ElasticSearch Cookbook

ElasticSearch — крупнейшая система операционной аналитики с открытым кодом. Позволяет решать задачи в различных сферах, таких как digital intelligence, безопасность, мониторинг ИТ-инфраструктуры и бизнес-аналитика. Как правило, для построения полноценного бизнес-решения используется вместе с другими продуктами, такими как logstash (для сбора данных) и kibana (визуализация данных).

Цитируем:

«The facets are always executed on search hits; they are usually computed in a map/reduce way. The map step is distributed in shards, meanwhile the reduce step is done in the called search server. Because, for facet computation, a lot of data should be kept in memory, they usually require a lot of memory to be executed. For example, executing a term facet requires that all unique terms in the field, which is used for faceting, are kept in memory. Executing this operation on million of documents requires perhaps storing a large number of values in memory. The main usage of facets is to provide additional data to the search results to improve their quality or to extend them with additional information. For example, in searching for news articles, some facets that can be interesting to be calculated could be the authors who wrote the articles and the date histogram of the publishing date».