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Custom _all Fieldsedit
In Metadata: _all Field, we explained that the special _all field indexes the values
from all other fields as one big string.
Having all fields indexed into one
field is not terribly flexible, though. It would be nice to have one custom
_all field for the person’s name, and another custom _all field for the
address.
Elasticsearch provides us with this functionality via the copy_to parameter
in a field
mapping:
PUT /my_index
{
"mappings": {
"person": {
"properties": {
"first_name": {
"type": "string",
"copy_to": "full_name" 
},
"last_name": {
"type": "string",
"copy_to": "full_name" 
},
"full_name": {
"type": "string"
}
}
}
}
}
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The values in the |
With this mapping in place, we can query the first_name field for first
names, the last_name field for last name, or the full_name field for first
and last names.
Mappings of the first_name and last_name fields have no bearing
on how the full_name field is indexed. The full_name field copies the
string values from the other two fields, then indexes them according to the
mapping of the full_name field only.
The copy_to setting will not work on a multi-field. If you attempt
to configure your mapping this way, Elasticsearch will throw an exception.
Why? Multi-fields are simply indexing the "main" field a different way; they don’t
have their own source. Which means there is no source to copy_to a different
field.
You can easily copy_to the "main" field to achieve the same effect:
PUT /my_index
{
"mappings": {
"person": {
"properties": {
"first_name": {
"type": "string",
"copy_to": "full_name",
"fields": {
"raw": {
"type": "string",
"index": "not_analyzed"
}
}
},
"full_name": {
"type": "string"
}
}
}
}
}
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