Question

Mongo驱动程序版本：2.2.4.26

我有以下查询执行一些聚合。如果我从Where子句中删除Contains谓词，查询将成功执行。

我希望在将数据实现到客户端内存之前减少并执行服务器上的聚合。我遇到的问题是当我在Where子句中使用Contains时，我得到以下异常：

$ project或$ group不支持Sum（{document} {ForecastQuantity}）。

如果可能的话，我宁愿继续使用linq实现而不是本机：

public class Forecast
{
    public int MarkdownGroupId { get; set; }
    public List<ForecastData> ForecastArray { get; set; }
...
}

public class ForecastData
{
    public int MarkdownNumber { get; set; }
    public double ForecastQuantity { get; set; }
...
}

public class Flat
{
    public int MarkdownGroupId { get; set; }
    public int MarkdownNumber { get; set; }
    public double SalesQuantity { get; set; }

...
}

public class FlatProjection
{
    public int MarkdownGroupId { get; set; }
    public int MarkdownNumber { get; set; }
    public double SalesQuantity { get; set; }

...
}

int[] groupIds = new int[]{ 1,2,3 };
var forecastProductDay = _mdb.GetCollection<Forecast>(collectionName);

        var forecastProductProjections = forecastProductDay
            .AsQueryable()
            .Where(x => groupIds.Contains(x.MarkdownGroupId))
            .SelectMany(x => x.ForecastArray, (x, fa) => new Flat        
            {
                MarkdownGroupId = x.MarkdownGroupId,
                MarkdownNumber = fa.MarkdownNumber,
                ForecastQuantity = fa.ForecastQuantity,
                ...
            })
            .GroupBy(key => new {key.MarkdownGroupId, key.MarkdownNumber})
            .Select(g => new FlatProjection
            {
                MarkdownGroupId = g.Key.MarkdownGroupId,
                MarkdownNumber = g.Key.MarkdownNumber,
                SalesQuantity = g.Sum(y => y.ForecastQuantity),
                ...
            })
            .OrderBy(x => x.MarkdownGroupId)
            .ThenBy(x => x.MarkdownNumber)
            .ToList();

Answer 1

由于驱动程序不喜欢Contains（）或Any（）。我使用PredicateBuilder动态构建了表达式。

public static class PredicateBuilder
{
    public static Expression<Func<T, bool>> True<T>() { return f => true; }
    public static Expression<Func<T, bool>> False<T>() { return f => false; }

    public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1,
                                                        Expression<Func<T, bool>> expr2)
    {
        var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
        return Expression.Lambda<Func<T, bool>>
              (Expression.OrElse(expr1.Body, invokedExpr), expr1.Parameters);
    }

    public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1,
                                                         Expression<Func<T, bool>> expr2)
    {
        var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
        return Expression.Lambda<Func<T, bool>>
              (Expression.AndAlso(expr1.Body, invokedExpr), expr1.Parameters);
    }
}

List ints = new List（）{1,2,3};

        var predicate = PredicateBuilder.False<Forecast>();
        foreach (var i in ints)
        {
            predicate = predicate.Or(x => x.MarkdownGroupId == i);
        }

var forecastProductDay = _mdb.GetCollection（collectionName）;

    var forecastProductProjections = forecastProductDay
        .AsQueryable()
        .Where(predicate.Compile())
        .SelectMany(x => x.ForecastArray, (x, fa) => new Flat        
        {
            MarkdownGroupId = x.MarkdownGroupId,
            MarkdownNumber = fa.MarkdownNumber,
            ForecastQuantity = fa.ForecastQuantity,
            ...
        })
        .GroupBy(key => new {key.MarkdownGroupId, key.MarkdownNumber})
        .Select(g => new FlatProjection
        {
            MarkdownGroupId = g.Key.MarkdownGroupId,
            MarkdownNumber = g.Key.MarkdownNumber,
            SalesQuantity = g.Sum(y => y.ForecastQuantity),
            ...
        })
        .OrderBy(x => x.MarkdownGroupId)
        .ThenBy(x => x.MarkdownNumber)
        .ToList();

C＃Driver- LINQ - Aggragate - 包含在Int []中

1 个答案: