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基于SolrCloud的内容搜索和热点推送

什么是热点

我认为热点有时效性和受众面

用户关注从低到高再到低的内容。有公共热点和分类热点。例如医辽养老全民关注，科技汽车等只有特定的人群关注。

推送的条件

搜索频次达到一定数量

单位时间内搜索频次上升一定倍数。例如1000一周内达到100万，这样就达到推送标准了。

问题背景

自动提示功能是所有搜索应用的标准配置，目的主要有两个

1．提供更好的用户体验，降低输入的复杂度。

2．避免用户输入错误的词，将用户的输入引导向正确的词。弱化同义词处理的重要性

需求分析

海量数据的快速搜索
支持自动提示功能
支持自动纠错
在输入舌尖时，要自动提示舌尖上的中国，舌尖上的小吃等
支持拼音和缩写笔错拼例如shejian sjsdzg shenjianshang shejiashang
查询记录，按照用户的搜索历史优先上排查询频率最高的。
分类热点进行推送

解决方案

索引

Solr的全文件检索有两步

1、创建索引

2、搜索索引

索引是如何创建的又是如何查找的？

Solr采用的一种策略是倒排索引，什么是倒排索引。Solr的倒排索引是如何实现的

大家参考以下三篇文章写的很全。

http://www.cnblogs.com/

forfuture1978/p/3940965.html

http://www.cnblogs.com/

forfuture1978/p/3944583.html

http://www.cnblogs.com/

forfuture1978/p/3945755.html

汉字转拼音

用户输入的关键字可能是汉字、数字，英文，拼音，特殊字符等等，由于需要实现拼音提示，我们需要把汉字转换成拼音，java中考虑使用pinyin4j组件实现转换。

拼音缩写提取

考虑到需要支持拼音缩写，汉字转换拼音的过程中，顺便提取出拼音缩写，如“shejian”,--->"sj”。

自动提示功能

方案一：

在solr中内置了智能提示功能，叫做Suggest模块，该模块可选择基于提示词文本做智能提示，还支持通过针对索引的某个字段建立索引词库做智能提示。使用说明http://wiki.apache.org/solr/Suggester

Suggest存在一些问题，它完全使用freq排序算法，返回的结果完全基于索引中出现的次数，没有兼容搜索的频率，但是我们必须要得到搜索的频率。

我们可以定制SuggestWordScoreComparator重写compare(SuggestWord first, SuggestWord second)方法来实现自己的排序算法。笔者使用了搜索频率和freq权重7:3的方式

方案二：

我们考虑专门为关键字建立一个索引collection，利用solr前缀查询实现。solr中的copyField能很好解决我们同时索引多个字段(汉字、pinyin, abbre)的需求，且field的multiValued属性设置为true时能解决同一个关键字的多音字组合问题。配置如下：

schema.xml:

<field name="keyword" type="string" indexed="true" stored="true" />   <field name="pinyin" type="string" indexed="true" stored="false" multiValued="true"/> <field name="abbre" type="string" indexed="true" stored="false" multiValued="true"/> <field name="kwfreq" type="int" indexed="true" stored="true" /> <field name="_version_" type="long" indexed="true" stored="true"/> <field name="suggest" type="suggest_text" indexed="true" stored="false" multiValued="true" />  <!--multiValued表示字段是多值的-->  <uniqueKey>keyword</uniqueKey> <defaultSearchField>suggest</defaultSearchField>  <copyField source="kw" dest="suggest" /> <copyField source="pinyin" dest="suggest" /> <copyField source="abbre" dest="suggest" />  <!--suggest_text-->  <fieldType name="suggest_text" class="solr.TextField" positionIncrementGap="100" autoGeneratePhraseQueries="true">     <analyzer type="index">             <tokenizer class="solr.KeywordTokenizerFactory" />             <filter class="solr.SynonymFilterFactory"                      synonyms="synonyms.txt"                      ignoreCase="true"                      expand="true" />                      <filter class="solr.StopFilterFactory"                      ignoreCase="true"                      words="stopwords.txt"                      enablePositionIncrements="true" />             <filter class="solr.LowerCaseFilterFactory" />             <filter class="solr.KeywordMarkerFilterFactory" protected="protwords.txt" />     </analyzer>     <analyzer type="query">             <tokenizer class="solr.KeywordTokenizerFactory" />             <filter class="solr.StopFilterFactory"                      ignoreCase="true"                      words="stopwords.txt"                      enablePositionIncrements="true" />             <filter class="solr.LowerCaseFilterFactory" />             <filter class="solr.KeywordMarkerFilterFactory" protected="protwords.txt" />     </analyzer> </fieldType>

