elasticsearch - Elasticsearch 中doc_values:true的用途是什么？

Question

在Elastic search中，为了映射它们正在使用

doc_values:true，这有什么用？

如果已经问过，请不要忽略。我需要答案。

提前致谢。

Answer 1

从the documentation:

Doc values are now only about 10–25% slower than in-memory fielddata, and come with two major advantages:

• They live on disk instead of in heap memory. This allows you to work with quantities of fielddata that would normally be too large to fit into memory. In fact, your heap space ($ES_HEAP_SIZE) can now be set to a smaller size, which improves the speed of garbage collection and, consequently, node stability.
• Doc values are built at index time, not at search time. While in-memory fielddata has to be built on the fly at search time by uninverting the inverted index, doc values are prebuilt and much faster to initialize.