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From Renaud Delbru <>
Subject Re: Sorting posting lists before intersection
Date Mon, 13 Oct 2008 15:52:24 GMT

Paul Elschot wrote:
> This could be done, but since not all scorers will be TermScorers it
> will be necessary to add a method to Scorer (or perhaps even to its
> DocIdSetIterator superclass):
>    public abstract int estimatedDocFreq();
> and implement this for all existing instances. TermScorer could
> implement it without estimating.
> For AND/OR/NOT such an estimation is straightforward but for
> proximity queries it would be more of a guess.
I agree. Indeed, for proximity queries, it is more tricky. Maybe taking 
the frequency of the rarest term in a PhraseQuery / SpanQuery could be a 
not so bad predictor in general.

Renaud Delbru

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