SpellCheckComponent拼写纠错

拼写检查的核心是求相似度

两个给定字符串S1和S2的Jaro Distance为：

基于SolrCloud的内容搜索和热点推送

m是匹配的字符数；
t是换位的数目。

两个分别来自S1和S2的字符如果相距不超过基于SolrCloud的内容搜索和热点推送时，我们就认为这两个字符串是匹配的；而这些相互匹配的字符则决定了换位的数目t，简单来说就是不同顺序的匹配字符的数目的一半即为换位的数目t，举例来说，MARTHA与MARHTA的字符都是匹配的，但是这些匹配的字符中，T和H要换位才能把MARTHA变为MARHTA,那么T和H就是不同的顺序的匹配字符，t=2/2=1.

那么这两个字符串的Jaro Distance即为:

基于SolrCloud的内容搜索和热点推送

而Jaro-Winkler则给予了起始部分就相同的字符串更高的分数，他定义了一个前缀p，给予两个字符串，如果前缀部分有长度为的部分相同，则Jaro-Winkler Distance为：

dj是两个字符串的Jaro Distance
是前缀的相同的长度，但是规定最大为4
p则是调整分数的常数，规定不能超过0.25，不然可能出现dw大于1的情况，Winkler将这个常数定义为0.1

这样，上面提及的MARTHA和MARHTA的Jaro-Winkler Distance为：

dw = 0.944 + (3 * 0.1(1 − 0.944)) = 0.961

以上资料来源于维基百科：

http://en.wikipedia.org/wiki/Jaro-Winkler_distance

solr内置了自动纠错的实现spellchecker

我们来分析一下spellchecker的源码

package org.apache.lucene.search.spell;  import java.io.Closeable; import java.io.IOException; import java.util.ArrayList; import java.util.Comparator; import java.util.Iterator; import java.util.List; import org.apache.lucene.document.Document; import org.apache.lucene.document.Field; import org.apache.lucene.document.Field.Store; import org.apache.lucene.document.FieldType; import org.apache.lucene.document.StringField; import org.apache.lucene.index.AtomicReader; import org.apache.lucene.index.AtomicReaderContext; import org.apache.lucene.index.DirectoryReader; import org.apache.lucene.index.FieldInfo.IndexOptions; import org.apache.lucene.index.IndexReader; import org.apache.lucene.index.IndexWriter; import org.apache.lucene.index.IndexWriterConfig; import org.apache.lucene.index.IndexWriterConfig.OpenMode; import org.apache.lucene.index.Term; import org.apache.lucene.index.Terms; import org.apache.lucene.index.TermsEnum; import org.apache.lucene.search.BooleanClause; import org.apache.lucene.search.BooleanClause.Occur; import org.apache.lucene.search.BooleanQuery; import org.apache.lucene.search.IndexSearcher; import org.apache.lucene.search.Query; import org.apache.lucene.search.ScoreDoc; import org.apache.lucene.search.TermQuery; import org.apache.lucene.search.TopDocs; import org.apache.lucene.store.AlreadyClosedException; import org.apache.lucene.store.Directory; import org.apache.lucene.util.BytesRef; import org.apache.lucene.util.BytesRefIterator; import org.apache.lucene.util.Version;  public class SpellChecker implements Closeable {  /*   * DEFAULT_ACCURACY表示默认的最小分数   * SpellCheck会对字典里的每个词与用户输入的搜索关键字进行一个相似度打分   * 默认该值是0.5，相似度分值范围是0到1之间，数字越大表示越相似。   */  public static final float DEFAULT_ACCURACY = 0.5F;  public static final String F_WORD = "word";  //拼写索引目录  Directory spellIndex;    //前缀ngram权重  private float bStart = 2.0F;  //后缀ngram的权重  private float bEnd = 1.0F;  //ngram算法：该算法基于这样一种假设，第n个词的出现只与前面N-1个词相关，而与其它任何词都不相关，整句的概率就是各个词出现概率的乘积。  //简单说ngram就是按定长来分割字符串成多个Term 例如 abcde 3ngram分会得到 abc bcd cde ，4ngram会得到abcd bcde  //索引的查询器对象  private IndexSearcher searcher;  private final Object searcherLock = new Object();  private final Object modifyCurrentIndexLock = new Object();  private volatile boolean closed = false;  private float accuracy = 0.5F;  private StringDistance sd;  private Comparator<SuggestWord> comparator;   public SpellChecker(Directory spellIndex, StringDistance sd) throws IOException {   this(spellIndex, sd, SuggestWordQueue.DEFAULT_COMPARATOR);  }   public SpellChecker(Directory spellIndex) throws IOException {   this(spellIndex, new LevensteinDistance());  }    public