elasticsearch/docs/reference/migration/migrate_8_0/mappings.asciidoc

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[[breaking_80_mappings_changes]]
=== Mapping changes

//NOTE: The notable-breaking-changes tagged regions are re-used in the
//Installation and Upgrade Guide

//tag::notable-breaking-changes[]

// end::notable-breaking-changes[]

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==== Limiting the number of completion contexts

The number of completion contexts within a single completion field
has been limited to 10.

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==== Defining multi-fields within multi-fields

Previously, it was possible to define a multi-field within a multi-field.
Defining chained multi-fields was deprecated in 7.3 and is now no longer
supported. To migrate the mappings, all instances of `fields` that occur within
a `fields` block should be removed, either by flattening the chained `fields`
blocks into a single level, or by switching to `copy_to` if appropriate.

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[[fieldnames-enabling]]
==== Disallow use of the `enabled` setting on the  `_field_names` field

The setting has been deprecated with 7.5 and is no longer supported on new indices.
Mappings for older indices will continue to work but emit a deprecation warning.
The `enabled` setting for `_field_names` should be removed from templates and mappings. 
Disabling _field_names is not necessary because it no longer carries a large index overhead.