Run query by regex on _id field in Elasticsearch - regex

Question

I'm trying to run a regex query in Elastic search based on a field called _id, but I'm getting this error:
Can only use wildcard queries on keyword and text fields - not on
[_id] which is of type [_id]
I've tried regexp:
{
"query": {
"regexp": {
"_id": {
"value": "test-product-all-user_.*",
"flags" : "ALL",
"max_determinized_states": 10000,
"rewrite": "constant_score"
}
}
}
}
and wildcard:
{
"query": {
"wildcard": {
"_id": {
"value": "test-product-all-user_.*",
"boost": 1.0,
"rewrite": "constant_score"
}
}
}
}
But both threw the same error.
This is the complete error just in case:
{ "error": {
"root_cause": [
{
"type": "query_shard_exception",
"reason": "Can only use wildcard queries on keyword and text fields - not on [_id] which is of type [_id]",
"index_uuid": "Cg0zrr6dRZeHJ8Jmvh5HMg",
"index": "explore_segments_v3"
}
],
"type": "search_phase_execution_exception",
"reason": "all shards failed",
"phase": "query",
"grouped": true,
"failed_shards": [
{
"shard": 0,
"index": "explore_segments_v3",
"node": "-ecTRBmnS2OgjHrrq6GCOw",
"reason": {
"type": "query_shard_exception",
"reason": "Can only use wildcard queries on keyword and text fields - not on [_id] which is of type [_id]",
"index_uuid": "Cg0zrr6dRZeHJ8Jmvh5HMg",
"index": "explore_segments_v3"
}
}
] }, "status": 400 }

Answer 1

_id is a special kind of feild in Elasticsearch , It's not really an indexed field like other text fields, it's actually "generated" based on the UID of the document.
You can refer to this link for more information https://www.elastic.co/guide/en/elasticsearch/reference/current/mapping-id-field.html
As per the documentation it only supports limited type of queries (term, terms, match, query_string, simple_query_string), and if you want to do more advanced text search like wildcard or regexp you will need to index the ID into an actual text field on the document itself.