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Date: Mon, 11 Apr 2011 18:13:16 -0700 (PDT)
From: yangyangyyy <teddyyyy123@gmail.com>
To: general@lucene.apache.org
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Subject: Re: Number of Boolean Clauses (AND vs OR)
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Thanks Doug:

when you say "executed" in parallel, could you please elaborate more on what
"execute" refers to?

I just managed to look through the code. on our Solr setup, by default, a
query "dog cat" (not phrase search) comes to a DisjunctionSumScorer, and if
by "execute" you mean the call to score(), it seems that the
DisjunctionSumScorer still evaluates score() serially, just iterating down
the multiple subscorers queue 
"scorerDocQueue", as is in 

DisjunctionSumScorer:

  protected boolean advanceAfterCurrent() throws IOException {


ConjunctionScorer looks similar , just different in the way doNext()
iterates through the doc queues.

if the above scenario is indeed run in serial, how could we enable parallel
evaluation? does that need some special config? (this is lucene 2.9.4 + Solr
1.4.2 )

Thanks a lot
Yang


###############################
On 04/11/2011 01:25 PM, entdeveloper wrote: 
> Thanks Otis. And by your answer, does this mean that individual clauses in
> a 
> boolean query are executed sequentially? not in parallel? 

Clauses are executed in parallel.  The execution of a conjunction is 
able to efficiently skip occurrences in ranges of documents that do not 
contain all clauses, while, for a disjunction, every occurrence of every 
clause must be considered. 

Doug 

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