> Does it matter what order I add the sub-queries to the BooleanQuery Q. > That is, is the execution speed for the search faster (slower) if I do: > Q.add(Q1, BooleanClause.Occur.MUST); > Q.add(Q2, BooleanClause.Occur.MUST); > Q.add(Q3, BooleanClause.Occur.MUST); > As opposed to: > Q.add(Q3, BooleanClause.Occur.MUST); > Q.add(Q2, BooleanClause.Occur.MUST); > Q.add(Q1, BooleanClause.Occur.MUST); > Or does it matter at all? > > There are cases where I know that, for 99% of the time, certain portions > of my queries are likely to be more selective and I could affect the > order they get added to the BooleanQuery. Those of you who know lucene > internals, is there anything worth doing here? > Scott
I think the order in which the query is composed would not matter, as Lucene already takes care of this: the order by which the <list-of-doc-ids-of-a-term> are traversed by ConjunctionScorer (in effect for a boolean AND query) lets the more selective term lead the query execution. In fact it seems to be stronger - assume an index with 3000 docs, and a query with 3 terms: +t1 +t2 +t3 Also assume that t1, t2, t3 is more selective (rare) for docs [d0,d1000), t2 more selective for [d1000,d2000) and t3 more selective in [d2000,d3000). The way Lucene traverses these doc-ids lists, would let t1 lead the computation in the first range [0,1000], t2 lead it in the second range [1000,2000), and t3 in the 3rd range. Regards, Doron --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
