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https://issues.apache.org/jira/browse/LUCENE-4378?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13453640#comment-13453640
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Hoss Man commented on LUCENE-4378:
----------------------------------
bq. In my opinion, a better approach is something like the BoostingQuery in
lucene/queries for this demoting of terms.
My confusion is that your argument seems like it confluates the concept/syntax
with an implementation -- you're saying you don't like a particular
implementation, therefore you don't think QueryParser should allow for the
concept.
I'm suggesting we let the syntax in the grammer allow for the concept of
negative boosts, and then let the implementations of QueryParser decide what it
means -- the default implementation could be "error". Some users could choose
to have a subclass with "simple" implementation (literally using the negative
boost on the query) if it makes sense for them, and other users could do other
things.
For example: suppose i wanted to use BoostingQuery like you suggest, but i want
to be able to use it in some way with the QueryParser syntax. If the grammer
_allowed_ for "foo bar^-100" to do *something* then by subclassing the
QueryParser i could impelement demoting items using this syntax with something
like...
{noformat}
public MyParser extends QueryParser {
@Override
public BooleanQuery getBooleanQuery(List<BooleanClause> clauses,
boolean disableCoord) throws ParseException {
BooleanQuery q = super.getBooleanQuery(clauses, disableCoord);
Query result = q;
for (clause : q.getClauses(){
if (clause.getBoose() < 0) {
q.removeClause(clause);
penalty = -1/clause.getBoost();
clause.setBoost(1);
result = new BoostingQuery(result, clause, penalty)
}
return result;
}
@Override
public void checkBoost(Query q, float boost) {
// override super which will throw an exception if boost is negative
// :NOOP:
}
}
{noformat}
> QueryParsers do not support negative boosts
> -------------------------------------------
>
> Key: LUCENE-4378
> URL: https://issues.apache.org/jira/browse/LUCENE-4378
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Hoss Man
> Attachments: LUCENE-4378-test.patch
>
>
> Negative query boosts have been supported at the "Query" object level for a
> long time (resulting in negative scores for matching documents), but
> evidently we never updated the QueryParsers to know about this - attempting
> to specify a negative boost in the query string results in a parse error.
> we should probably add this to the parser grammer(s)
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