[[breaking_20_mapping_changes]]
=== Mapping changes

A number of changes have been made to mappings to remove ambiguity and to
ensure that conflicting mappings cannot be created.

One major change is that dynamically added fields must have their mapping
confirmed by the master node before indexing continues.  This is to avoid a
problem where different shards in the same index dynamically add different
mappings for the same field.  These conflicting mappings can silently return
incorrect results and can lead to index corruption.

This change can make indexing slower when frequently adding many new fields.
We are looking at ways of optimising this process but we chose safety over
performance for this extreme use case.

==== Conflicting field mappings

Fields with the same name, in the same index, in different types, must have
the same mapping, with the exception of the <<copy-to>>, <<dynamic>>,
<<enabled>>, <<ignore-above>>, <<include-in-all>>, and <<properties>>
parameters, which may have different settings per field.

[source,js]
---------------
PUT my_index
{
  "mappings": {
    "type_one": {
      "properties": {
        "name": { <1>
          "type": "string"
        }
      }
    },
    "type_two": {
      "properties": {
        "name": { <1>
          "type":     "string",
          "analyzer": "english"
        }
      }
    }
  }
}
---------------
<1> The two `name` fields have conflicting mappings and will prevent Elasticsearch
    from starting.

Elasticsearch will not start in the presence of conflicting field mappings.
These indices must be deleted or reindexed using a new mapping.

The `ignore_conflicts` option of the put mappings API has been removed.
Conflicts can't be ignored anymore.

==== Fields cannot be referenced by short name

A field can no longer be referenced using its short name.  Instead, the full
path to the field is required.  For instance:

[source,js]
---------------
PUT my_index
{
  "mappings": {
    "my_type": {
      "properties": {
        "title":     { "type": "string" }, <1>
        "name": {
          "properties": {
            "title": { "type": "string" }, <2>
            "first": { "type": "string" },
            "last":  { "type": "string" }
          }
        }
      }
    }
  }
}
---------------
<1> This field is referred to as `title`.
<2> This field is referred to as `name.title`.

Previously, the two `title` fields in the example above could have been
confused with each other when using the short name `title`.

==== Type name prefix removed

Previously, two fields with the same name in two different types could
sometimes be disambiguated by prepending the type name.  As a side effect, it
would add a filter on the type name to the relevant query.  This feature was
ambiguous -- a type name could be confused with a field name -- and didn't
work everywhere e.g. aggregations.

Instead, fields should be specified with the full path, but without a type
name prefix.  If you wish to filter by the `_type` field, either specify the
type in the URL or add an explicit filter.

The following example query in 1.x:

[source,js]
----------------------------
GET my_index/_search
{
  "query": {
    "match": {
      "my_type.some_field": "quick brown fox"
    }
  }
}
----------------------------

would be rewritten in 2.0 as:

[source,js]
----------------------------
GET my_index/my_type/_search <1>
{
  "query": {
    "match": {
      "some_field": "quick brown fox" <2>
    }
  }
}
----------------------------
<1> The type name can be specified in the URL to act as a filter.
<2> The field name should be specified without the type prefix.

==== Field names may not contain dots

In 1.x, it was possible to create fields with dots in their name, for
instance:

[source,js]
----------------------------
PUT my_index
{
  "mappings": {
    "my_type": {
      "properties": {
        "foo.bar": { <1>
          "type": "string"
        },
        "foo": {
          "properties": {
            "bar": { <1>
              "type": "string"
            }
          }
        }
      }
    }
  }
}
----------------------------
<1> These two fields cannot be distinguished as both are referred to as `foo.bar`.

You can no longer create fields with dots in the name.

==== Type names may not start with a dot

In 1.x, Elasticsearch would issue a warning if a type name included a dot,
e.g. `my.type`.  Now that type names are no longer used to distinguish between
fields in different types, this warning has been relaxed: type names may now
contain dots, but they may not *begin* with a dot.  The only exception to this
is the special `.percolator` type.

==== Type names may not be longer than 255 characters

Mapping type names may not be longer than 255 characters.  Long type names
will continue to function on indices created before upgrade, but it will not
be possible create types with long names in new indices.

