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折叠混合查询结果

于 3.1 版本引入

collapse 参数允许您按字段对结果进行分组，只返回每个唯一字段值的最高得分文档。这在您希望避免搜索结果中出现重复项时非常有用。您进行折叠的字段必须是 keyword 类型或数字类型。返回结果的数量仍受查询中 size 参数的限制。

collapse 参数与其他混合查询搜索选项（如排序、解释和分页）兼容，使用其标准语法。

在混合查询中使用 collapse 时，请注意以下事项：

  • 不支持内部匹配项（Inner hits）。
  • 处理大型结果集时，性能可能会受到影响。
  • 聚合在折叠前的结果上运行，而非最终输出。
  • 分页行为变更：由于 collapse 减少了结果总数，它会影响结果在页面间的分布方式。要检索更多结果，请考虑增加分页深度。
  • 结果可能与 collapse 响应处理器 返回的结果不同，后者在查询执行后应用折叠逻辑。

示例

以下示例演示了如何折叠混合查询结果。

创建索引

PUT /bakery-items
{
  "mappings": {
    "properties": {
      "item": {
        "type": "keyword"
      },
      "category": {
        "type": "keyword"
      },
      "price": {
        "type": "float"
      },
      "baked_date": {
        "type": "date"
      }
    }
  }
}

将文档摄取到索引中

POST /bakery-items/_bulk
{ "index": {} }
{ "item": "Chocolate Cake", "category": "cakes", "price": 15, "baked_date": "2023-07-01T00:00:00Z" }
{ "index": {} }
{ "item": "Chocolate Cake", "category": "cakes", "price": 18, "baked_date": "2023-07-04T00:00:00Z" }
{ "index": {} }
{ "item": "Vanilla Cake", "category": "cakes", "price": 12, "baked_date": "2023-07-02T00:00:00Z" }
{ "index": {} }
{ "item": "Vanilla Cake", "category": "cakes", "price": 16, "baked_date": "2023-07-03T00:00:00Z" }
{ "index": {} }
{ "item": "Vanilla Cake", "category": "cakes", "price": 17, "baked_date": "2023-07-09T00:00:00Z" }

创建一个搜索管道。此示例使用 min_max 归一化技术。

PUT /_search/pipeline/norm-pipeline
{
  "description": "Normalization processor for hybrid search",
  "phase_results_processors": [
    {
      "normalization-processor": {
        "normalization": {
          "technique": "min_max"
        },
        "combination": {
          "technique": "arithmetic_mean"
        }
      }
    }
  ]
}

搜索索引，按 item 字段对搜索结果进行分组。

GET /bakery-items/_search?search_pipeline=norm-pipeline
{
  "query": {
    "hybrid": {
      "queries": [
        {
          "match": {
            "item": "Chocolate Cake"
          }
        },
        {
          "bool": {
            "must": {
              "match": {
                "category": "cakes"
              }
            }
          }
        }
      ]
    }
  },
  "collapse": {
    "field": "item"
  }
}

响应返回折叠的搜索结果。

"hits": {
    "total": {
      "value": 5,
      "relation": "eq"
    },
    "max_score": 1.0,
    "hits": [
      {
        "_index": "bakery-items",
        "_id": "wBRPZZcB49c_2-1rYmO7",
        "_score": 1.0,
        "_source": {
          "item": "Chocolate Cake",
          "category": "cakes",
          "price": 15,
          "baked_date": "2023-07-01T00:00:00Z"
        },
        "fields": {
          "item": [
            "Chocolate Cake"
          ]
        }
      },
      {
        "_index": "bakery-items",
        "_id": "whRPZZcB49c_2-1rYmO7",
        "_score": 0.5005,
        "_source": {
          "item": "Vanilla Cake",
          "category": "cakes",
          "price": 12,
          "baked_date": "2023-07-02T00:00:00Z"
        },
        "fields": {
          "item": [
            "Vanilla Cake"
          ]
        }
      }
    ]
  }

折叠并排序结果

要折叠并排序混合查询结果，请在查询中提供 collapse 和 sort 参数。

GET /bakery-items/_search?search_pipeline=norm-pipeline
{
  "query": {
    "hybrid": {
      "queries": [
        {
          "match": {
                "item": "Chocolate Cake"
          }
        },
        {
          "bool": {
                "must": {
                    "match": {
                        "category": "cakes"
                    }
                }
          }
        }
      ]
    }
  },
  "collapse": {
    "field": "item"
  },
  "sort": "price"
}

有关混合查询中排序的更多信息，请参阅 在混合查询中使用排序。

在响应中，文档按最低价格排序。

"hits": {
    "total": {
      "value": 5,
      "relation": "eq"
    },
    "max_score": null,
    "hits": [
      {
        "_index": "bakery-items",
        "_id": "whRPZZcB49c_2-1rYmO7",
        "_score": null,
        "_source": {
          "item": "Vanilla Cake",
          "category": "cakes",
          "price": 12,
          "baked_date": "2023-07-02T00:00:00Z"
        },
        "fields": {
          "item": [
            "Vanilla Cake"
          ]
        },
        "sort": [
          12.0
        ]
      },
      {
        "_index": "bakery-items",
        "_id": "wBRPZZcB49c_2-1rYmO7",
        "_score": null,
        "_source": {
          "item": "Chocolate Cake",
          "category": "cakes",
          "price": 15,
          "baked_date": "2023-07-01T00:00:00Z"
        },
        "fields": {
          "item": [
            "Chocolate Cake"
          ]
        },
        "sort": [
          15.0
        ]
      }
    ]
  }

折叠并解释

在折叠搜索结果时，您可以提供 explain 查询参数。

GET /bakery-items/_search?search_pipeline=norm-pipeline&explain=true
{
  "query": {
    "hybrid": {
      "queries": [
        {
          "match": {
                "item": "Chocolate Cake"
          }
        },
        {
          "bool": {
                "must": {
                    "match": {
                        "category": "cakes"
                    }
                }
          }
        }
      ]
    }
  },
  "collapse": {
    "field": "item"
  }
}

响应包含每个搜索结果评分过程的详细信息。

"hits": {
        "total": {
            "value": 5,
            "relation": "eq"
        },
        "max_score": 1.0,
        "hits": [
            {
                "_shard": "[bakery-items][0]",
                "_node": "Jlu8P9EaQCy3C1BxaFMa_g",
                "_index": "bakery-items",
                "_id": "3ZILepcBheX09_dPt8TD",
                "_score": 1.0,
                "_source": {
                    "item": "Chocolate Cake",
                    "category": "cakes",
                    "price": 15,
                    "baked_date": "2023-07-01T00:00:00Z"
                },
                "fields": {
                    "item": [
                        "Chocolate Cake"
                    ]
                },
                "_explanation": {
                    "value": 1.0,
                    "description": "combined score of:",
                    "details": [
                        {
                            "value": 1.0,
                            "description": "ConstantScore(item:Chocolate Cake)",
                            "details": []
                        },
                        {
                            "value": 1.0,
                            "description": "ConstantScore(category:cakes)",
                            "details": []
                        }
                    ]
                }
            },
            {
                "_shard": "[bakery-items][0]",
                "_node": "Jlu8P9EaQCy3C1BxaFMa_g",
                "_index": "bakery-items",
                "_id": "35ILepcBheX09_dPt8TD",
                "_score": 0.5005,
                "_source": {
                    "item": "Vanilla Cake",
                    "category": "cakes",
                    "price": 12,
                    "baked_date": "2023-07-02T00:00:00Z"
                },
                "fields": {
                    "item": [
                        "Vanilla Cake"
                    ]
                },
                "_explanation": {
                    "value": 1.0,
                    "description": "combined score of:",
                    "details": [
                        {
                            "value": 0.0,
                            "description": "ConstantScore(item:Chocolate Cake) doesn't match id 2",
                            "details": []
                        },
                        {
                            "value": 1.0,
                            "description": "ConstantScore(category:cakes)",
                            "details": []
                        }
                    ]
                }
            }
        ]
    }

有关在混合查询中使用 explain 的更多信息，请参阅 混合搜索解释。

折叠和分页

您可以通过提供 from 和 size 参数来对折叠后的结果进行分页。有关混合查询中分页的更多信息，请参阅 对混合查询结果进行分页。有关 from 和 size 的更多信息，请参阅 from 和 size 参数。

对于此示例，创建以下索引：

PUT /bakery-items-pagination
{
    "settings": {
         "index.number_of_shards": 3
    },
  "mappings": {
    "properties": {
      "item": {
        "type": "keyword"
      },
      "category": {
        "type": "keyword"
      },
      "price": {
        "type": "float"
      },
      "baked_date": {
        "type": "date"
      }
    }
  }
}

