Proper way to query documents using an 'uppercase' token filter - elasticsearch

Question

We have an ElasticSearch index with some fields that use custom analyzers. One of the analyzers includes an uppercase token filter in order to get rid of case sensitivity while making queries (e.g. we want "ball" to also match "Ball" or "BALL")
The issue here is when doing regular expressions, the pattern is matched against the term in the index which is all uppercase. So "app*" won't match "Apple" in our index, because behind the scenes its really indexed as "APPLE".
Is there a way to get this to work without doing some hacky things outside of ES?
I might play around with "query_string" instead and see if that has any different results.

Answer 1

This all depends on the type of the query you are using. If that type will use the analyzer of the field itself to analyze the input string then it should be fine.
If you are using the regexp query, this one will NOT analyze the input string, so if you pass app.* to it, it will stay the same and this is what it will user for search.
But, if you use properly the query_string query that one should work:
{
"settings": {
"analysis": {
"analyzer": {
"my": {
"type": "custom",
"tokenizer": "standard",
"filter": [
"uppercase"
]
}
}
}
},
"mappings": {
"test": {
"properties": {
"some_field": {
"type": "text",
"analyzer": "my"
}
}
}
}
}
And the query itself:
{
"query": {
"query_string": {
"query": "some_field:app*"
}
}
}
To make sure it's doing what I think it is, I always use the _validate api:
GET /_validate/query?explain&index=test
{
"query": {
"query_string": {
"query": "some_field:app*"
}
}
}
which will show what ES is doing to the input string:
"explanations": [
{
"index": "test",
"valid": true,
"explanation": "some_field:APP*"
}
]