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Fixed inefficient cache usage. #694

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Merged
merged 2 commits into from
Feb 21, 2020
Merged

Fixed inefficient cache usage. #694

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7784f9d
Fixed inefficient cache usage.
Feb 19, 2020
70b34f6
Empty commit to restart timed-out Travis build
Feb 19, 2020
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31 changes: 28 additions & 3 deletions src/JsonApiDotNetCore/Extensions/IQueryableExtensions.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -247,7 +247,7 @@ private static IQueryable<TSource> CallGenericWhereMethod<TSource>(IQueryable<TS
PropertyInfo relationProperty = null;
PropertyInfo property = null;
MemberExpression left;
ConstantExpression right;
Expression right;

// {model}
var parameter = Expression.Parameter(concreteType, "model");
Expand Down Expand Up @@ -287,8 +287,8 @@ private static IQueryable<TSource> CallGenericWhereMethod<TSource>(IQueryable<TS
// convert the incoming value to the target value type
// "1" -> 1
var convertedValue = TypeHelper.ConvertType(filter.Value, property.PropertyType);
// {1}
right = Expression.Constant(convertedValue, property.PropertyType);

right = CreateTupleAccessForConstantExpression(convertedValue, property.PropertyType);
}

var body = GetFilterExpressionLambda(left, right, filter.Operation);
Expand All @@ -302,6 +302,31 @@ private static IQueryable<TSource> CallGenericWhereMethod<TSource>(IQueryable<TS
}
}

private static Expression CreateTupleAccessForConstantExpression(object value, Type type)
{
// To enable efficient query plan caching, inline constants (that vary per request) should be converted into query parameters.
// https://stackoverflow.com/questions/54075758/building-a-parameterized-entityframework-core-expression

// This method can be used to change a query like:
// SELECT ... FROM ... WHERE x."Age" = 3
// into:
// SELECT ... FROM ... WHERE x."Age" = @p0

// The code below builds the next expression for a type T that is unknown at compile time:
// Expression.Property(Expression.Constant(Tuple.Create<T>(value)), "Item1")
// Which represents the next C# code:
// Tuple.Create<T>(value).Item1;

MethodInfo tupleCreateMethod = typeof(Tuple).GetMethods()
.Single(m => m.Name == "Create" && m.IsGenericMethod && m.GetGenericArguments().Length == 1);
MethodInfo constructedTupleCreateMethod = tupleCreateMethod.MakeGenericMethod(type);

ConstantExpression constantExpression = Expression.Constant(value, type);

MethodCallExpression tupleCreateCall = Expression.Call(constructedTupleCreateMethod, constantExpression);
return Expression.Property(tupleCreateCall, "Item1");
}

private static IQueryable<TSource> CallGenericSelectMethod<TSource>(IQueryable<TSource> source, List<string> columns)
{
var sourceBindings = new List<MemberAssignment>();
Expand Down