elasticsearch 关联查询对比
两种方式 嵌套和父子关联 Nested Nested docs are stored in the same Lucene block as each other, which helps read/query performance. Reading a nested doc is faster than the equivalent parent/child. Updating a single field in a nested document (parent or nested children) forces ES to reindex the entire nested document. This can be very expensive for large nested docs "Cross referencing" nested documents is impossible Best suited for data that does not change frequently Parent/Child Children are stored separately from the parent, but are routed to the same shard. So parent/children are slightly less performance on read/query than nested Parent/child mappings have a bit extra memory overhead, since ES maintains a "join" list in memory Updating a child doc does not affect the parent or any other children, which can potentially save a lot of indexing on large docs Sorting/scoring can be difficult with Parent/Child since the Has Child/Has Parent operations can be opaque at times 综上所述，两种方式均有利弊，官方建议，自己处理关联关系，减轻ES的压力。 本文转自whk66668888 51CTO博客，原文链接:http://blog.51cto.com/12597095/1904058
