EFCore 2.2 GroupBy Sum and DateDiff

Question

I'm trying to translate the following SQL in to an EF Core query and I'm getting warnings that GroupBy and Sum will be evaluated locally. Is there anyway currently to write this that it will fully translate to SQL?

SELECT UserId, ST.StatusId, SUM(DATEDIFF(MINUTE, StartDate, ISNULL(EndDate,GETDATE()))) AS Time
FROM StatusTransaction ST
WHERE
    TeamManagerId = 1
    AND StartDate >= N'01-01-2019'
    AND ISNULL(EndDate,GETDATE()) <= N'01-02-2019'
GROUP BY UserId, ST.StatusId
ORDER BY UserId

And these are the EF queries I've used:

var efFunction = await context
    .Where(st => st.TeamManagerId == tmId && st.StartDate >= dateFrom && (st.EndDate ?? DateTime.Now) <= dateTo)
    .GroupBy(st => new { st.UserId, st.StatusId })
    .Select(g => new
        {
            g.Key.UserId,
            g.Key.StatusId,
            Time = g.Sum(st => Microsoft.EntityFrameworkCore.EF.Functions.DateDiffMinute(st.StartDate, st.EndDate)) // null check not done on end date - (st.EndDate ?? DateTime.Now) causes an error here
        }).ToListAsync(cancellationToken).ConfigureAwait(false);

var simpleDateSubtraction = await context
    .Where(st => st.TeamManagerId == tmId && st.StartDate >= dateFrom && (st.EndDate ?? DateTime.Now) <= dateTo)
    .GroupBy(st => new { st.UserId, st.StatusId })
    .Select(g => new
    {
        g.Key.UserId,
        g.Key.StatusId,
        Time = g.Sum(st => st.EndDate.Value.Subtract(st.StartDate).Minutes)// null check not done on end date - (st.EndDate ?? DateTime.Now) causes an error here
    }).ToListAsync(cancellationToken).ConfigureAwait(false);

var groupBySimpleSum = await context
    .Where(st => st.TeamManagerId == tmId)
    .GroupBy(st => new { st.TeamManagerId, st.OperationsManagerId })
    .Select(g => new
    {
        g.Key.OperationsManagerId,
        g.Key.TeamManagerId,
        Foo = g.Sum(st => st.UserId) // nonsense but a simple column to sum, this translates fully to SQL
    }).ToListAsync(cancellationToken).ConfigureAwait(false);

Answer 1

首先，EF Core 仍然不支持翻译TimeSpan操作，并且DateTime差异产生TimeSpan，因此EF.Functions.DateDiff方法是正确的方法。

其次，它仍然GroupBy只能在简单的成员访问器表达式上转换聚合。所以你必须Select在GroupBy表达式之前：

var query = context
    .Where(st => st.TeamManagerId == tmId
        && st.StartDate >= dateFrom
        && (st.EndDate ?? DateTime.Now) <= dateTo
    )
    .Select(st => new
    {
        st.UserId,
        st.StatusId,
        Time = EF.Functions.DateDiffMinute(st.StartDate, st.EndDate ?? DateTime.Now)
    })
    .GroupBy(st => new { st.UserId, st.StatusId })
    .Select(g => new
    {
        g.Key.UserId,
        g.Key.StatusId,
        Time = g.Sum(st => st.Time)
    });

或使用GroupBy允许预先选择聚合源的重载：

var query = context
    .Where(st => st.TeamManagerId == tmId
        && st.StartDate >= dateFrom
        && (st.EndDate ?? DateTime.Now) <= dateTo
    )
    .GroupBy(st => new { st.UserId, st.StatusId }, st => new
    {
        Time = EF.Functions.DateDiffMinute(st.StartDate, st.EndDate ?? DateTime.Now)
    })
    .Select(g => new
    {
        g.Key.UserId,
        g.Key.StatusId,
        Time = g.Sum(st => st.Time)
    });