Grant Ingersoll wrote:
On Oct 19, 2008, at 7:08 PM, Michael Busch wrote:
Grant Ingersoll wrote:
On Oct 19, 2008, at 12:56 AM, Mark Miller wrote:
Grant Ingersoll wrote:
Bear with me, b/c I'm not sure I'm following, but looking at
https://issues.apache.org/jira/browse/LUCENE-1422, I see at least
5 different implemented Attributes.
So, let's say I add a 5 more attributes and now have a total of 10
attributes. Are you saying that I then would have, potentially, 10
different variables that all point to the token as in the code
snippet above where the casting takes place? Or would I just
create a single "Super" attribute that folds in all of my new
attributes, plus any other existing ones? Or, maybe, what I would
do is create the 5 new attributes and then 1 new attribute that
extends all 10, thus allowing me to use them individually, but
saving me from having to do a whole ton of casting in my Consumer.
Potentially one consumer doing 10 things, but not likely right? I
mean, things will stay logical as they are now, and rather than a
super consumer doing everything, we will still have a chain of
consumers each doing its own piece. So more likely, maybe something
comes along every so often (another 5, over *much* time, say) and
each time we add a Consumer that uses one or two TokenStream types.
And then its just an implementation detail on whether you make a
composite TokenStream - if you have added 10 new attributes and see
it fit to make one consumer use them all, sure, make a composite,
super type, but in my mind, the way its done in the example code is
clearer/cleaner for a handful of TokenStream types. And even if you
do make the composite,super type, its likely to just be a sugar
wrapper anyway - the implementation for say, payload and positions,
should probably be maintained in their own classes anyway.
Well, there are 5 different attributes already, all of which are
commonly used. Seems weird to have to cast the same var 5 different
ways. Definitely agree that one would likely deal with this by
wrapping, but then you end up either needing to extend your wrapper
or add new wrappers...
Well yes, there are 5 attributes, but n neither of the core
tokenstreams and -filters that I changed in my patch did I have to
use more than two or three of those. Currently the only attributes
that are really used are PositionIncrementAttribute and
PayloadAttribute. And the OffsetAttribute when TermVectors are turned
on.
Even in the indexing chain currently we don't have a single consumer
that needs all attributes. The FreqProxWriter needs positions and
payloads, the TermVectorsWriter needs positions and offsets.
I have an application that uses all the attributes of a Token, or at
least, almost all of them. There are many uses for Lucene's analysis
code that have nothing to do with indexing, Consumers or even Lucene.
Also, you don't have to cast the same variable multiple times. In the
current patch you would call e. g.
token.getAttribute(PayloadAttribute.class) and keep a reference to it
in the consumer or filter.
IMO even calling getAttribute() 5 times or so and storing the
references wouldn't be so bad. And if you really don't like it you
could make a wrapper as you said. You also mentioned the
disadvantages of the wrapper, e. g. that you would have to extend it
to add new attributes. But then, isn't that the same disadvantage the
current Token API has?
True. I didn't say the idea was bad, in fact I mostly like it, I was
just saying I'd like to explore how it would work in practice and the
main thing that struck me was all the casting or all the references.
Since it's likely that you only deal with a Token one at a time,
you're right, it's probably not a big deal other than the code looks
funny, IMO.
You could even use the new API in exact the same way as the old one.
Just create a subclass of Token that has all members you need and
don't add any attributes.
So I think the new API adds more flexibility, and still offers to use
it in the same way as the old one. I however think the recommended
best practice should be to use the new attributes, for reusability of
consumers that only need certain attributes.
Perhaps it would be useful for Lucene to offer exactly one subclass of
Token that we guarantee will always have all known Attributes (i.e.
the ones Lucene provides) available to it for casting purposes.
Yeah we could do that. In fact, I did exactly this when I started
working on this patch. I created a class called PlainToken, which had
all the termBuffer and attributes logic, and changed Token to extend it.
Then the new getToken() method would return an instance of PlainToken.
My main concern with this approach is that it will make the code in the
indexer more complicated, because it always has to check if we have a
Token or PlainToken; if it's a Token then it has to use the get*()
method directly, for a PlainToken it has tocheck for the *Attributes. So
that's a bit messy (it's in fact exactly like that in the current patch
for backwards-compatibility, but we could clean this up in 3.0). So for
code simplicity I'm slightly in favor of not creating the a class that
implements a default set of functionality without Attributes.
-Michael
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