# Nested objects indexing and efficiency

**URL:** <https://discuss.elastic.co/t/nested-objects-indexing-and-efficiency/78464>\
**Category:** Elasticsearch\
**Created:** [March 14, 2017, 8:07am UTC](https://discuss.elastic.co/t/nested-objects-indexing-and-efficiency/78464 "2017-03-14T08:07:19Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Eyal\_Israeli](https://avatars.discourse-cdn.com/v4/letter/e/e274bd/32.png) [@Eyal\_Israeli](https://discuss.elastic.co/u/Eyal_Israeli)\
**Post date:** [March 14, 2017, 8:07am UTC](https://discuss.elastic.co/t/nested-objects-indexing-and-efficiency/78464/1 "2017-03-14T08:07:19Z")

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I'm trying to figure out the modeling and mapping which will be best suited for me, and have some questions regarding the Nested object concept, specifically the hidden document concept:

1. How a mapping for a nested object will look like? It cannot be flatten like an object-type field, so what's this "magic" that make this joinable fastly ([https://www.elastic.co/guide/en/elasticsearch/guide/master/nested-objects.html#nested-objects](https://www.elastic.co/guide/en/elasticsearch/guide/master/nested-objects.html#nested-objects)) ?
2. Can someone elaborate about the disk space efficiency when using a nested object?

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**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [April 11, 2017, 8:07am UTC](https://discuss.elastic.co/t/nested-objects-indexing-and-efficiency/78464/2 "2017-04-11T08:07:29Z")

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Closed on April 11, 2017, 8:07am UTC

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