index RTFs, for example, since
they're usually small enough (and transient enough) that the cost of
indexing would outweigh the gain. But I don't think we've exposed any way
to control that via the user APIs; it appears to be hardcoded in the
Transformer.transform() call.
If you want to experiment with it and see whether exposing this control
would be useful, the patch point is in the Transformer.transform() method,
where it calls
DTM dtm = mgr.getDTM(source, false, this, true, true);
Changing that to
DTM dtm = mgr.getDTM(source, false, this, true, false);
would turn off indexing.
If that does turn out to be significantly helpful for a significant number
of stylesheets, we should probably post an Enhancement request in
Bugzilla suggesting that a feature be created to control this.
______________________________________
Joe Kesselman / IBM Research