将以下文档摄取到索引中：

POST /bakery-items-pagination/_bulk
{ "index": {} }
{ "item": "Chocolate Cake", "category": "cakes", "price": 15, "baked_date": "2023-07-01T00:00:00Z" }
{ "index": {} }
{ "item": "Chocolate Cake", "category": "cakes", "price": 18, "baked_date": "2023-07-02T00:00:00Z" }
{ "index": {} }
{ "item": "Vanilla Cake", "category": "cakes", "price": 12, "baked_date": "2023-07-02T00:00:00Z" }
{ "index": {} }
{ "item": "Vanilla Cake", "category": "cakes", "price": 11, "baked_date": "2023-07-04T00:00:00Z" }
{ "index": {} }
{ "item": "Ice Cream Cake", "category": "cakes", "price": 23, "baked_date": "2023-07-09T00:00:00Z" }
{ "index": {} }
{ "item": "Ice Cream Cake", "category": "cakes", "price": 22, "baked_date": "2023-07-10T00:00:00Z" }
{ "index": {} }
{ "item": "Carrot Cake", "category": "cakes", "price": 24, "baked_date": "2023-07-09T00:00:00Z" }
{ "index": {} }
{ "item": "Carrot Cake", "category": "cakes", "price": 26, "baked_date": "2023-07-21T00:00:00Z" }
{ "index": {} }
{ "item": "Red Velvet Cake", "category": "cakes", "price": 25, "baked_date": "2023-07-09T00:00:00Z" }
{ "index": {} }
{ "item": "Red Velvet Cake", "category": "cakes", "price": 29, "baked_date": "2023-07-30T00:00:00Z" }
{ "index": {} }
{ "item": "Cheesecake", "category": "cakes", "price": 27. "baked_date": "2023-07-09T00:00:00Z" }
{ "index": {} }
{ "item": "Cheesecake", "category": "cakes", "price": 34. "baked_date": "2023-07-21T00:00:00Z" }
{ "index": {} }
{ "item": "Coffee Cake", "category": "cakes", "price": 42, "baked_date": "2023-07-09T00:00:00Z" }
{ "index": {} }
{ "item": "Coffee Cake", "category": "cakes", "price": 41, "baked_date": "2023-07-05T00:00:00Z" }
{ "index": {} }
{ "item": "Cocunut Cake", "category": "cakes", "price": 23, "baked_date": "2023-07-09T00:00:00Z" }
{ "index": {} }
{ "item": "Cocunut Cake", "category": "cakes", "price": 32, "baked_date": "2023-07-12T00:00:00Z" }
// Additional documents omitted for brevity

运行一个 hybrid 查询，通过指定 from 和 size 参数来对结果进行分页。在以下示例中，查询请求从第 6 个位置开始的两个结果（from: 5, size: 2）。分页深度设置为限制每个分片最多返回 10 个文档。检索到结果后，应用 collapse 参数以按 item 字段对它们进行分组。

GET /bakery-items-pagination/_search?search_pipeline=norm-pipeline
{
  "query": {
    "hybrid": {
      "pagination_depth": 10,
      "queries": [
        {
          "match": {
                "item": "Chocolate Cake"
          }
        },
        {
          "bool": {
                "must": {
                    "match": {
                        "category": "cakes"
                    }
                }
          }
        }
      ]
    }
  },
  "from": 5,
  "size": 2,
  "collapse": {
    "field": "item"
  }
}


"hits": {
        "total": {
            "value": 70,
            "relation": "eq"
        },
        "max_score": 1.0,
        "hits": [
            {
                "_index": "bakery-items-pagination",
                "_id": "gDayepcBIkxlgFKYda0p",
                "_score": 0.5005,
                "_source": {
                    "item": "Red Velvet Cake",
                    "category": "cakes",
                    "price": 29,
                    "baked_date": "2023-07-30T00:00:00Z"
                },
                "fields": {
                    "item": [
                        "Red Velvet Cake"
                    ]
                }
            },
            {
                "_index": "bakery-items-pagination",
                "_id": "aTayepcBIkxlgFKYca15",
                "_score": 0.5005,
                "_source": {
                    "item": "Vanilla Cake",
                    "category": "cakes",
                    "price": 12,
                    "baked_date": "2023-07-02T00:00:00Z"
                },
                "fields": {
                    "item": [
                        "Vanilla Cake"
                    ]
                }
            }
        ]
    }
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