# Hard to understand Elasticsearch optimization article
**URL:** https://discuss.elastic.co/t/hard-to-understand-elasticsearch-optimization-article/121153
**Category:** Elasticsearch
**Created:** [February 23, 2018, 3:04am UTC](https://discuss.elastic.co/t/hard-to-understand-elasticsearch-optimization-article/121153 "2018-02-23T03:04:32Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@elasticdude](https://discuss.elastic.co/u/elasticdude)
#### Post date: [February 23, 2018, 3:04am UTC](https://discuss.elastic.co/t/hard-to-understand-elasticsearch-optimization-article/121153/1 "2018-02-23T03:04:32Z")
I read the [article](https://blog.discordapp.com/how-discord-indexes-billions-of-messages-e3d5e9be866f) about optimizing Elasticsearch table but I'm not able to understand what does author mean by following line.
> These fields however aren’t actually “stored” in Elasticsearch, rather, they are only stored in the inverted index.
Can anyone please explain? It would be great if you can also explain about \_source field.
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### Author:  [@warkolm](https://discuss.elastic.co/u/warkolm)
#### Post date: [March 8, 2018, 11:28pm UTC](https://discuss.elastic.co/t/hard-to-understand-elasticsearch-optimization-article/121153/2 "2018-03-08T23:28:02Z")
When a field is stored, it means you can have the value of the field returned in a search result. If you don't store it then you will know that it exists in a search result, but you won't know what the result actually is.
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [April 5, 2018, 11:28pm UTC](https://discuss.elastic.co/t/hard-to-understand-elasticsearch-optimization-article/121153/3 "2018-04-05T23:28:09Z")
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