在弹性搜索中检索字段名称表单值

Question

这是我想要索引和搜索的Json文档

{
    "BookName":"Book1",
    "ISBN":"978-3-16-148410-0",
    "PageCount":"504",
    "Chapters":{
        "Chapter1":"Chapter_Content",
        "Chapter2":"Chapter_Content",
        "Chapter3":"Chapter_Content",
        "Chapter4":"Chapter_Content",
        "Chapter5":"Chapter_Content",
        "Chapter6":"Chapter_Content",
        ...
        "ChapterN":"Chapter_Content"
    }
}

{
    "BookName":"Book2",
    "ISBN":"548-1-13-344410-1",
    "PageCount":"504",
    "Chapters":{
        "Chapter1":"Chapter_Content",
        "Chapter2":"Chapter_Content",
        "Chapter3":"Chapter_Content",
        ...
        "ChapterN":"Chapter_Content"

    }
}

我想从这些文档中检索章节号，就像我搜索任何章节内容一样它应该返回ChapterName（第1章，第2章......）

这是一个例子：

{
    "BookName":"Book1",
    "ISBN":"978-3-16-148410-0",
    "PageCount":"504",
    "Chapters":{
        "Chapter1":"This textbook was written with two primary objectives. The first is to introduce...",
        "Chapter2":"C is a general-purpose programming language, and is used for writing programs in many different domains, such as ...",
        "Chapter3":"The following program is the traditional first program presented in introductory C courses and textbooks...",
        "Chapter4":"The following program produces identical output to the previous example. It shows ...",
        "Chapter5":"This text is organised in a sequential fashion—from fundamentals to higher-level constructs and software design issues. The core language is covered in Chapters 2–5 and...",
        "Chapter6":"Identifiers (i.e., variable names, function names, etc) are made up of letters and digits, and are case-sensitive. The first ...",
        ...
        "ChapterN":"Other Content..."
    }
}

现在在json上面如果我搜索传统，它应该返回第3章 或者，如果我搜索区分大小写，则应返回第6章。

- 示例结束 -

我尝试过突出显示方法，但使用突出显示我必须存储数据，这会增加索引的大小，根据我的映射，我已从源中排除了章节字段。

有没有更好的解决方案？

提前致谢！