在Nest中创建动态范围聚合的技术求助

从客户端获取了一组带范围的POCO facets，需要将它们最终转换为AggregationDictionary，但无法掌握创建动态聚合（类型可能为RangeAggregationDescriptor）的语法，特此求助。

POCO对象定义 #

public class TypedFacets
{
    public string Name { get; set; }
    public string Field { get; set; }
    public IReadOnlyCollection<Range> RangeValues { get; set; } = new List<Range>();
    public int Size { get; set; }
}

public class Range
{
    public string Name { get; set; }
    public double? From { get; set; }
    public double? To { get; set; }
}

原Nest代码（存在问题） #

var facets = new List<TypedFacets>()
{
    new TypedFacets()
    {
        Name = "potatoRange",
        Field = "potatoRange",
        RangeValues = new List<Range>()
        {
            new Range()
            {
                From = 0,
                To = null,
                Name = "chips"
            },
            new Range()
            {
                From = 1,
                To = null,
                Name = "crisps"
            }
        }
    }
};

var aggregations = new AggregationContainerDescriptor<Template>();

facets.Where(f => f.RangeValues.Any()).ToList().ForEach(f =>
{
    var rad = new RangeAggregationDescriptor<Template>();

    f.RangeValues.ToList().ForEach(rangeValue =>
    {
        rad = rad.Ranges(rs => rs.From(rangeValue.From).To(rangeValue.To).Key(rangeValue.Name));
    });

    // 此行代码无法运行，需要修改
    aggregations.Range(f.Name, r => r
        .Field(f.Field).Ranges(rs => rad.Ranges));
});

return ((IAggregationContainer)aggregations).Aggregations;

解决方案 #

原代码的核心问题是试图直接复用已构建的RangeAggregationDescriptor的Ranges集合，而Nest的聚合配置是通过构建器委托逐步构建的，不能直接传递已有的配置结果。正确的做法是在Range方法的配置委托内部，直接遍历RangeValues逐个添加范围规则。

修正后的完整代码 #

var facets = new List<TypedFacets>()
{
    new TypedFacets()
    {
        Name = "potatoRange",
        Field = "potatoRange",
        RangeValues = new List<Range>()
        {
            new Range()
            {
                From = 0,
                To = null,
                Name = "chips"
            },
            new Range()
            {
                From = 1,
                To = null,
                Name = "crisps"
            }
        }
    }
};

var aggregationDescriptor = new AggregationContainerDescriptor<Template>();

// 遍历所有带范围的facet
foreach (var facet in facets.Where(f => f.RangeValues.Any()))
{
    aggregationDescriptor = aggregationDescriptor.Range(facet.Name, r => r
        .Field(facet.Field)
        // 直接在Ranges委托内遍历构建每个范围
        .Ranges(rs => 
        {
            foreach (var rangeValue in facet.RangeValues)
            {
                rs = rs.Range(rng => rng
                    .From(rangeValue.From)
                    .To(rangeValue.To)
                    .Key(rangeValue.Name));
            }
            return rs;
        }));
}

// 转换为AggregationDictionary返回
var aggregations = ((IAggregationContainer)aggregationDescriptor).Aggregations;
return aggregations;

简化写法（用LINQ Aggregate） #

如果想让代码更简洁，可以用LINQ的Aggregate方法替代foreach遍历：

foreach (var facet in facets.Where(f => f.RangeValues.Any()))
{
    aggregationDescriptor = aggregationDescriptor.Range(facet.Name, r => r
        .Field(facet.Field)
        .Ranges(rs => facet.RangeValues.Aggregate(rs, (current, rangeValue) => 
            current.Range(rng => rng
                .From(rangeValue.From)
                .To(rangeValue.To)
                .Key(rangeValue.Name)
            )
        )));
}

关键说明 #

1. 不需要提前创建RangeAggregationDescriptor实例，直接在Range方法的配置委托内完成所有范围规则的构建
2. 用foreach替代List.ForEach，避免不必要的集合转换，同时提升代码可读性
3. 每个范围规则通过Range()方法逐个添加，最终返回构建完成的范围配置器

内容的提问来源于stack exchange，提问作者Luke