elasticsearch parent/children aggregation performance

Question

I am just an elasticsearch newbie. According to the following elasticsearch document,

• join datatype

  The join field shouldn’t be used like joins in a relation database. In Elasticsearch the key to good performance is to de-normalize your data into documents. Each join field, has_child or has_parent query adds a significant tax to your query performance.

• has_child query

  Note that the has_child is a slow query compared to other queries in the query dsl due to the fact that it performs a join.

• has_parent query

  Note that the has_parent is a slow query compared to other queries in the query dsl due to the fact that it performs a join.

I can understand these query types are slow and should be avoided. But what about parent and children aggregations ? I can not find any document or performance test result which says these aggregations are slow or not so bad.

I have to test it though, can someone give me some advice ?

Answer 1

Parent and Child Aggregations are definitely slower compared to other Aggregations. I have tested it in my applications and found it much slower than normal ones.