Add aggregations to Search-Hybrid search section

_search-plugins/hybrid-search.md

@@ -297,8 +297,8 @@ The response contains the matching documents:
 ```
 {% include copy-curl.html %}
 
-### Hybrid search with post-filtering
-Introduced 2.13
+## Hybrid search with post-filtering
+**Introduced 2.13**
 {: .label .label-purple }
 
 You can perform post-filtering on hybrid search results by providing the `post_filter` parameter in your query.
@@ -374,3 +374,199 @@ Compare the results to the results without post-filtering in the [preceding exam
   }
 }
 ```
+
+
+## Combining hybrid search and aggregations
+**Introduced 2.13**
+{: .label .label-purple }
+
+You can enhance search results by combining a hybrid query clause with any aggregation that OpenSearch supports. Aggregations allow you to use OpenSearch as an analytics engine. For more information about aggregations, see [Aggregations]({{site.url}}{{site.baseurl}}/aggregations/).
+
+Most aggregations are performed on the subset of documents that is returned by a hybrid query. The only aggregation that operates on all documents is the [`global`]({{site.url}}{{site.baseurl}}/aggregations/bucket/global/) aggregation.
+
+To use aggregations with a hybrid query, first create an index. Aggregations are typically used on fields of special types, like `keyword` or `integer`. The following example creates an index with several such fields:
+
+```json
+PUT /my-nlp-index
+{
+  "settings": {
+    "number_of_shards": 2
+  },
+  "mappings": {
+    "properties": {
+      "doc_index": {
+        "type": "integer"
+      },
+      "doc_keyword": {
+        "type": "keyword"
+      },
+      "category": {
+        "type": "keyword"
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+The following request ingests six documents into your new index:
+
+```json
+POST /_bulk
+{ "index": { "_index": "my-nlp-index" } }
+{ "category": "permission", "doc_keyword": "workable", "doc_index": 4976, "doc_price": 100}
+{ "index": { "_index": "my-nlp-index" } }
+{ "category": "sister", "doc_keyword": "angry", "doc_index": 2231, "doc_price": 200 }
+{ "index": { "_index": "my-nlp-index" } }
+{ "category": "hair", "doc_keyword": "likeable", "doc_price": 25 }
+{ "index": { "_index": "my-nlp-index" } }
+{ "category": "editor", "doc_index": 9871, "doc_price": 30 }
+{ "index": { "_index": "my-nlp-index" } }
+{ "category": "statement", "doc_keyword": "entire", "doc_index": 8242, "doc_price": 350  } 
+{ "index": { "_index": "my-nlp-index" } }
+{ "category": "statement", "doc_keyword": "idea", "doc_index": 5212, "doc_price": 200  } 
+{ "index": { "_index": "index-test" } }
+{ "category": "editor", "doc_keyword": "bubble", "doc_index": 1298, "doc_price": 130 } 
+{ "index": { "_index": "index-test" } }
+{ "category": "editor", "doc_keyword": "bubble", "doc_index": 521, "doc_price": 75  } 
+```
+{% include copy-curl.html %}
+
+Now you can combine a hybrid query clause with a `min` aggregation:
+
+```json
+GET /my-nlp-index/_search?search_pipeline=nlp-search-pipeline
+{
+  "query": {
+    "hybrid": {
+      "queries": [
+        {
+          "term": {
+            "category": "permission"
+          }
+        },
+        {
+          "bool": {
+            "should": [
+              {
+                "term": {
+                  "category": "editor"
+                }
+              },
+              {
+                "term": {
+                  "category": "statement"
+                }
+              }
+            ]
+          }
+        }
+      ]
+    }
+  },
+  "aggs": {
+    "total_price": {
+      "sum": {
+        "field": "doc_price"
+      }
+    },
+    "keywords": {
+      "terms": {
+        "field": "doc_keyword",
+        "size": 10
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+The response contains the matching documents and the aggregation results: 
+
+```json
+{
+  "took": 9,
+  "timed_out": false,
+  "_shards": {
+    "total": 2,
+    "successful": 2,
+    "skipped": 0,
+    "failed": 0
+  },
+  "hits": {
+    "total": {
+      "value": 4,
+      "relation": "eq"
+    },
+    "max_score": 0.5,
+    "hits": [
+      {
+        "_index": "my-nlp-index",
+        "_id": "mHRPNY4BlN82W_Ar9UMY",
+        "_score": 0.5,
+        "_source": {
+          "doc_price": 100,
+          "doc_index": 4976,
+          "doc_keyword": "workable",
+          "category": "permission"
+        }
+      },
+      {
+        "_index": "my-nlp-index",
+        "_id": "m3RPNY4BlN82W_Ar9UMY",
+        "_score": 0.5,
+        "_source": {
+          "doc_price": 30,
+          "doc_index": 9871,
+          "category": "editor"
+        }
+      },
+      {
+        "_index": "my-nlp-index",
+        "_id": "nXRPNY4BlN82W_Ar9UMY",
+        "_score": 0.5,
+        "_source": {
+          "doc_price": 200,
+          "doc_index": 5212,
+          "doc_keyword": "idea",
+          "category": "statement"
+        }
+      },
+      {
+        "_index": "my-nlp-index",
+        "_id": "nHRPNY4BlN82W_Ar9UMY",
+        "_score": 0.5,
+        "_source": {
+          "doc_price": 350,
+          "doc_index": 8242,
+          "doc_keyword": "entire",
+          "category": "statement"
+        }
+      }
+    ]
+  },
+  "aggregations": {
+    "total_price": {
+      "value": 680
+    },
+    "doc_keywords": {
+      "doc_count_error_upper_bound": 0,
+      "sum_other_doc_count": 0,
+      "buckets": [
+        {
+          "key": "entire",
+          "doc_count": 1
+        },
+        {
+          "key": "idea",
+          "doc_count": 1
+        },
+        {
+          "key": "workable",
+          "doc_count": 1
+        }
+      ]
+    }
+  }
+}
+```