SpellChecker(Directory spellIndex, StringDistance sd, Comparator<SuggestWord> comparator)    throws IOException {   setSpellIndex(spellIndex);   setStringDistance(sd);   this.comparator = comparator;  }   public void setSpellIndex(Directory spellIndexDir) throws IOException {   synchronized (this.modifyCurrentIndexLock) {    ensureOpen();    if (!DirectoryReader.indexExists(spellIndexDir)) {     IndexWriter writer = new IndexWriter(spellIndexDir,       new IndexWriterConfig(Version.LUCENE_CURRENT, null));      writer.close();    }    swapSearcher(spellIndexDir);   }  }    public void setComparator(Comparator<SuggestWord> comparator) {   this.comparator = comparator;  }   public Comparator<SuggestWord> getComparator() {   return this.comparator;  }   public void setStringDistance(StringDistance sd) {   this.sd = sd;  }   public StringDistance getStringDistance() {   return this.sd;  }   public void setAccuracy(float acc) {   this.accuracy = acc;  }    public float getAccuracy() {   return this.accuracy;  }   public String[] suggestSimilar(String word, int numSug) throws IOException {   return suggestSimilar(word, numSug, null, null, SuggestMode.SUGGEST_WHEN_NOT_IN_INDEX);  }   public String[] suggestSimilar(String word, int numSug, float accuracy) throws IOException {   return suggestSimilar(word, numSug, null, null, SuggestMode.SUGGEST_WHEN_NOT_IN_INDEX, accuracy);  }   public String[] suggestSimilar(String word, int numSug, IndexReader ir, String field, SuggestMode suggestMode)    throws IOException {   return suggestSimilar(word, numSug, ir, field, suggestMode, this.accuracy);  }    /*   * 核心重点   */  public String[] suggestSimilar(String word, int numSug, IndexReader ir, String field, SuggestMode suggestMode,    float accuracy) throws IOException {   IndexSearcher indexSearcher = obtainSearcher();   try {    if ((ir == null) || (field == null)) {     //SuggestMode.SUGGEST_ALWAYS永远建议     suggestMode = SuggestMode.SUGGEST_ALWAYS;    }    if (suggestMode == SuggestMode.SUGGEST_ALWAYS) {     ir = null;     field = null;    }    int lengthWord = word.length();     int freq = (ir != null) && (field != null) ? ir.docFreq(new Term(field, word)) : 0;    int goalFreq = suggestMode == SuggestMode.SUGGEST_MORE_POPULAR ? freq : 0;    // freq > 0表示用记搜索的关键词在SuggestMode.SUGGEST_WHEN_NOT_IN_INDEX为空，才提供建议       if ((suggestMode == SuggestMode.SUGGEST_WHEN_NOT_IN_INDEX) && (freq > 0)) {     return new String[] { word };    }    BooleanQuery query = new BooleanQuery();    for (int ng = getMin(lengthWord); ng <= getMax(lengthWord); ng++) {     String key = "gram" + ng;      String[] grams = formGrams(word, ng);     if (grams.length != 0) {      if (this.bStart > 0.0F) {       add(query, "start" + ng, grams[0], this.bStart);      }      if (this.bEnd > 0.0F) {       add(query, "end" + ng, grams[(grams.length - 1)], this.bEnd);      }      for (int i = 0; i < grams.length; i++) {       add(query, key, grams[i]);       }     }    }    int maxHits = 10 * numSug;     ScoreDoc[] hits = indexSearcher.search(query, null, maxHits).scoreDocs;     SuggestWordQueue sugQueue = new SuggestWordQueue(numSug, this.comparator);     int stop = Math.min(hits.length, maxHits);    SuggestWord sugWord = new SuggestWord();    for (int i = 0; i < stop; i++) {     sugWord.string = indexSearcher.doc(hits[i].doc).get("word");     if (!sugWord.string.equals(word)) {      sugWord.score = this.sd.getDistance(word, sugWord.string);      //求关键字和索引中的Term的相似度      if (sugWord.score >= accuracy) {       if ((ir != null) && (field != null)) {        sugWord.freq = ir.docFreq(new Term(field, sugWord.string));        //如果相似度小于设置的默认值则也不返回        if (((suggestMode == SuggestMode.SUGGEST_MORE_POPULAR) && (goalFreq > sugWord.freq))        || (sugWord.freq < 1)) {        }       } else {        //条件符合那就把当前索引中的Term存入拼写建议队列中        //如果队列满了则把队列顶部的score(即相似度)缓存到accuracy即该值就表示了当前最小的相似度值，        //当队列满了，把相似度最小的移除        sugQueue.insertWithOverflow(sugWord);        if (sugQueue.size() == numSug) {         accuracy = ((SuggestWord) sugQueue.top()).score;        }        sugWord = new SuggestWord();       }      }     }    }    String[] list = new String[sugQueue.size()];    for (int i = sugQueue.size() - 1; i >= 0; i--) {     list[i] = ((SuggestWord) sugQueue.pop()).string;    }    return list;   } finally {   releaseSearcher(indexSearcher);   }  }   private static void add(BooleanQuery q, String name, String value, float boost) {   Query tq = new TermQuery(new Term(name, value));   tq.setBoost(boost);   q.add(new BooleanClause(tq, BooleanClause.Occur.SHOULD));  }   private static void add(BooleanQuery q, String name, String value) {   q.add(new BooleanClause(new TermQuery(new Term(name, value)), BooleanClause.Occur.SHOULD));  }   /*   * 根据ng的长度对text字符串进行 ngram分词   */       private static String[] formGrams(String text, int ng) {   int len = text.length();   String[] res = new String[len - ng + 1];   for (int i = 0; i < len - ng + 1; i++) {    res[i] = text.substring(i, i + ng);   }   return res;  }   public void clearIndex() throws IOException {   synchronized (this.modifyCurrentIndexLock) {    ensureOpen();    Directory dir = this.spellIndex;    IndexWriter writer = new IndexWriter(dir,      new IndexWriterConfig(Version.LUCENE_CURRENT, null).setOpenMode(IndexWriterConfig.OpenMode.CREATE));           writer.close();    swapSearcher(dir);   }  }   public boolean exist(String word) throws IOException {   IndexSearcher indexSearcher = obtainSearcher();   try {    return indexSearcher.getIndexReader().docFreq(new Term("word", word)) > 0;   } finally {    releaseSearcher(indexSearcher);   }  }   /*   * 这个比较难理解   */    public final void indexDictionary(Dictionary dict, IndexWriterConfig config, boolean fullMerge)     throws IOException   {     synchronized (this.modifyCurrentIndexLock)     {       ensureOpen();       Directory dir = this.spellIndex;       IndexWriter writer = new IndexWriter(dir, config);       IndexSearcher indexSearcher = obtainSearcher();       List<TermsEnum> termsEnums = new ArrayList();       //读取索引目录       IndexReader reader = this.searcher.getIndexReader();       if (reader.maxDoc() > 0) {       //加载word域上的所有Term存入TermEnum集合         for (AtomicReaderContext ctx : reader.leaves())         {         Terms terms = ctx.reader().terms("word");                      if (terms != null) {             termsEnums.add(terms.iterator(null));           }         }       }       boolean isEmpty = termsEnums.isEmpty();       try       {      //加载字典文件         BytesRefIterator iter = dict.getEntryIterator();         BytesRef currentTerm;         //遍历字典文件里的每个词         while ((currentTerm = iter.next()) != null)         {           String word = currentTerm.utf8ToString();           int len = word.length();           if (len >= 3)           {            if (!isEmpty)             {               Iterator i$ = termsEnums.iterator();               for (;;)               {                                if (!i$.hasNext()) {                   break label235;                 }                 //遍历索引目录里word域上的每个Term                 TermsEnum te = (TermsEnum)i$.next();                                  if (te.seekExact(currentTerm)) {                   break;                 }               }             }             label235:             //通过ngram分成多个Term             Document doc = createDocument(word, getMin(len), getMax(len));             //将字典文件里当前词写入索引              writer.addDocument(doc);           }         }       }       finally       {         releaseSearcher(indexSearcher);       }       if (fullMerge) {         writer.forceMerge(1);       }       writer.close();              swapSearcher(dir);     }   }   private static int getMin(int l) {   if (l > 5) {    return 3;   }     if (l == 5) {    return 2;   }   return 1;  }   private static int getMax(int l) {   if (l > 5) {    return 4;   }   if (l == 5) {    return 3;   }   return 2;  }   private static Document createDocument(String text, int ng1, int ng2) {   Document doc = new Document();      Field f = new StringField("word", text, Field.Store.YES);   doc.add(f);   addGram(text, doc, ng1, ng2);   return doc;  }   private static void addGram(String text, Document doc, int ng1, int ng2) {   int len = text.length();   for (int ng = ng1; ng <= ng2; ng++) {    String key = "gram" + ng;    String end = null;    for (int i = 0; i < len - ng + 1; i++) {     String gram = text.substring(i, i + ng);     FieldType ft = new FieldType(StringField.TYPE_NOT_STORED);     ft.setIndexOptions(FieldInfo.IndexOptions.DOCS_AND_FREQS);     Field ngramField = new Field(key, gram, ft);          doc.add(ngramField);     if (i == 0) {      Field startField = new StringField("start" + ng, gram, Field.Store.NO);      doc.add(startField);     }     end = gram;    }    if (end != null) {     Field endField = new StringField("end" + ng, end, Field.Store.NO);     doc.add(endField);    }   }  }   private IndexSearcher obtainSearcher() {   synchronized (this.searcherLock) {    ensureOpen();    this.searcher.getIndexReader().incRef();    return this.searcher;   }  }   private void releaseSearcher(IndexSearcher aSearcher) throws IOException {   aSearcher.getIndexReader().decRef();  }   private void ensureOpen() {   if (this.closed) {    throw new AlreadyClosedException("Spellchecker has been closed");   }  }   public void close() throws IOException {   synchronized (this.searcherLock) {    ensureOpen();    this.closed = true;    if (this.searcher != null) {     this.searcher.getIndexReader().close();     }    this.searcher = null;   }  }   private void swapSearcher(Directory dir) throws IOException {   IndexSearcher indexSearcher = createSearcher(dir);   synchronized (this.searcherLock) {    if (this.closed) {     indexSearcher.getIndexReader().close();     throw new AlreadyClosedException("Spellchecker has been closed");    }    if (this.searcher != null) {     this.searcher.getIndexReader().close();    }    this.searcher = indexSearcher;    this.spellIndex = dir;   }  }  IndexSearcher createSearcher(Directory dir) throws IOException {   return new IndexSearcher(DirectoryReader.open(dir));  }   boolean isClosed() {   return this.closed;  } }

以上我们就建立的一个符合要求的检索功能，然后再从中筛选热点，根据用户画像分类推送就可以了。