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Date: Thu, 6 Mar 2008 17:34:52 +0800
From: "Eric Th" <blueye117@gmail.com>
To: java-user@lucene.apache.org
Subject: Re: Boolean Query search performance
In-Reply-To: <Pine.LNX.4.62.0803052039210.20795@radix.cryptio.net>
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2008/3/6, Chris Hostetter <hossman_lucene@fucit.org>:
>
>
> : If I do a query.toString(), both queries give different results, which
>
> : is probably a clue (additional paren's with the BooleanQuery)
> :
> : Query.toString the old way using queryParser:
> :     +(id:1^2.0 id:2 ... ) +type:CORE
> :
> : Query.toString the new way using BooleanQuery:
> :     +((id:1^2.0) (id:2) ... ) +type:CORE
>
>
> i didn't look too closely at the psuedo code you posted, but the
> additional parens normally indicates that you are actually creating an
> extra layer of BooleanQueries (ie: a BooleanQuery with only one clause for
> each term) ... but the rewrite method should optimize those away (even
> back in lucene 2.2) ... if you look at query.rewrite(reader).toString()
> then the queries *really* should be the same, if they aren't, then that
> may be your culprit.


look here,
parens will also be add is each term has a boost value larger than 1.0.

public String toString(String field) {
    StringBuffer buffer = new StringBuffer();
    boolean needParens=(getBoost() != 1.0) ||
(getMinimumNumberShouldMatch()>0) ;
    if (needParens) {
      buffer.append("(");
    }

    for (int i = 0 ; i < clauses.size(); i++) {
      BooleanClause c = (BooleanClause)clauses.get(i);
      if (c.isProhibited())
        buffer.append("-");
      else if (c.isRequired())
        buffer.append("+");

      Query subQuery = c.getQuery();
      if (subQuery instanceof BooleanQuery) {      // wrap sub-bools in
parens
        buffer.append("(");
        buffer.append(c.getQuery().toString(field));
        buffer.append(")");
      } else
        buffer.append(c.getQuery().toString(field));

      if (i != clauses.size()-1)
        buffer.append(" ");
    }

    if (needParens) {
      buffer.append(")");
    }

    if (getMinimumNumberShouldMatch()>0) {
      buffer.append('~');
      buffer.append(getMinimumNumberShouldMatch());
    }

    if (getBoost() != 1.0f)
    {
      buffer.append(ToStringUtils.boost(getBoost()));
    }

    return buffer.toString();
  }


-Hoss


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