Elasticsearch faceted search with aggregations

Elasticsearch Faceted Search

Faceted search (filters + aggregations) helps users narrow results: filters by category, price range, rating.

Aggregations for Facets

GET /products/_search
{
  "query": {
    "match": { "name": "laptop" }
  },
  "aggs": {
    "categories": {
      "terms": {
        "field": "category.keyword",
        "size": 10
      }
    },
    "price_ranges": {
      "range": {
        "field": "price",
        "ranges": [
          { "to": 500 },
          { "from": 500, "to": 1000 },
          { "from": 1000, "to": 2000 },
          { "from": 2000 }
        ]
      }
    },
    "brands": {
      "terms": {
        "field": "brand.keyword",
        "size": 20
      }
    }
  }
}

Response:

{
  "aggregations": {
    "categories": {
      "buckets": [
        { "key": "electronics", "doc_count": 45 },
        { "key": "computers", "doc_count": 38 }
      ]
    },
    "price_ranges": {
      "buckets": [
        { "to": 500, "doc_count": 12 },
        { "from": 500, "to": 1000, "doc_count": 28 }
      ]
    }
  }
}

Filter + Aggregation

GET /products/_search
{
  "query": {
    "bool": {
      "must": [
        { "match": { "name": "laptop" } }
      ],
      "filter": [
        { "term": { "category.keyword": "computers" } },
        { "range": { "price": { "gte": 500, "lte": 1500 } } }
      ]
    }
  },
  "aggs": {
    "brands": {
      "terms": { "field": "brand.keyword", "size": 20 }
    },
    "ratings": {
      "range": {
        "field": "rating",
        "ranges": [
          { "from": 4 },  // 4+ stars
          { "from": 3, "to": 4 }  // 3-4 stars
        ]
      }
    }
  },
  "size": 20,
  "from": 0
}