Kibana Regular expression search

GET /_search
{
    "query": {
        "regexp": {
            "user": {
                "value": "k.*y",
                "flags" : "ALL",
                "max_determinized_states": 10000,
                "rewrite": "constant_score"
            }
        }
    }
}

More details on here

I'm not sure offhand why that regex query wouldn't be working but I believe Kibana is using Elasticsearch's query string query documented here so for instance you could do a phrase query (documented in the link) by putting your search in double quotes and it would look for the word "foo" followed by "bar". This would perform better too since you would do this on your analyzed field (my_field) where it has tokenized each word to perform fast lookups. So you search in Kibana would be:

my_field: "FOO BAR"

Update:

Looks like this is an annoying quirk of Kibana (probably for backwards compatability reasons). Anyway, this isn't matching for you because you're searching against a non-analyzed field and apparently Kibana by default is lowercasing the search therefore it won't match the the non-analyzed uppercase "FOO". You can configure this in Kibana advanced settings mentioned here, specifically by setting the configuration option "lowercase_expanded_terms" to false.

Kibana’s standard query language is based on Lucene query syntax.

And the default analyzer will tokenize the text to different words: [MY, FOO, WORD, BAR, EXAMPLE]

Instead of using regex match, you can try the following search string in Kibana:

my_field: FOO AND my_field: BAR

And if your "my_field" data looks like "MYFOOWORDBAREXAMPLE",which can not be tokenized, you should use the query string:

my_field: *FOO*BAR*