Multi-index searching with highlighting across heterogenous types.

multi_index_elastic_search.rb

# We have a couple of indices that have been created independently.
# Now we want to search across them, with highlighting (and ideally
# suggestors as well) without breaking exisiting services.
#
# The mappings do not have consistent field names, but they have fields that can
# be semantically mapped into "title" or "body" (and some others) fields.
#
# From the size of the data, I'm told that creating a new purpose-build index is
# out of the question--even something that would duplicate data in another field
# in the same index is a stretch.
#
# Which is what lead me to look at `index_name` and `copy_to`.

PUT /restaurants
# For this type, `name` and `description` map 1:1 to `title` and `body`
PUT /restaurants/fast_food/_mapping
{
  "fast_food" : {
    "properties": {
      "name" : { "type": "string", "index_name": "title"},
      "description" : { "type": "string", "index_name": "body"}
    }
  }
}
PUT /restaurants/fast_food/1
{
  "name": "Trough King",
  "description": "French fries injected directly into your heart!"
}
PUT /restaurants/fast_food/2
{
  "name": "Charles Cheese Family Fun Fest",
  "description": "Lots and lots of cheese. Also, robotic rats wearing funny hats."
}
# For this type, we have two fields that we want to treat as `body`, so we're going to treat
# `summary` as the "main" `body` field, and `letter_from_chef` as a "secondary" one.
PUT /restaurants/fancy/_mapping
{
  "fancy" : {
    "properties": {
      "name" : { "type": "string", "index_name": "title"},
      "summary" : { "type": "string", "index_name": "body"},
      "letter_from_chef" : { "type": "string", "copy_to": "body"}
    }
  }
}
PUT /restaurants/fancy/1
{
  "name": "Chez Fromage",
  "summary": "French food masterfully cooked by some guy in a funny hat. Also, great cheese.",
  "letter_from_chef": "Bonjour! Enjoy my cheese!"
}

# This example's only here to test multi-index searching
PUT /hotels
PUT /hotels/hotel/_mapping
{
  "hotel": {
    "properties": { 
      "hotelName" : { "type": "string", "index_name": "title"},
      "hotelDescription": { "type": "string", "index_name": "body"},
      "hotelRating": {"type": "integer"}
    }
  }
}
PUT /hotels/hotel/1
{
  "hotelName": "Sleep Already",
  "hotelDescription": "Okay, I guess. Room smelled like cheese, but no rats, so can't complain, right?",
  "hotelRating": 2
}

# Check that everything looks right...
GET /restaurants,hotels/_mapping
# Note that all of the fields are returned by mapping name, not index name (which makes sense).
GET /restaurants,hotels/_search
{"query": {"match_all": {}}}

# Let's make sure our existing hotel search still works...
GET /hotels/_search
{
  "highlight": {
    "fields": {
      "hotelName": {},
      "hotelDescription": {}
    }
  },
  "query": {
    "filtered": {
      "query": {
        "multi_match": {
          "query": "cheese",
            "fields": [
              "hotelName^2",
              "hotelDescription"
            ]
        }
      },
      "filter": {
        "range": {
          "hotelRating": { "gte": 2}
        }
      }
    }
  }
}
# Good. As expected, searching by mapping names still works.

# A highlighted multi-index search:
GET /restaurants,hotels/_search
{
  "highlight": {
    "fields": {
      "title": {},
      "body": {
        "number_of_fragments": 3
      }
    }
  },
  "query": {
    "multi_match": {
      "query": "cheese",
      "fields": [
        "title^2",
        "body"
      ]
    }
  }
}
# Pretty good: it queries our fields by "index_name" and highlights them.
# However, restaurant/fancy/1's body highlight only contains a match from `summary`.

# Maybe the copy_to isn't working?
GET /restaurants,hotels/_search
{
  "highlight": {
    "fields": {
      "title": {},
      "body": {
        "number_of_fragments": 3
      }
    }
  },
  "query": {
    "multi_match": {
      "query": "bonjour",
      "fields": [
        "title^2",
        "body"
      ]
    }
  }
}
# Nope, it matched on the `letter_from_chef` field, but no highlighting...

# Can we restrict the source fields by index_name?
GET /restaurants,hotels/_search
{
  "highlight": {
    "fields": {
      "title": {},
      "body": {
        "number_of_fragments": 3
      }
    }
  },
  "query": {
    "multi_match": {
      "query": "cheese",
      "fields": [
        "title^2",
        "body"
      ]
    }
  },
  "_source": ["title", "body"]
}
# No. Neither the "copy_to" or "index_name" fields show up.

# Okay, so highlighting doesn't work as I thought it would here. How about suggestors?
# Suggestors can use copied fields
GET /restaurants,hotels/_search
{
  "highlight": {
    "fields": {
      "title": {},
      "body": {
        "number_of_fragments": 3
      }
    }
  },
  "query": {
    "multi_match": {
      "query": "eat my ches",
      "fields": [
        "title^2",
        "body"
      ]
    }
  },
  "suggest": {
    "text": "eat my ches",
    "my-suggestor": {
      "phrase": {
        "size": 3,
        "field": "body"      
      }
    }
  }
}
# Interesting. The suggestor works fine with a copy_to field. (Not shown: works with index_name ones too. Try 'funn hat').