Ignore above
The ignore_above mapping parameter limits the maximum number of characters for an indexed string. If a string’s length exceeds the specified threshold, the value is stored with the document but is not indexed. This can help prevent the index from bloating with unusually long values and can ensure efficient queries.
By default, if you do not specify ignore_above, all string values will be fully indexed.
Example: Without ignore_above
Create an index with a keyword field without specifying the ignore_above parameter:
PUT /test-no-ignore
{
"mappings": {
"properties": {
"sentence": {
"type": "keyword"
}
}
}
}
Index a document with a long string value:
PUT /test-no-ignore/_doc/1
{
"sentence": "text longer than 10 characters"
}
Run a term query for the full string:
POST /test-no-ignore/_search
{
"query": {
"term": {
"sentence": "text longer than 10 characters"
}
}
}
The document is returned because the sentence field was indexed:
{
...
"hits": {
"total": {
"value": 1,
"relation": "eq"
},
"max_score": 0.13353139,
"hits": [
{
"_index": "test-no-ignore",
"_id": "1",
"_score": 0.13353139,
"_source": {
"sentence": "text longer than 10 characters"
}
}
]
}
}
Example: With ignore_above
Create an index with the ignore_above parameter set to 10 on the same field:
PUT /test-ignore
{
"mappings": {
"properties": {
"sentence": {
"type": "keyword",
"ignore_above": 10
}
}
}
}
Index the same document with the long string value:
PUT /test-ignore/_doc/1
{
"sentence": "text longer than 10 characters"
}
Run a term query for the full string:
POST /test-ignore/_search
{
"query": {
"term": {
"sentence": "text longer than 10 characters"
}
}
}
No results are returned because the string in the sentence field exceeded the ignore_above threshold and was not indexed:
{
"took": 3,
"timed_out": false,
"_shards": {
"total": 1,
"successful": 1,
"skipped": 0,
"failed": 0
},
"hits": {
"total": {
"value": 0,
"relation": "eq"
},
"max_score": null,
"hits": []
}
}
However, the document is still present, which can be confirmed using the following request:
GET test-ignore/_search
The returned hits include the document:
{
...
"hits": {
"total": {
"value": 1,
"relation": "eq"
},
"max_score": 1,
"hits": [
{
"_index": "test-ignore",
"_id": "1",
"_score": 1,
"_source": {
"sentence": "text longer than 10 characters"
}
}
]
}
}