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Apache Solr (module: core)
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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.solr.search;

import org.apache.solr.common.params.SolrParams;
import org.apache.solr.request.SolrQueryRequest;

/**
 * Create a dismax query from the input value. 

 * localParams are checked before global request params. 

 * Example: {!dismax qf='myfield mytitle^2'}foo creates a dismax query across across
 * myfield and mytitle, with a higher weight on mytitle.
 *
 * A Generic query plugin designed to be given a simple query expression from a user, which it
 * will then query against a variety of pre-configured fields, in a variety of ways, using
 * BooleanQueries, DisjunctionMaxQueries, and PhraseQueries.
 *
 * 
All of the following options may be configured for this plugin in the solrconfig as defaults,
 * and may be overridden as request parameters
 *
 * 

 *   q.alt - An alternate query to be used in cases where the main query (q) is not specified
 *       (or blank). This query should be expressed in the Standard SolrQueryParser syntax (you can
 *       use q.alt=*:* to denote that all documents should be returned when no query is
 *       specified)
 *   
tie - (Tie breaker) float value to use as tiebreaker in DisjunctionMaxQueries (should be
 *       something much less than 1)
 *   
qf - (Query Fields) fields and boosts to use when building DisjunctionMaxQueries from the
 *       users query. Format is: "fieldA^1.0 fieldB^2.2". This param can be specified
 *       multiple times, and the fields are additive.
 *   
mm - (Minimum Match) this supports a wide variety of complex expressions. read {@link
 *       org.apache.solr.util.SolrPluginUtils#setMinShouldMatch SolrPluginUtils.setMinShouldMatch}
 *       and mm expression
 *       format for details.
 *   
pf - (Phrase Fields) fields/boosts to make phrase queries out of, to boost the users query
 *       for exact matches on the specified fields. Format is: "fieldA^1.0 fieldB^2.2".
 *       This param can be specified multiple times, and the fields are additive.
 *   
ps - (Phrase Slop) amount of slop on phrase queries built for pf fields.
 *   
qs - (Query Slop) amount of slop on phrase queries explicitly specified in the "q" for qf
 *       fields.
 *   
bq - (Boost Query) a raw lucene query that will be included in the users query to influence
 *       the score. If this is a BooleanQuery with a default boost (1.0f), then the individual
 *       clauses will be added directly to the main query. Otherwise, the query will be included as
 *       is. This param can be specified multiple times, and the boosts are are additive. NOTE: the
 *       behaviour listed above is only in effect if a single bq paramter is specified.
 *       Hence you can disable it by specifying an additional, blank, bq parameter.
 *   
bf - (Boost Functions) functions (with optional boosts) that will be included in the users
 *       query to influence the score. Format is: "funcA(arg1,arg2)^1.2
 *           funcB(arg3,arg4)^2.2". NOTE: Whitespace is not allowed in the function
 *       arguments. This param can be specified multiple times, and the functions are additive.
 *   
fq - (Filter Query) a raw lucene query that can be used to restrict the super set of
 *       products we are interested in - more efficient then using bq, but doesn't influence score.
 *       This param can be specified multiple times, and the filters are additive.
 * 
 *
 * The following options are only available as request params...
 *
 * 

 *   q - (Query) the raw unparsed, unescaped, query from the user.
 *   
sort - (Order By) list of fields and direction to sort on.
 * 
 */
public class DisMaxQParserPlugin extends QParserPlugin {
  public static final String NAME = "dismax";

  @Override
  public QParser createParser(
      String qstr, SolrParams localParams, SolrParams params, SolrQueryRequest req) {
    return new DisMaxQParser(qstr, localParams, params, req);
  }
}