Solr利用Lucene提供查询解析和搜索服务，内置多种QParser，但有时需自定义以满足特定需求。本文介绍了如何创建QParserPlugin，实现对用户搜索词的扩展和同义词处理，通过配置requestHandler和编写QParser代码，实现低级查询解析功能。
Solr基于Lucene提供了方便的查询解析和搜索服务器的功能，可以以插件的方式集成，非常容易的扩展我们自己需要的查询解析方式。其中，Solr内置了一些QParser，对一些没有特殊要求的应用来说，可以直接使用这些查询解析组件，而无需做任何修改，只需要了解这些查询解析组件提供的基本参数（Local Params），就可以实现强大的搜索功能。
对于Solr来说，它的设计目标就是尽可能屏蔽底层Lucene的复杂度和难点，而是通过提供可配置的方式来实现全文检索。我们标题所说的Low Level是指，在Solr里面直接使用Lucene的查询语法，来构造满足需要的查询，例如：+(title:solr) +(+(title:lucene content:hadoop) (title:search))，这样的话，你应该了解Lucene的查询语法。因为在实际应用中，完全使用Solr自带一些QParser可能不能够达到我们的目的，比如，你在对数据进行索引，索引时使用了词典的方式进行分词，词典中出现的一些关键词很可能是与用户交互设计中内容相关的（如搜索某个关键词，向用户推荐一些向关键词），那么，在前端需要将某些关键词进行某种组合，提交到后端进行解析搜索。在后端，就会存在一个专门的查询解析组件（在Solr中成为QParser，可以扩展），最终将解析成Lucene识别的“语言”，从而进行索引搜索，返回搜索结果。
下面是一个简单的例子：
用户搜索“北京”，我需要提供相关的一组同义关键词：“北平”、”首都“、”京城“、”京都“；而此时，与”北京“相关的一组关键词：”首都博物馆“、”故宫“、”天坛“、”八达岭长城“，其中”首博“是”首都博物馆“的同义词；我们需要实现的是，当用户搜索”北京“时，对其进行同义词扩展搜索（这个在Solr里面可以直接使用同义词Analyzer），但是当用户点击这组相关关键词时，需要进行扩展，比如点击”首都博物馆“进行搜索，这时扩展搜索Lucene能够解析的形式为：
+((title:北京 content:北京) (title:北平 content:北平) (title:首都 content:首都) (title:京城 content:京城) (title:京都 content:京都)) +((title:首都博物馆 content:首都博物馆) (title:首博 content:首博))当然，Solr提供了一个QParserPlugin插件，核心查询解析在LuceneQParser中实现，是一个相对Low Level的组件，只需要在solrconfig.xml中配置好相应的requestHandler即可，实例如下：
<queryParser name="lucene" class="org.apache.solr.search.LuceneQParserPlugin"/>
<requestHandler name="/lucene" class="solr.SearchHandler">
<lst name="defaults">
<str name="defType">lucene</str>
<str name="bf">recip(ms(NOW,publishDate),3.16e-13,1,1)</str>
<str name="qf">title^1.50 content</str>
<bool name="hl">true</bool>
<str name="hl.fl">title content</str>
<int name="hl.fragsize">100</int>
<int name="hl.snippets">3</int>
<str name="fl">*,score</str>
<str name="qt">standard</str>
<str name="wt">standard</str>
<str name="version">2.2</str>
<str name="echoParams">explicit</str>
<str name="indent">true</str>
<str name="debugQuery">on</str>
<str name="explainOther">on</str>
</lst>
</requestHandler>http://192.168.0.181:8080/solr/core3/lucene/?q=+((title:北京 content:北京) (title:北平 content:北平) (title:首都 content:首都) (title:京城 content:京城) (title:京都 content:京都)) +((title:首都博物馆 content:首都博物馆) (title:首博 content:首博))&start=0&rows=10下面介绍另外一种方法，直接扩展Solr的QParserPlugin。
首先，和前端设计定义统一的接口：
北京OR北平OR首都OR京城OR京都AND首都博物馆OR首博 <=> +((title:北京 content:北京) (title:北平 content:北平) (title:首都 content:首都) (title:京城 content:京城) (title:京都 content:京都)) +((title:首都博物馆 content:首都博物馆) (title:首博 content:首博))我们通过在扩展的QParser中进行解析，代码如下所示：
package org.shirdrn.solr.search;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import org.apache.lucene.index.Term;
import org.apache.lucene.queryParser.ParseException;
import org.apache.lucene.search.BooleanClause;
import org.apache.lucene.search.BooleanQuery;
import org.apache.lucene.search.DisjunctionMaxQuery;
import org.apache.lucene.search.PhraseQuery;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.TermQuery;
import org.apache.solr.common.params.CommonParams;
import org.apache.solr.common.params.DefaultSolrParams;
import org.apache.solr.common.params.DisMaxParams;
import org.apache.solr.common.params.SolrParams;
import org.apache.solr.request.SolrQueryRequest;
import org.apache.solr.search.DisMaxQParser;
import org.apache.solr.util.SolrPluginUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Customized solr QParser of the plugin
*
* @author shirdrn 2011/11/03
*/
public class SimpleQParser extends DisMaxQParser {
private final Logger LOG = LoggerFactory.getLogger(SimpleQParser.class);
// using low level Term query? For internal search usage.
