OpenSearch/docs/reference/modules/indices/fielddata.asciidoc

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[[modules-fielddata]]
=== Fielddata
The field data cache is used mainly when sorting on or computing aggregations
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.
`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. Also see
<<fielddata-circuit-breaker>>.
NOTE: These are static settings which must be configured on every data node in
the cluster.
[float]
[[fielddata-monitoring]]
==== Monitoring field data
You can monitor memory usage for field data as well as the field data circuit
breaker using
<<cluster-nodes-stats,Nodes Stats API>>