==== Types may no longer be deleted

In 1.x it was possible to delete a type mapping, along with all of the
documents of that type, using the delete mapping API.  This is no longer
supported, because remnants of the fields in the type could remain in the
index, causing corruption later on.

Instead, if you need to delete a type mapping, you should reindex to a new
index which does not contain the mapping.  If you just need to delete the
documents that belong to that type, then use the delete-by-query plugin
instead.

[[migration-meta-fields]]
==== Type meta-fields

The <<mapping-fields,meta-fields>> associated with had configuration options
removed, to make them more reliable:

* `_id` configuration can no longer be changed.  If you need to sort, use the <<mapping-uid-field,`_uid`>> field instead.
* `_type` configuration can no longer be changed.
* `_index` configuration can no longer be changed.
* `_routing` configuration is limited to marking routing as required.
* `_field_names` configuration is limited to disabling the field.
* `_size` configuration is limited to enabling the field.
* `_timestamp` configuration is limited to enabling the field, setting format and default value.
* `_boost` has been removed.
* `_analyzer` has been removed.

Importantly, *meta-fields can no longer be specified as part of the document
body.*  Instead, they must be specified in the query string parameters.  For
instance, in 1.x, the `routing` could be specified as follows:

[source,json]
-----------------------------
PUT my_index
{
  "mappings": {
    "my_type": {
      "_routing": {
        "path": "group" <1>
      },
      "properties": {
        "group": { <1>
          "type": "string"
        }
      }
    }
  }
}

PUT my_index/my_type/1 <2>
{
  "group": "foo"
}
-----------------------------
<1> This 1.x mapping tells Elasticsearch to extract the `routing` value from the `group` field in the document body.
<2> This indexing request uses a `routing` value of `foo`.

In 2.0, the routing must be specified explicitly:

[source,json]
-----------------------------
PUT my_index
{
  "mappings": {
    "my_type": {
      "_routing": {
        "required": true <1>
      },
      "properties": {
        "group": {
          "type": "string"
        }
      }
    }
  }
}

PUT my_index/my_type/1?routing=bar <2>
{
  "group": "foo"
}
-----------------------------
<1> Routing can be marked as required to ensure it is not forgotten during indexing.
<2> This indexing request uses a `routing` value of `bar`.

==== `_timestamp` and `_ttl` deprecated

The `_timestamp` and `_ttl` fields are deprecated, but will remain functional
for the remainder of the 2.x series.

Instead of the `_timestamp` field, use a normal <<date,`date`>> field and set
the value explicitly.

The current `_ttl` functionality will be replaced in a future version with a
new implementation of TTL, possibly with different semantics, and will not
depend on the `_timestamp` field.

==== Analyzer mappings

Previously, `index_analyzer` and `search_analyzer` could be set separately,
while the `analyzer` setting would set both.  The `index_analyzer` setting has
been removed in favour of just using the `analyzer` setting.

If just the `analyzer` is set, it will be used at index time and at search time.  To use a different analyzer at search time, specify both the `analyzer` and a `search_analyzer`.

The `index_analyzer`, `search_analyzer`,  and `analyzer` type-level settings
have also been removed, as it is no longer possible to select fields based on
the type name.

The `_analyzer` meta-field, which allowed setting an analyzer per document has
also been removed.  It will be ignored on older indices.

==== Date fields and Unix timestamps

Previously, `date` fields would first try to parse values as a Unix timestamp
-- milliseconds-since-the-epoch -- before trying to use their defined date
`format`.  This meant that formats like `yyyyMMdd` could never work, as values
would be interpreted as timestamps.

In 2.0, we have added two formats: `epoch_millis` and `epoch_second`.  Only
date fields that use these formats will be able to parse timestamps.

These formats cannot be used in dynamic templates, because they are
indistinguishable from long values.

==== Default date format

The default date format has changed from `date_optional_time` to
`strict_date_optional_time`, which expects a 4 digit year, and a 2 digit month
and day, (and optionally, 2 digit hour, minute, and second).