private boolean useLowLevelTermQuery = false;
private float tiebreaker = 0f;
private static Float mainBoost = 1.0f;
private static Float frontBoost = 1.0f;
private static Float rearBoost = 1.0f;
private String userQuery = "";
public SimpleQParser(String qstr, SolrParams localParams,
SolrParams params, SolrQueryRequest req) {
super(qstr, localParams, params, req);
}
@Override
public Query parse() throws ParseException {
SolrParams solrParams = localParams == null ? params : new DefaultSolrParams(localParams, params);
queryFields = SolrPluginUtils.parseFieldBoosts(solrParams.getParams(DisMaxParams.QF));
if (0 == queryFields.size()) {
queryFields.put(req.getSchema().getDefaultSearchFieldName(), 1.0f);
}
/* the main query we will execute. we disable the coord because
* this query is an artificial construct
*/
BooleanQuery query = new BooleanQuery(true);
addMainQuery(query, solrParams);
// rewrite q parameter for highlighting
if(useLowLevelTermQuery) {
query = new BooleanQuery(true);
rewriteAndOrQuery(userQuery, query, solrParams);
}
addBoostQuery(query, solrParams);
addBoostFunctions(query, solrParams);
return query;
}
protected void addMainQuery(BooleanQuery query, SolrParams solrParams)throws ParseException {
tiebreaker = solrParams.getFloat(DisMaxParams.TIE, 0.0f);
// get the comma separated list of fields used for payload
/*
* a parser for dealing with user input, which will convert things to
* DisjunctionMaxQueries
*/
SolrPluginUtils.DisjunctionMaxQueryParser up = getParser(queryFields,DisMaxParams.QS, solrParams, tiebreaker);
/* * * Main User Query * * */
parsedUserQuery = null;
userQuery = getString();
altUserQuery = null;
if (userQuery == null || userQuery.trim().length() < 1) {
// If no query is specified, we may have an alternate
altUserQuery = getAlternateUserQuery(solrParams);
query.add(altUserQuery, BooleanClause.Occur.MUST);
} else {
// There is a valid query string
userQuery = SolrPluginUtils.partialEscape(SolrPluginUtils.stripUnbalancedQuotes(userQuery)).toString();
userQuery = SolrPluginUtils.stripIllegalOperators(userQuery).toString();
// use low level Term for constructing TermQuery or BooleanQuery.
// warning: for internal AND, OR query, in order to integrate with Solr for obtaining highlight
String luceneQueryText = userQuery;
String q = solrParams.get(CommonParams.Q);
if(q!=null && (q.indexOf("AND")!=-1 || q.indexOf("OR")!=-1)) {
addBasicAndOrQuery(luceneQueryText, query, solrParams);
luceneQueryText = query.toString();
useLowLevelTermQuery = true;
}
LOG.debug("userQuery=" + luceneQueryText);
parsedUserQuery = getUserQuery(luceneQueryText, up, solrParams);
BooleanQuery rewritedQuery = rewriteQueries(parsedUserQuery);
query.add(rewritedQuery, BooleanClause.Occur.MUST);
}
}
protected void rewriteAndOrQuery(String userQuery, BooleanQuery query, SolrParams solrParams)throws ParseException {
addBasicAndOrQuery(userQuery, query, solrParams);
}
/**
* Parse mixing MUST and SHOULD query defined by us,
* e.g. 首都OR北京OR北平AND首博OR首都博物馆
* @param userQuery
* @param query
* @param solrParams
* @throws ParseException
*/
protected void addBasicAndOrQuery(String userQuery, BooleanQuery query, SolrParams solrParams)throws ParseException {
