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Filter search results

You can filter searches using different methods, each suited to specific scenarios. You can apply filters at the query level, using boolean query clauses and post_filter and aggregation level filters, as follows:

• Query-level filtering: Apply boolean query filter clauses to filter search hits and aggregations, such as to narrow results to specific categories or brands.
• Post-filter filtering: Use post_filter to refine search hits based on user selections while preserving all aggregation options.
• Aggregation-level filtering: Adjust specific aggregations based on selected filters without impacting other aggregations.

Query-level filtering with Boolean queries

Use a boolean query with a filter clause to apply filters to both search hits and aggregations. For example, if a shopper searches for smartphones from BrandA, a Boolean query can restrict results to only those smartphones from BrandA. The following steps guide you through query-level filtering.

1. Create an index electronics and provide the mapping using the following request:

PUT /electronics
{
  "mappings": {
    "properties": {
      "brand": { "type": "keyword" },
      "category": { "type": "keyword" },
      "price": { "type": "float" },
      "features": { "type": "keyword" }
    }
  }
}

1. Add documents to the electronics index using the following request:

PUT /electronics/_doc/1?refresh
{
  "brand": "BrandA",
  "category": "Smartphone",
  "price": 699.99,
  "features": ["5G", "Dual Camera"]
}
PUT /electronics/_doc/2?refresh
{
  "brand": "BrandA",
  "category": "Laptop",
  "price": 1199.99,
  "features": ["Touchscreen", "16GB RAM"]
}
PUT /electronics/_doc/3?refresh
{
  "brand": "BrandB",
  "category": "Smartphone",
  "price": 799.99,
  "features": ["5G", "Triple Camera"]
}

1. Apply a boolean filter query to display only smartphones from BrandA using the following request:

GET /electronics/_search
{
  "query": {
    "bool": {
      "filter": [
        { "term": { "brand": "BrandA" }},
        { "term": { "category": "Smartphone" }}
      ]
    }
  }
}

Narrowing results using post-filter while preserving aggregation visibility

Use post_filter to limit search hits while preserving all aggregation options. For example, if a shopper selects BrandA, results are filtered to show only BrandA products while maintaining the visibility of all brand options in the aggregations, as shown in the following example request:

GET /electronics/_search
{
  "query": {
    "bool": {
      "filter": { "term": { "category": "Smartphone" }}
    }
  },
  "aggs": {
    "brands": {
      "terms": { "field": "brand" }
    }
  },
  "post_filter": {
    "term": { "brand": "BrandA" }
  }
}

The result should show BrandA smartphones in the search hits and all brands in the aggregations.

Refining aggregations with aggregation-level filtering

You can use aggregation-level filtering to apply filters to specific aggregations without affecting the main aggregation to which they belong.

For example, you can use aggregation-level filtering to filter the price_ranges aggregation based on selected brands, BrandA and BrandB, without affecting the main price_ranges aggregation, as shown in the following example request. This displays price ranges relevant to the selected brands while also displaying overall price ranges for all products.

GET /electronics/_search
{
  "query": {
    "bool": {
      "filter": { "term": { "category": "Smartphone" }}
    }
  },
  "aggs": {
    "price_ranges": {
      "range": {
        "field": "price",
        "ranges": [
          { "to": 500 },
          { "from": 500, "to": 1000 },
          { "from": 1000 }
        ]
      }
    },
    "filtered_brands": {
      "filter": {
        "terms": { "brand": ["BrandA", "BrandB"] }
      },
      "aggs": {
        "price_ranges": {
          "range": {
            "field": "price",
            "ranges": [
              { "to": 500 },
              { "from": 500, "to": 1000 },
              { "from": 1000 }
            ]
          }
        }
      }
    }
  }
}