# Choosing Parent/Child vs Nested Document **URL:** \ **Category:** Elasticsearch\ **Created:** [February 18, 2012, 8:31am UTC](https://discuss.elastic.co/t/choosing-parent-child-vs-nested-document/6742 "2012-02-18T08:31:43Z")\ **Posts on this page:** 1\ **Showing post:** 6
**Author:** ![kimchy](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/kimchy/32/44952_2.png) [@kimchy](https://discuss.elastic.co/u/kimchy)\ **Post date:** [February 29, 2012, 1:55pm UTC](https://discuss.elastic.co/t/choosing-parent-child-vs-nested-document/6742/6 "2012-02-29T13:55:38Z")
++Harm On Tuesday, February 28, 2012 at 1:18 PM, haarts wrote: > I'm not Shay (not by a long shot) but I do know the answer to that one! > Your assumption is correct. An update allows you to append stuff to the document without sending it over the wire entirely. It also handles conflicts (see retry\_on\_conflict argument). But the entire document _is_ reindexed which can be rather expensive. Adding tags probably wouldn't be a problem. Added (hundreds of) comments to a blog post is a problem. > > Harm > > On Tuesday, 28 February 2012 11:37:19 UTC+1, Karel Minařík wrote: > > > Shay, do I understand correctly, that the update API [http:// > > [Elasticsearch Platform — Find real-time answers at scale | Elastic](http://www.elasticsearch.org/guide/reference/api/update.html) ([Elasticsearch Platform — Find real-time answers at scale | Elastic](http://www.elasticsearch.org/guide/reference/api/update.html))] enables to > > append "nested" documents to the "main" document, such as adding a tag > > or comment to an article, without requiring to send the full document > > over the wire? (And also without potential conflicts with concurrent > > updates?) > > > > Karel > > > > On Feb 20, 1:58 pm, Shay Banon [kim...@gmail.com](mailto:kim...@gmail.com) wrote: > > > > > Both parent/child or nested documents will have the relevant data reside in the same shard. The main difference is that nested are faster compared to parent/child, but, nested docs require reindexing the parent with all its children, while parent child allows to reindex / add / delete specific children. > > On Tuesday, 28 February 2012 11:37:19 UTC+1, Karel Minařík wrote: > > > Shay, do I understand correctly, that the update API [http:// > > [Elasticsearch Platform — Find real-time answers at scale | Elastic](http://www.elasticsearch.org/guide/reference/api/update.html) ([Elasticsearch Platform — Find real-time answers at scale | Elastic](http://www.elasticsearch.org/guide/reference/api/update.html))] enables to > > append "nested" documents to the "main" document, such as adding a tag > > or comment to an article, without requiring to send the full document > > over the wire? (And also without potential conflicts with concurrent > > updates?) > > > > Karel > > > > On Feb 20, 1:58 pm, Shay Banon [kim...@gmail.com](mailto:kim...@gmail.com) wrote: > > > > > Both parent/child or nested documents will have the relevant data reside in the same shard. The main difference is that nested are faster compared to parent/child, but, nested docs require reindexing the parent with all its children, while parent child allows to reindex / add / delete specific children. > > On Tuesday, 28 February 2012 11:37:19 UTC+1, Karel Minařík wrote: > > > Shay, do I understand correctly, that the update API [http:// > > [Elasticsearch Platform — Find real-time answers at scale | Elastic](http://www.elasticsearch.org/guide/reference/api/update.html) ([Elasticsearch Platform — Find real-time answers at scale | Elastic](http://www.elasticsearch.org/guide/reference/api/update.html))] enables to > > append "nested" documents to the "main" document, such as adding a tag > > or comment to an article, without requiring to send the full document > > over the wire? (And also without potential conflicts with concurrent > > updates?) > > > > Karel > > > > On Feb 20, 1:58 pm, Shay Banon [kim...@gmail.com](mailto:kim...@gmail.com) wrote: > > > > > Both parent/child or nested documents will have the relevant data reside in the same shard. The main difference is that nested are faster compared to parent/child, but, nested docs require reindexing the parent with all its children, while parent child allows to reindex / add / delete specific children. > > On Tuesday, 28 February 2012 11:37:19 UTC+1, Karel Minařík wrote: > > > Shay, do I understand correctly, that the update API [http:// > > [Elasticsearch Platform — Find real-time answers at scale | Elastic](http://www.elasticsearch.org/guide/reference/api/update.html) ([Elasticsearch Platform — Find real-time answers at scale | Elastic](http://www.elasticsearch.org/guide/reference/api/update.html))] enables to > > append "nested" documents to the "main" document, such as adding a tag > > or comment to an article, without requiring to send the full document > > over the wire? (And also without potential conflicts with concurrent > > updates?) > > > > Karel > > > > On Feb 20, 1:58 pm, Shay Banon [kim...@gmail.com](mailto:kim...@gmail.com) wrote: > > > > > Both parent/child or nested documents will have the relevant data reside in the same shard. The main difference is that nested are faster compared to parent/child, but, nested docs require reindexing the parent with all its children, while parent child allows to reindex / add / delete specific children. --- _[View the full topic](https://discuss.elastic.co/t/choosing-parent-child-vs-nested-document/6742)._