userQuery = SolrPluginUtils.partialEscape(SolrPluginUtils.stripUnbalancedQuotes(userQuery)).toString();
userQuery = SolrPluginUtils.stripIllegalOperators(userQuery).toString();
LOG.debug("userQuery=" + userQuery);
BooleanQuery parsedUserQuery = new BooleanQuery(true);
String[] a = userQuery.split("\\s*AND\\s*");
String q = "";
if(a.length==0) {
createTermQuery(parsedUserQuery, userQuery);
} if(a.length>=3) {
if(userQuery.indexOf("OR")==-1) { // e.g. 首都AND北京AND北平
BooleanQuery andBooleanQuery = parseAndQuery(a);
parsedUserQuery.add(andBooleanQuery, BooleanClause.Occur.MUST);
}
} else{
if(a.length>0) {
q = a[0].trim();
if(q.indexOf("OR")!=-1 || q.length()>0) {
parsedUserQuery.add(parseOrQuery(q, frontBoost), BooleanClause.Occur.MUST);
}
}
if(a.length==2) {
q = a[1].trim();
if(q.indexOf("OR")!=-1 || q.length()>0) {
parsedUserQuery.add(parseOrQuery(q, rearBoost), BooleanClause.Occur.MUST);
}
}
}
parsedUserQuery.setBoost(mainBoost);
BooleanQuery rewritedQuery = rewriteQueries(parsedUserQuery);
query.add(rewritedQuery, BooleanClause.Occur.MUST);
}
/**
* Parse SHOULD query, e.g. 北京OR北平OR首都
* @param ors
* @param boost
* @return
*/
private BooleanQuery parseOrQuery(String ors, Float boost) {
BooleanQuery bq = new BooleanQuery(true);
for(String or : ors.split("\\s*OR\\s*")) {
if(!or.isEmpty()) {
createTermQuery(bq, or.trim());
}
}
bq.setBoost(boost);
return bq;
}
/**
* Create TermQuery for some term text, query fields.
* @param bq
* @param qsr
*/
private void createTermQuery(BooleanQuery bq, String qsr) {
for(String field : queryFields.keySet()) {
TermQuery tq = new TermQuery(new Term(field, qsr));
if(queryFields.get(field)!=null) {
tq.setBoost(queryFields.get(field));
}
bq.add(tq, BooleanClause.Occur.SHOULD);
}
}
/**
* Parse MUST query, e.g. 首都AND北京AND北平
* @param ands
* @return
*/
private BooleanQuery parseAndQuery(String[] ands) {
BooleanQuery andBooleanQuery = new BooleanQuery(true);
for(String and : ands) {
if(!and.isEmpty()) {
BooleanQuery bq = new BooleanQuery(true);
createTermQuery(bq, and);
andBooleanQuery.add(bq, BooleanClause.Occur.MUST);
}
}
return andBooleanQuery;
}
/**
* Rewrite a query, especially a {@link BooleanQuery}, whose
* subclauses maybe include {@link BooleanQuery}s, {@link DisjunctionMaxQuery}s,
* {@link TermQuery}s, {@link PhraseQuery}s, {@link PayloadQuery}s, etc.
* @param input
* @return
*/
private BooleanQuery rewriteQueries(Query input) {
BooleanQuery output = new BooleanQuery(true);
if(input instanceof BooleanQuery) {
BooleanQuery bq = (BooleanQuery) input;
for(BooleanClause clause : bq.clauses()) {
if(clause.getQuery() instanceof DisjunctionMaxQuery) {
BooleanClause.Occur occur = clause.getOccur();
output.add(rewriteDisjunctionMaxQueries((DisjunctionMaxQuery) clause.getQuery()), occur); // BooleanClause.Occur.SHOULD
} else {
output.add(clause.getQuery(), clause.getOccur());
}
}
} else if(input instanceof DisjunctionMaxQuery) {
output.add(rewriteDisjunctionMaxQueries((DisjunctionMaxQuery) input), BooleanClause.Occur.SHOULD); // BooleanClause.Occur.SHOULD
}
output.setBoost(input.getBoost()); // boost main clause
return output;
}
/**
* Rewrite the {@link DisjunctionMaxQuery}, because of default parsing
* query string to {@link PhraseQuery}s which are not what we want.
