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Replacement for EF Core .Contains, that avoids SQL Server plan cache pollution
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using System.Linq.Expressions; | |
namespace Microsoft.EntityFrameworkCore | |
{ | |
public static class IQueryableExtensions | |
{ | |
public static IQueryable<TQuery> In<TKey, TQuery>( | |
this IQueryable<TQuery> queryable, | |
IEnumerable<TKey> values, | |
Expression<Func<TQuery, TKey>> keySelector) | |
{ | |
ArgumentNullException.ThrowIfNull(values); | |
ArgumentNullException.ThrowIfNull(keySelector); | |
if (!values.Any()) | |
{ | |
return queryable.Take(0); | |
} | |
var distinctValues = Bucketize(values); | |
if (distinctValues.Length > 2048) | |
{ | |
throw new ArgumentException("Too many parameters for SQL Server, reduce the number of parameters", nameof(keySelector)); | |
} | |
var expr = CreateBalancedORExpression(distinctValues, keySelector.Body, 0, distinctValues.Length - 1); | |
var clause = Expression.Lambda<Func<TQuery, bool>>(expr, keySelector.Parameters); | |
return queryable.Where(clause); | |
} | |
private static BinaryExpression CreateBalancedORExpression<TKey>(TKey[] values, Expression keySelectorBody, int start, int end) | |
{ | |
if (start == end) | |
{ | |
var v1 = values[start]; | |
return Expression.Equal(keySelectorBody, ((Expression<Func<TKey>>)(() => v1)).Body); | |
} | |
else if (start + 1 == end) | |
{ | |
var v1 = values[start]; | |
var v2 = values[end]; | |
return Expression.OrElse( | |
Expression.Equal(keySelectorBody, ((Expression<Func<TKey>>)(() => v1)).Body), | |
Expression.Equal(keySelectorBody, ((Expression<Func<TKey>>)(() => v2)).Body)); | |
} | |
else | |
{ | |
int mid = (start + end) / 2; | |
return Expression.OrElse( | |
CreateBalancedORExpression(values, keySelectorBody, start, mid), | |
CreateBalancedORExpression(values, keySelectorBody, mid + 1, end)); | |
} | |
} | |
private static TKey[] Bucketize<TKey>(IEnumerable<TKey> values) | |
{ | |
var distinctValues = new HashSet<TKey>(values).ToArray(); | |
var originalLength = distinctValues.Length; | |
int bucket = (int)Math.Pow(2, Math.Ceiling(Math.Log(originalLength, 2))); | |
if (originalLength == bucket) return distinctValues; | |
var lastValue = distinctValues[originalLength - 1]; | |
Array.Resize(ref distinctValues, bucket); | |
distinctValues.AsSpan().Slice(originalLength).Fill(lastValue); | |
return distinctValues; | |
} | |
} | |
} |
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@clement911 Feel free to do with this snippet whatever you want. It is just a sample.