如何在SQL中執行此EF Core嵌套日期比較查詢

Question

使用.Net Core 2.1和EF Core 2.1.1和SQL Server

我正在嘗試提取Organizations及其Communications清單
然后，我想將其限制為最近6個月內未進行任何Communications的用戶

這是我略過的ViewModels：

public class OrganizationViewModel
{
    public Guid Id { get; set; }
    public IEnumerable<CommunicationViewModel> CommunicationViewModels { get; set;
}

public class CommunicationViewModel
{
    public Guid Id { get; set; }
    public DateTime Date { get; set; }

    public Guid OrganizationViewModelId { get; set; }
    public OrganizationViewModel OrganizationViewModel { get; set; }
}

這是我的查詢：

DateTime sixMonthsAgo = DateTime.Today.AddMonths(-6);
int pageIndex = 1; // Would be passed in
int pageSize = 3;

IQueryable<OrganizationViewModel> query = _context.Organizations
    .AsNoTracking()
    .Select(organization => new OrganizationViewModel
    {
        CommunicationViewModels = organization.Communications.Select(communication => new CommunicationViewModel
        {
            Date = communication.Date
        })              
        .OrderByDescending(communication => communication.Date)
        .Take(1)
        .ToList()
    })
    .Where(organization => 
        (!searchViewModel.LimitToLastSixMonths || 
            organization.CommunicationViewModels.Any(communication => communication.Date <= sixMonthsAgo)));

int totalAmount = await query.CountAsync();
List<OrganizationViewModel> items = await query
            .Skip((pageIndex - 1) * pageSize)
            .Take(pageSize)
            .ToListAsync();

這樣可以得到預期的結果，但是當我點擊.CountAsync()和時，可以在日志中看到對每條記錄執行此查詢。 Skip(..).Take(..) ：

SELECT CASE
    WHEN EXISTS (
        SELECT 1
        FROM (
            SELECT TOP(1) [comm].[Date]
            FROM [Communications] AS [comm]
            WHERE @_outer_Id = [comm].[OrganizationId]
            ORDER BY [comm].[Date] DESC
        ) AS [t]
        WHERE [t].[Date] <= @__sixMonthsAgo_0)
    THEN CAST(1 AS BIT) ELSE CAST(0 AS BIT)
END

當.CountAsync() （稍作編輯）時，我也看到這些警告：

Microsoft.EntityFrameworkCore.Query：警告：LINQ表達式
'where (False OrElse {from CommunicationViewModel cvm in {from Communication comm in value(..EntityQueryable'1[..Models.Communication]) orderby [comm].Date desc where ?= (Property([o], "Id") == Property([comm], "OrganizationId")) =? select new CommunicationViewModel() {Date = [comm].Date} => Take(1) => AsQueryable()} where ([cvm].Date <= __sixMonthsAgo_0) select [cvm] => Any()})'無法翻譯，將在本地進行評估。
Microsoft.EntityFrameworkCore.Query：警告：LINQ表達式'Count（）'無法翻譯，將在本地進行評估。

以及調用.Take(..).Skip(..)時的類似錯誤：

Microsoft.EntityFrameworkCore.Query：警告：LINQ表達式
same as above無法翻譯，將在本地進行評估。 Microsoft.EntityFrameworkCore.Query：警告：LINQ表達式'Skip（__ p_1）'無法翻譯，將在本地進行評估。
Microsoft.EntityFrameworkCore.Query：警告：LINQ表達式“ Take（__ p_2）”無法翻譯，將在本地進行評估。

當searchViewModel.LimitToLastSixMonths為false時，不會發生這種情況

關於如何重寫查詢以不對每個記錄在本地執行該查詢的任何建議？

Answer 1

如果您嘗試將Navigation屬性包含在select中，該怎么辦：

IQueryable<OrganizationViewModel> query = _context.Organizations
    .Include(o => o.CommunicationViewModels)
...

Answer 2

我想到了！

這是我的新查詢：

DateTime sixMonthsAgo = DateTime.Today.AddMonths(-6);
int pageIndex = 1; // Would be passed in
int pageSize = 3;

IQueryable<OrganizationViewModel> query = _context.Organizations
    .AsNoTracking()
    .Select(organization => new OrganizationViewModel
    {
        CommunicationViewModels = organization.Communications.Select(communication  => 
            new CommunicationViewModel
            {
                Id = communication.Id,
                Date = communication.Date
            })
            .OrderByDescending(communicationViewModel => communicationViewModel.Date)
            .Take(1)
            .Where(communicationViewModel => communicationViewModel.Date <= sixMonthsAgo)
            .AsQueryable()
    })
    .Where(organizationViewModel =>
        (!searchViewModel.LimitToLastSixMonths || organizationViewModel.CommunicationViewModels.Any()));

int totalAmount = await query.CountAsync();
List<OrganizationViewModel> items = await query
            .Skip((pageIndex - 1) * pageSize)
            .Take(pageSize)
            .ToListAsync();

現在，當searchViewModel.LimitToLastSizeMonths為true時， searchViewModel.LimitToLastSizeMonths生成這兩個查詢：

SELECT COUNT(*)
FROM [Organizations] AS [organization]
WHERE EXISTS (
    SELECT 1
    FROM (
        SELECT [t].[Id], [t].[Date]
        FROM (
            SELECT TOP(1) [communication].[Id], [communication].[Date]
            FROM [Communications] AS [communication]
            WHERE [organization].[Id] = [communication].[OrganizationId]
            ORDER BY [communication].[Date] DESC
        ) AS [t]
        WHERE [t].[Date] <= @__sixMonthsAgo_0
    ) AS [t0])


SELECT [organization].[Id]
FROM [Organizations] AS [organization]
WHERE EXISTS (
    SELECT 1
    FROM (
        SELECT [t].[Id], [t].[Date]
        FROM (
            SELECT TOP(1) [communication].[Id], [communication].[Date]
            FROM [Communications] AS [communication]
            WHERE [organization].[Id] = [communication].[OrganizationId]
            ORDER BY [communication].[Date] DESC
        ) AS [t]
        WHERE [t].[Date] <= @__sixMonthsAgo_0
    ) AS [t0])
ORDER BY (SELECT 1)
OFFSET @__p_1 ROWS FETCH NEXT @__p_2 ROWS ONLY

如果沒有.AsQueryable()它將返回檢查每個記錄並在本地執行計數和滑雪/ .AsQueryable() 。