Erik Hatcher writes:
> > Your changes look great in general, though I find some issues:
> > 1) 'stop OR stop AND stop' where stop is a stopword gives a parse
> > error:
> > Encountered "<EOF>" at line 1, column 0.
> > Was expecting one of:
> > <NOT> ...
> > ...
> I think you must have tried this in a transient state when I forgot to
> check in some JavaCC generated files. Try again. This one now returns
> an empty BooleanQuery.
I'm a bit puzzled, since I called javacc myself, so generated files should
not matter, but if it's fixed, I don't care about what went wrong.
> > 2) Single term queries using +/- flags are parse to a query without
> > flag
> > +a -> a
> Hmmm.... this is a debatable one. It's returning a TermQuery in this
> case for "a". Is that appropriate? Or should it return a BooleanQuery
> with a single TermQuery as required?
I'd prefer, if query parser parses queries created by query.toString()
to the same query. But that's just a nice to have.
> I think having it optimized to a TermQuery makes the most sense.
> Though, putting it in a BooleanQuery does make this next one simpler...
> > -a -> a
> > While this doesn't make a difference for +a it's a bit strange for -a,
> > OTOH -a isn't a usable query anyway.
> Oops... yeah, you're right. If its a single clause right now it
> doesn't wrap in a BooleanQuery and thus does not take into account the
> modifier +/-/NOT. But as you say, this is a bogus query anyway. I
> guess the right thing to do is wrap both the +a query as above and the
> -a query into a BooleanQuery with the modifier set appropriately.
The question how to handle BooleanQueries, that contain prohibited terms
only, is a question on it's own.
In my fix I choose to silently drop these queries. Basically because it's
effectivly dropped during querying anyway.
In an application, I handled this by dropping the query and notifying the
user, that some part of the query could not be handled and was ignored.
> > 3) a OR NOT b parses to 'a -b' which is the same as 'a AND NOT b'
> > IMHO `a OR NOT b' should be `a OR (NOT b)' though lucene cannot
> > search
> > that. Maybe it should raise an error...
> Actually it parses like this:
> a OR NOT b -> a -b
> a AND NOT b -> +a -b
> So they are slightly different, though the effect will be the same.
> > a OR NOT b AND c (parsed to a -(+b +c)) should IMHO be parsed to `a
> > (-b +c)'
> Ah, ok.... so NOT gets much higher precedence than I'm currently giving
> it. That might take me a while to achieve, but I'll give it a shot.