OpenSearch/docs/reference/migration/migrate_5_0/mapping.asciidoc

[[breaking_50_mapping_changes]]
=== Mapping changes

==== `string` fields replaced by `text`/`keyword` fields

The `string` field datatype has been replaced by the `text` field for full
text analyzed content, and the `keyword` field for not-analyzed exact string
values.  For backwards compatibility purposes, during the 5.x series:

* `string` fields on pre-5.0 indices will function as before.
* New `string` fields can be added to pre-5.0 indices as before.
* `text` and `keyword` fields can also be added to pre-5.0 indices.
* When adding a `string` field to a new index, the field mapping will be
  rewritten as a `text` or `keyword` field if possible, otherwise
  an exception will be thrown.  Certain configurations that were possible
  with `string` fields are no longer possible with `text`/`keyword` fields
  such as enabling `term_vectors` on a not-analyzed `keyword` field.

==== Default string mappings

String mappings now have the following default mappings:

[source,js]
---------------
{
  "type": "text",
  "fields": {
    "keyword": {
      "type": "keyword",
      "ignore_above": 256
    }
  }
}
---------------

This allows to perform full-text search on the original field name and to sort
and run aggregations on the sub keyword field.

==== Numeric fields

Numeric fields are now indexed with a completely different data-structure, called
BKD tree, that is expected to require less disk space and be faster for range
queries than the previous way that numerics were indexed.

Term queries will return constant scores now, while they used to return higher
scores for rare terms due to the contribution of the document frequency, which
this new BKD structure does not record. If scoring is needed, then it is advised
to map the numeric fields as <<keyword,`keyword`s>> too.

Note that this <<keyword,`keyword`>> mapping do not need to replace the numeric
mapping. For instance if you need both sorting and scoring on your numeric field,
you could map it both as a number and a `keyword` using <<multi-fields>>:

[source,js]
--------------------------------------------------
PUT my_index
{
  "mappings": {
    "my_type": {
      "properties": {
        "my_number": {
          "type": "long",
          "fields": {
            "keyword": {
              "type":  "keyword"
            }
          }
        }
      }
    }
  }
}
--------------------------------------------------
// CONSOLE

Also the `precision_step` parameter is now irrelevant and will be rejected on
indices that are created on or after 5.0.

==== `index` property

On all field datatypes (except for the deprecated `string` field), the `index`
property now only accepts `true`/`false` instead of `not_analyzed`/`no`. The
`string` field still accepts `analyzed`/`not_analyzed`/`no`.

==== Doc values on unindexed fields

Previously, setting a field to `index:no` would also disable doc-values.  Now,
doc-values are always enabled on numeric and boolean fields unless
`doc_values` is set to `false`.

==== Floating points use `float` instead of `double`

When dynamically mapping a field containing a floating point number, the field
now defaults to using `float` instead of `double`. The reasoning is that
floats should be more than enough for most cases but would decrease storage
requirements significantly.

==== `norms`

`norms` now take a boolean instead of an object. This boolean is the replacement
for `norms.enabled`. There is no replacement for `norms.loading` since eager
loading of norms is not useful anymore now that norms are disk-based.

==== `fielddata.format`

Setting `fielddata.format: doc_values` in the mappings used to implicitly
enable doc-values on a field. This no longer works: the only way to enable or
disable doc-values is by using the `doc_values` property of mappings.

==== `fielddata.filter.regex`

Regex filters are not supported anymore and will be dropped on upgrade.

==== Source-transform removed

The source `transform` feature has been removed. Instead, use an ingest pipeline

==== `_parent` field no longer indexed

The join between parent and child documents no longer relies on indexed fields
and therefore from 5.0.0 onwards the `_parent` field is no longer indexed. In
order to find documents that refer to a specific parent id, the new
`parent_id` query can be used. The GET response and hits inside the search
response still include the parent id under the `_parent` key.

==== Source `format` option

The `_source` mapping no longer supports the `format` option. It will still be
accepted for indices created before the upgrade to 5.0 for backwards
compatibility, but it will have no effect. Indices created on or after 5.0
will reject this option.

==== Object notation

Core types no longer support the object notation, which was used to provide
per document boosts as follows:

[source,js]
---------------
{
  "value": "field_value",
  "boost": 42
}
---------------

==== Boost accuracy for queries on `_all`

Per-field boosts on the `_all` are now compressed into a single byte instead
of the 4 bytes used previously. While this will make the index much more
space-efficient, it also means that index time boosts will be less accurately
encoded.