How to write a simple regexp query using elasticsearch in python?

Question

I am trying to write a simple regexp query using elasticsearch in python that just won't work. Can anybody tell me where I'm going wrong ?

result = es.search(index="my-index", body={"query": {"regexp": {"Name": "Vi.*" }}})

The indexed document is a list of names with my name also in it (Vitthal Bhandari). The above query always yields empty results when it should return my name instead. The document is properly indexed and other queries work just fine. For instance a match query gives the required result.

result = es.search(index="my-index", body={"query": {"match": {"Name": "Vitthal" }}})

What is the problem with the regexp query that I'm writing that it won't give any result? Any suggestions?

**EDIT : ** The "Name" mapping is given below :

"Name" : {
          "type" : "text",
          "fields" : {
            "keyword" : {
              "type" : "keyword",
              "ignore_above" : 256
            }
          }
        },

Answer 1

As per your mapping

"Name" : {
          "type" : "text",
          "fields" : {
            "keyword" : {
              "type" : "keyword",
              "ignore_above" : 256
            }
          }
        }

You have default analyzer

To make it work:

{"query": {"regexp": {"Name": "vi.*" }}}

Use lower case.

Reason for Vi.* not working:

regexp is a term query. It is not a full text search query.

Unlike full-text queries, term-level queries do not analyze search terms. Instead, term-level queries match the exact terms stored in a field.

So, it expects terms starting with Vi in the index which is not true as it is analysed and stored as vi..

Reference