使用 Entity Framework Core 按类型未知的 JsonDocument 属性分组

Question

我正在使用 Entity Framework Core 3.1.5

我正在尝试按 JsonDocument 的某些属性对实体进行分组，我不知道它的类型。 AdditionalData 是实体的JsonDocument 属性。

我需要在数据库上执行命令。

我设法做到了有两个限制

1. 我指定了属性的类型（使用 GetInt32）
2. 这些命令是在客户端而不是数据库上执行的。

    IEnumerable<MetricEntity> metricEntities = _tenantDbContext.Set<MetricEntity>();
    var ii2 = metricEntities.Where(metric => metric.Name == metricName).GroupBy(e =>
        e.AdditionalData!.RootElement.GetProperty(groupByProperty).GetInt32())
    .Select(entities => new
    {
        Count = entities.Count(), MetType = entities.Key, Ent = entities,
    }).ToList();

我也设法做到了，但没有得到结果中的所有实体 并且限制命令是在客户端而不是数据库上执行的。

var i2 = _tenantDbContext.Set<MetricEntity>()
.Where(metric => metric.Name == metricName)
.GroupBy(e =>
    e.AdditionalData!.RootElement.GetProperty(groupByProperty).GetString())
.Select(entities => new
{
    Count = entities.Count(), MetType = entities.Key
}).ToList();

但是当我将实体添加到结果中时，如下所示：

var i2 = _tenantDbContext.Set<MetricEntity>()
.GroupBy(e =>
    e.AdditionalData!.RootElement.GetProperty(groupByProperty).GetString())
.Select(entities => new
{
    Count = entities.Count(), MetType = entities.Key, ent = entities,
}).ToList();

我收到以下异常：

System.InvalidOperationException: Processing of the LINQ expression '(GroupByShaperExpression:
KeySelector: ((m.AdditionalData)#>>{(@__groupByProperty_1)}),
ElementSelector:(EntityShaperExpression:
    EntityType: MetricEntity
    ValueBufferExpression:
        (ProjectionBindingExpression: EmptyProjectionMember)
    IsNullable: False
)
)' by 'RelationalProjectionBindingExpressionVisitor' failed. This may indicate either a bug or a limitation in EF Core. See https://go.microsoft.com/fwlink/?linkid=2101433 for more detailed information.
   at Microsoft.EntityFrameworkCore.Query.Internal.RelationalProjectionBindingExpressionVisitor.VisitExtension(Expression extensionExpression)
   at System.Linq.Expressions.Expression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Query.Internal.RelationalProjectionBindingExpressionVisitor.Visit(Expression expression)
   at Microsoft.EntityFrameworkCore.Query.Internal.RelationalProjectionBindingExpressionVisitor.VisitNew(NewExpression newExpression)
   at System.Linq.Expressions.NewExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Query.Internal.RelationalProjectionBindingExpressionVisitor.Visit(Expression expression)
   at Microsoft.EntityFrameworkCore.Query.Internal.RelationalProjectionBindingExpressionVisitor.Translate(SelectExpression selectExpression, Expression expression)
   at Microsoft.EntityFrameworkCore.Query.RelationalQueryableMethodTranslatingExpressionVisitor.TranslateSelect(ShapedQueryExpression source, LambdaExpression selector)
   at Microsoft.EntityFrameworkCore.Query.QueryableMethodTranslatingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCallExpression)
   at Microsoft.EntityFrameworkCore.Query.RelationalQueryableMethodTranslatingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCallExpression)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Query.QueryCompilationContext.CreateQueryExecutor[TResult](Expression query)
   at Microsoft.EntityFrameworkCore.Storage.Database.CompileQuery[TResult](Expression query, Boolean async)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.CompileQueryCore[TResult](IDatabase database, Expression query, IModel model, Boolean async)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.<>c__DisplayClass9_0`1.<Execute>b__0()
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQueryCore[TFunc](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQuery[TResult](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.Execute[TResult](Expression query)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryProvider.Execute[TResult](Expression expression)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable`1.GetEnumerator()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)

Answer 1

每个group by 查询应包含一个或多个键 和其他仅在选择语句中具有聚合功能的属性（Sum、Count 等）。 EF 尝试将 LINQ 转换为 SQL 查询并由于没有内部检查而引发异常。

有一个解决方法：

在GroupBy 之前评估表数据。以下代码加载所有MetricEntities 并将其分组到c# 代码中：

var i2 = _tenantDbContext.MetricEntities
.AsEnumerable()
.GroupBy(e =>
    e.AdditionalData!.RootElement.GetProperty(groupByProperty).GetString())
.Select(entities => new
{
    Count = entities.Count(), MetType = entities.Key, ent = entities,
}).ToList();