A dynamically added date field, by default, includes the `epoch_millis`
format to support timestamp parsing.  For instance:

[source,js]
-------------------------
PUT my_index/my_type/1
{
  "date_one": "2015-01-01" <1>
}
-------------------------
<1> Has `format`: `"strict_date_optional_time||epoch_millis"`.

==== `mapping.date.round_ceil` setting

The `mapping.date.round_ceil` setting for date math parsing has been removed.

[[migration-bool-fields]]
==== Boolean fields

Boolean fields used to have a string fielddata with `F` meaning `false` and `T`
meaning `true`. They have been refactored to use numeric fielddata, with `0`
for `false` and `1` for `true`. As a consequence, the format of the responses of
the following APIs changed when applied to boolean fields: `0`/`1` is returned
instead of `F`/`T`:

* <<search-request-fielddata-fields,fielddata fields>>
* <<search-request-sort,sort values>>
* <<search-aggregations-bucket-terms-aggregation,terms aggregations>>

In addition, terms aggregations use a custom formatter for boolean (like for
dates and ip addresses, which are also backed by numbers) in order to return
the user-friendly representation of boolean fields: `false`/`true`:

[source,js]
---------------
"buckets": [
  {
     "key": 0,
     "key_as_string": "false",
     "doc_count": 42
  },
  {
     "key": 1,
     "key_as_string": "true",
     "doc_count": 12
  }
]
---------------

==== `index_name` and `path` removed

The `index_name` setting was used to change the name of the Lucene field,
and the `path` setting was used on `object` fields to determine whether the
Lucene field should use the full path (including parent object fields), or
just the final `name`.

These setting have been removed as their purpose is better served with the
<<copy-to>> parameter.

==== Murmur3 Fields

Fields of type `murmur3` can no longer change `doc_values` or `index` setting.
They are always mapped as follows:

[source,js]
---------------------
{
  "type":       "murmur3",
  "index":      "no",
  "doc_values": true
}
---------------------

==== Mappings in config files not supported

The ability to specify mappings in configuration files has been removed. To
specify default mappings that apply to multiple indexes, use
<<indices-templates,index templates>> instead.

Along with this change, the following settings have been removed:

* `index.mapper.default_mapping_location`
* `index.mapper.default_percolator_mapping_location`

==== Fielddata formats

Now that doc values are the default for fielddata, specialized in-memory
formats have become an esoteric option. These fielddata formats have been removed:

* `fst` on string fields
* `compressed` on geo points

The default fielddata format will be used instead.

==== Posting and doc-values codecs

It is no longer possible to specify per-field postings and doc values formats
in the mappings. This setting will be ignored on indices created before 2.0
and will cause mapping parsing to fail on indices created on or after 2.0. For
old indices, this means that new segments will be written with the default
postings and doc values formats of the current codec.

It is still possible to change the whole codec by using the `index.codec`
setting. Please however note that using a non-default codec is discouraged as
it could prevent future versions of Elasticsearch from being able to read the
index.

==== Compress and compress threshold

The `compress` and `compress_threshold` options have been removed from the
`_source` field and fields of type `binary`.  These fields are compressed by
default.  If you would like to increase compression levels, use the new
<<index-codec,`index.codec: best_compression`>> setting instead.

==== position_offset_gap

The `position_offset_gap` option is renamed to 'position_increment_gap'. This was
done to clear away the confusion. Elasticsearch's 'position_increment_gap' now is
mapped directly to Lucene's 'position_increment_gap'

The default `position_increment_gap` is now 100. Indexes created in Elasticsearch
2.0.0 will default to using 100 and indexes created before that will continue
to use the old default of 0. This was done to prevent phrase queries from
matching across different values of the same term unexpectedly. Specifically,
100 was chosen to cause phrase queries with slops up to 99 to match only within
a single value of a field.

==== copy_to and multi fields

A <<copy-to,copy_to>> within a <<multi-fields,multi field>> is ignored from version 2.0 on. With any version after
2.1 or 2.0.1 creating a mapping that has a copy_to within a multi field will result 
in an exception.


