Wildcard/regexp query with asterix chacter

Question

I'm new to elasticsearch. I would write a query, that matches a document with the following attribute:

description: 20*40x555

I want the query matches with the following inputs:

• 20X40X555
• 20*40*555
• 20x40x555
• the combination of these

I tired the wildcard, and the regex query also. If the document's attribute does not contains any asterix characters the query works fine, but when the description attribute contains an * character it does not find.

I tried with the following queries:

with wildcard:

{
  "query": {
    "bool": {
      "must": [
        {
          "wildcard": {
            "short_description": "*20?40?555*"
          }
        }
      ]
    }
  }
}

with regexp:

{
  "query": {
    "bool": {
      "must": [
        {
          "regexp": {
            "short_description": ".*20.*40.*555.*"
          }
        }
      ]
    }
  }
}

When the short attribute is ex 20x40x555 both of these working, but if I change the value to 20*40x555 it does not returns the document unfortunately.

How can I achieve to get results when the value of the sort_description is eg. 20*40x555 ? Thanks!

Answer 1

Assuming that you are using standard analyzer to index the "*" is no longer present in the index. The text 20*40x555 is indexed as two tokens 20 and 40x555. The simplest way to make * interchangeable with x is to replace it with x during the indexing operations by using patter_replace filter. Here is a simple example that illustrates this idea:

DELETE test

PUT test
{
  "settings": {
    "analysis": {
      "char_filter": {
        "asterisk_to_x": {
          "type": "pattern_replace",
          "pattern": "(\\S)\\*(\\S)",
          "replacement": "$1x$2"
        }
      },
      "analyzer": {
        "custom_analyzer": {
          "tokenizer": "keyword",
          "char_filter": ["asterisk_to_x"],
          "filter": ["lowercase"]
        }
      }
    }
  },
  "mappings": {
    "properties": {
      "short_description": {
        "type": "text", 
        "analyzer": "custom_analyzer"
      }
    }
  }
}

POST test/_bulk?refresh
{ "index": { "_id": "1" } }
{"short_description":"20x40*555"}


POST test/_search
{
  "query": {
    "bool": {
      "must": [
        {
          "match": {
            "short_description": "20X40X555"
          }
        }
      ]
    }
  }
}