Given an index named "addresses"
Write a query that will add a field called "full_address" to all the documents

full_address = NUMBER + <SPACE> + STREET + <SPACE> + UNIT + <SPACE> + POSTCODE

GET addresses/_search

POST addresses/_update_by_query
{
  "script": {
    "source": """
    ctx._source.full_address = ctx._source.NUMBER + ' ' + ctx._source.STREET + ' ' + ctx._source.UNIT + ' ' + ctx._source.POSTCODE;
    """,
    "lang": "painless"
  },
  "query": {
    "match_all": {}
  }
}

GET addresses/_search