* @param input
* @return
*/
private BooleanQuery rewriteDisjunctionMaxQueries(DisjunctionMaxQuery input) {
// input e.g. (content:"吉林 长白山 内蒙古 九寨沟" | title:"吉林 长白山 内蒙古 九寨沟"^1.5)~1.0
Map<String, BooleanQuery> m = new HashMap<String, BooleanQuery>();
Iterator<Query> iter = input.iterator();
while (iter.hasNext()) {
Query query = iter.next();
if(query instanceof PhraseQuery) {
PhraseQuery pq = (PhraseQuery) query; // e.g. content:"吉林 长白山 内蒙古 九寨沟"
for(Term term : pq.getTerms()) {
BooleanQuery fieldsQuery = m.get(term.text());
if(fieldsQuery==null) {
fieldsQuery = new BooleanQuery(true);
m.put(term.text(), fieldsQuery);
}
fieldsQuery.setBoost(pq.getBoost());
fieldsQuery.add(new TermQuery(term), BooleanClause.Occur.SHOULD);
}
} else if(query instanceof TermQuery) {
TermQuery termQuery = (TermQuery) query;
BooleanQuery fieldsQuery = m.get(termQuery.getTerm().text());
if(fieldsQuery==null) {
fieldsQuery = new BooleanQuery(true);
m.put(termQuery.getTerm().text(), fieldsQuery);
}
fieldsQuery.setBoost(termQuery.getBoost());
fieldsQuery.add(termQuery, BooleanClause.Occur.SHOULD);
}
}
Iterator<Entry<String, BooleanQuery>> it = m.entrySet().iterator();
BooleanQuery mustBooleanQuery = new BooleanQuery(true);
while(it.hasNext()) {
Entry<String, BooleanQuery> entry = it.next();
BooleanQuery shouldBooleanQuery = new BooleanQuery(true);
createTermQuery(shouldBooleanQuery, entry.getKey());
mustBooleanQuery.add(shouldBooleanQuery, BooleanClause.Occur.MUST);
}
return mustBooleanQuery;
}
}接下来，QParser的plugin只需要使用上面实现SimpleQParser，非常容易，如下所示：
package org.shirdrn.solr.search;
import org.apache.solr.common.params.SolrParams;
import org.apache.solr.common.util.NamedList;
import org.apache.solr.request.SolrQueryRequest;
import org.apache.solr.search.QParser;
import org.apache.solr.search.QParserPlugin;
/**
*
* Simple query parser plugin.
* e.g. search "Tokyo AND food"
*
* @author shirdrn
* @date 2011-11-03
*/
public class SimpleQParserPlugin extends QParserPlugin {
@SuppressWarnings("rawtypes")
@Override
public void init(NamedList args) {
}
@Override
public QParser createParser(String qstr, SolrParams localParams,
SolrParams params, SolrQueryRequest req) {
return new SimpleQParser(qstr, localParams,params, req);
}
} <queryParser name="simple" class="org.shirdrn.solr.search.SimpleQParserPlugin" />
<requestHandler name="/simple" class="solr.SearchHandler">
<lst name="defaults">
<str name="defType">simple</str>
<str name="qf">title^1.5 content</str>
<str name="bf">recip(ms(NOW,publishDate),3.16e-13,1,1)^1.68</str>
<str name="mainBoost">1.555</str>
<str name="frontBoost">1.333</str>
<str name="rearBoost">1.222</str>
<str name="fl">*,score</str>
<str name="qt">standard</str>
<str name="wt">standard</str>
<str name="version">2.2</str>
<str name="echoParams">explicit</str>
<bool name="hl">true</bool>
<str name="hl.fl">title content</str>
<int name="hl.snippets">3</int>
<str name="indent">true</str>
<str name="debugQuery">on</str>
<str name="explainOther">on</str>
</lst>
</requestHandler>http://192.168.0.181:8080/solr/core/simple/?q=北京OR北平OR首都OR京城OR京都AND首都博物馆OR首博&start=0&rows=10就能达到我们的目的，搜索结果的xml格式响应，如下所示：
<result name="response" numFound="710" start="0" maxScore="2.5198267">
... ...
<lst name="debug">
<str name="rawquerystring">北京OR北平OR首都OR京城OR京都AND首都博物馆OR首博</str>
<str name="querystring">北京OR北平OR首都OR京城OR京都AND首都博物馆OR首博</str>
<str name="parsedquery">
+((+((content:北京 title:北京^1.5 content:北平 title:北平^1.5 content:首都 title:首都^1.5 content:京城 title:京城^1.5 content:京都 title:京都^1.5)^1.333) +((content:首都博物馆 title:首都博物馆^1.5 content:首博 title:首博^1.5)^1.222))^1.555) FunctionQuery(1.0/(3.16E-13*float(ms(const(1320330543420),date(publishDate)))+1.0))
</str>
<str name="parsedquery_toString">
+((+((content:北京 title:北京^1.5 content:北平 title:北平^1.5 content:首都 title:首都^1.5 content:京城 title:京城^1.5 content:京都 title:京都^1.5)^1.333) +((content:首都博物馆 title:首都博物馆^1.5 content:首博 title:首博^1.5)^1.222))^1.555) 1.0/(3.16E-13*float(ms(const(1320330543420),date(publishDate)))+1.0)
</str>
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