OpenSearch/docs/reference/mapping/params/ignore-above.asciidoc

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[[ignore-above]]
=== `ignore_above`
Strings longer than the `ignore_above` setting will not be indexed or stored.
[source,js]
--------------------------------------------------
PUT my_index
{
"mappings": {
"my_type": {
"properties": {
"message": {
"type": "keyword",
"ignore_above": 20 <1>
}
}
}
}
}
PUT my_index/my_type/1 <2>
{
"message": "Syntax error"
}
PUT my_index/my_type/2 <3>
{
"message": "Syntax error with some long stacktrace"
}
GET _search <4>
{
"aggs": {
"messages": {
"terms": {
"field": "message"
}
}
}
}
--------------------------------------------------
// AUTOSENSE
<1> This field will ignore any string longer than 20 characters.
<2> This document is indexed successfully.
<3> This document will be indexed, but without indexing the `message` field.
<4> Search returns both documents, but only the first is present in the terms aggregation.
TIP: The `ignore_above` setting is allowed to have different settings for
fields of the same name in the same index. Its value can be updated on
existing fields using the <<indices-put-mapping,PUT mapping API>>.
This option is also useful for protecting against Lucene's term byte-length
limit of `32766`.
NOTE: The value for `ignore_above` is the _character count_, but Lucene counts
bytes. If you use UTF-8 text with many non-ASCII characters, you may want to
set the limit to `32766 / 3 = 10922` since UTF-8 characters may occupy at most
3 bytes.