如何在ElasticSearch中按数组大小对项目进行排序? [英] How to sort items by array size in ElasticSearch?

问题描述

我有300万个具有这种结构的物品:

I have 3 millions items with this structure:

{
    "id": "some_id",
    "title": "some_title",
    "photos": [
        {...},
        {...},
        ...
    ]
}

某些商品的照片字段可能为空:

Some items may have empty photos field:

{
    "id": "some_id",
    "title": "some_title",
    "photos": []
}

我想按照片数量排序，以使没有照片的元素位于列表的末尾.

I want to sort by the number of photos to result in elements without photos were at the end of the list.

我有一个可行的解决方案，但是在300万个项目上却很慢:

I have the one working solution but it's very slow on 3 million items:

GET myitems/_search
{
   "filter": {
      ...some filters...
   },
   "sort": [
      {
          "_script": {
              "script": "_source.photos.size()",
              "type": "number",
              "order": "desc"
          }
      }
   ]
}

此查询执行55秒.如何优化此查询?

This query executes 55 seconds. How to optimize this query?

推荐答案

问题已通过Transform指令解决.现在我有一个映射:

Problem was solved with Transform directive. Now I have a mapping:

PUT /myitems/_mapping/lol
{
    "lol" : {
        "transform": {
            "lang": "groovy",
            "script": "ctx._source['has_photos'] = ctx._source['photos'].size() > 0"
        },
        "properties" : {
            ... fields ...
            "photos" : {"type": "object"},
            "has_photos": {"type": "boolean"}
            ... fields ...
        }
    }
}

现在，我可以按存在的照片对项目进行排序:

Now I can sort items by photos existence:

GET /test/_search
{
    "sort": [
        {
            "has_photos": {
               "order": "desc"
            }
        }
    ]
}

不幸的是，这将导致完全重新编制索引.

Unfortunately, this will cause full reindexation.

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