# Questions about field data configuration

**URL:** <https://discuss.elastic.co/t/questions-about-field-data-configuration/16661>\
**Category:** Elasticsearch\
**Created:** [March 27, 2014, 10:46pm UTC](https://discuss.elastic.co/t/questions-about-field-data-configuration/16661 "2014-03-27T22:46:39Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![schmichael](https://avatars.discourse-cdn.com/v4/letter/s/ea5d25/32.png) [@schmichael](https://discuss.elastic.co/u/schmichael)\
**Post date:** [March 27, 2014, 10:46pm UTC](https://discuss.elastic.co/t/questions-about-field-data-configuration/16661/1 "2014-03-27T22:46:39Z")

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I was surprised to find recently that while indices.fielddata.breaker.limit  
defaults to 80% of the heap, indices.fielddata.cache.size is unbounded.

Is there ever a case where you would want breaker.limit \< cache.size?

Is there any reason to cache.expire?

Under what circumstances would you adjust the breaker.overhead?

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**Author:** ![schmichael](https://avatars.discourse-cdn.com/v4/letter/s/ea5d25/32.png) [@schmichael](https://discuss.elastic.co/u/schmichael)\
**Post date:** [April 8, 2014, 6:09pm UTC](https://discuss.elastic.co/t/questions-about-field-data-configuration/16661/2 "2014-04-08T18:09:47Z")

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Chatted with dakrone in IRC and wanted to copy the notes here.

On Thursday, March 27, 2014 3:46:39 PM UTC-7, schmichael wrote:

> I was surprised to find recently that  
> while indices.fielddata.breaker.limit defaults to 80% of the  
> heap, indices.fielddata.cache.size is unbounded.
> 
> Is there ever a case where you would want breaker.limit \< cache.size?

Two cases:  
If the breaker isn't properly estimating cache usage. Since the breaker  
does an initial usage estimate, the actual amount of cache the resultset  
takes may vary from the estimation.

The other case depends on how you want ES to behave. If you prefer  
slow-but-finishes over fast-but-can-fail, then always set the cache size  
lower than the breaker. If you'd rather have pathological queries trip the  
breaker and keep things fast, then don't worry about setting the cache size  
and instead just set the breaker.

> Is there any reason to cache.expire?

Didn't really get a compelling reason for this. Seems minor if it matters  
at all.

> Under what circumstances would you adjust the breaker.overhead?

If you find that the actual fielddata cache usage exceeds your breaker  
limit without actually tripping the breaker, that means the breaker isn't  
estimating cache usage properly. You can adjust the overhead to try to make  
it more accurate.

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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:** [July 6, 2017, 1:37am UTC](https://discuss.elastic.co/t/questions-about-field-data-configuration/16661/3 "2017-07-06T01:37:30Z")

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