Chris Hostetter wrote:
: > so do you convert A ! B ! C into a three clause boolean query, or a two
: > clause BooleanQuery that contains another two clause BooleanQuery?
: >
: It becomes a three clause boolean query...would there be a difference in
: scoring? I assumed not and it used to make a boolean that contained
: another boolean...these days it checks to see if its in a chain of the
: same operator and makes only one boolean.
there is in fact a difference in score ... a big difference depending
on how the coordFactor comes into play. your three-clause approach makes
sense to me as the "right" approach, but your "in a chain of the same
operator" comment scares me ... how does "A | B | C ! D ! E" get parsed?
I would assume it should result in the QueryParser equivilent of
"A B C -D -E" ... is there any way to produce a the same underlying
BooleanQuery using your syntax?
This exchange has caused me to reassess my syntax. It seems that
QueryParser's handling of A B C -D -E is special because QueryParser
does not have any operator precedence rules (unless the 1 rule is that
all operators resolve with the same precedence <g>). What would appear
in my parser to map to A B C -D -E i.e. A | B | C ! D ! E, actually
maps to: A B (+C -D -E). If you want precedence applied to your query,
there is no way around this-- that is what operator precedence creates.
Unfortunately, that means my parser is not quite as "rich" as
QueryParser. While I can duplicate the same hits, QueryParser has a
greater scoring expressiveness (QueryParser can express precedence
queries, but you must use parenthesis). My current idea (and mostly
implemented) is to add a set of operators to my syntax that force a
first level precedence resolve. To express the query A B C -D -E you
would use A || B || C !! D !! E . Doubling the operator would
effectively make the operator bind at the level of parenthesis. You
could then mix like this: A B ! C & A || Z || B !! H & Q.
I think that this change will be a large step forward in supporting the
entire Lucene Query/Scoring language with my parser.
- Mark
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