[[breaking_50_aggregations_changes]]
=== Aggregation changes

==== Significant terms on numeric fields

Numeric fields have been refactored to use a different data structure that
performs better for range queries. However, since this data structure does
not record document frequencies, numeric fields need to fall back to running
queries in order to estimate the number of matching documents in the
background set, which may incur a performance degradation.

It is recommended to use <<keyword,`keyword`>> fields instead, either directly
or through a <<multi-fields,multi-field>> if the numeric representation is
still needed for sorting, range queries or numeric aggregations like
<<search-aggregations-metrics-stats-aggregation,`stats` aggregations>>.