Understanding the explain information

Compared to databases, using systems capable of performing full-text search can often be anything other than obvious. We can search in many fields simultaneously and the data in the index can vary from the ones provided as the values of the document fields (because of the analysis process, synonyms, abbreviations, and others). It's even worse! By default, search engines sort data by relevance, which means that each document is given a number indicating how similar the document is to the query. The key point here is understanding the how similar phrase. As we discussed in the beginning of the chapter, scoring takes many factors into account – how many searched words were found in the document, how frequent the word is, how many terms are in the field, and so on. This seems complicated and finding out why a document was found and why another document is better is not easy. Fortunately, Elasticsearch provides us with tools that can answer these questions...