Field data

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The field data cache is used mainly when sorting on or faceting on a field. It loads all the field values to memory in order to provide fast document based access to those values. The field data cache can be expensive to build for a field, so its recommended to have enough memory to allocate it, and to keep it loaded.

The amount of memory used for the field data cache can be controlled using indices.fielddata.cache.size. Note: reloading the field data which does not fit into your cache will be expensive and perform poorly.

Setting Description

indices.fielddata.cache.size

The max size of the field data cache, eg 30% of node heap space, or an absolute value, eg 12GB. Defaults to unbounded.

indices.fielddata.cache.expire

A time based setting that expires field data after a certain time of inactivity. Defaults to -1. For example, can be set to 5m for a 5 minute expiry.

Field data circuit breaker

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The field data circuit breaker allows Elasticsearch to estimate the amount of memory a field will require to be loaded into memory. It can then prevent the field data loading by raising an exception. By default the limit is configured to 60% of the maximum JVM heap. It can be configured with the following parameters:

Setting Description

indices.fielddata.breaker.limit

Maximum size of estimated field data to allow loading. Defaults to 60% of the maximum JVM heap.

indices.fielddata.breaker.overhead

A constant that all field data estimations are multiplied with to determine a final estimation. Defaults to 1.03

Both the indices.fielddata.breaker.limit and indices.fielddata.breaker.overhead can be changed dynamically using the cluster update settings API.

Monitoring field data

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You can monitor memory usage for field data as well as the field data circuit breaker using Nodes Stats API