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概要结构如下图。 图中显示：Search Index和Read Replicas等系统是Databus的消费者。当主OLTP数据库发生写操作时，连接其上的中继系统会将数据拉到中继中。签入在Search Index或是缓存中的Databus消费者客户端，就会从中继中拉出数据，并更新索引或缓存。 Dat 阅读全文
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Ignoring TF/IDF Ignoring TF/IDF Ignoring TF/IDF Ignoring TF/IDF Sometimes we just don’t care about TF/IDF. All we want to know is that a certain word 阅读全文
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Query-Time Boosting Query-Time Boosting Query-Time Boosting Query-Time Boosting In Prioritizing Clauses, we explained how you could use the boost para 阅读全文
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For multiterm queries, Lucene takes the Boolean model, TF/IDF, and the vector space model and combines them in a single efficient package that collect 阅读全文
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Vector Space Model Vector Space Model The vector space model provides a way of comparing a multiterm query against a document. The output is a single 阅读全文
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Theory Behind Relevance Scoring Theory Behind Relevance Scoring Theory Behind Relevance Scoring Theory Behind Relevance Scoring Lucene (and thus Elast 阅读全文
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Field-length norm How long is the field? The shorter the field, the higher the weight. If a term appears in a short field, such as a title field, it i 阅读全文
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When we run a simple term query with explain set to true (see Understanding the Score), you will see that the only factors involved in calculating the 阅读全文
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改变Lucene的打分模型 随着Apache Lucene 4.0版本在2012年的发布，这款伟大的全文检索工具包终于允许用户修改默认的基于TF/IDF原理的打分算法。Lucene API变得更加容易修改和扩展打分公式。但是，对于文档的打分计算，Lucene并只是允许用户在打分公式上修修补补，Luc 阅读全文
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Tuning BM25 Tuning BM25 One of the nice features of BM25 is that, unlike TF/IDF, it has two parameters that allow it to be tuned: k1This parameter con 阅读全文
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Pluggable Similarity Algorithms Before we move on from relevance and scoring, we will finish this chapter with a more advanced subject: pluggable simi 阅读全文
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Elasticsearch allows you to configure a scoring algorithm or similarity per field. The similaritysetting provides a simple way of choosing a similarit 阅读全文