Add StructureSettings and have EliasFano read it with default value fallback

Author: Genbox

Src/FastData/Config/DataConfig.cs

@@ -1,4 +1,4 @@
-namespace Genbox.FastData.Config;
+namespace Genbox.FastData.Config;
 
 public abstract class DataConfig
 {
@@ -31,4 +31,7 @@ public abstract class DataConfig
     /// performance.
     /// </summary>
     public int HashCapacityFactor { get; set; } = 1;
+
+    /// <summary>Can be used to give advanced fine-tuning parameters to individual data structures</summary>
+    public Dictionary<string, object> StructureSettings { get; } = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
 }

Src/FastData/FastDataGenerator.cs

@@ -283,7 +283,7 @@ private static string GenerateNumericInternal<TKey, TValue>(ReadOnlyMemory<TKey>
 
         LogStructureType(logger, structureType.Name);
 
-        IStructure<TKey, TValue, IContext> structure = NumericStructureFactory<TKey, TValue>(structureType, props, cacheHashData!, sorted);
+        IStructure<TKey, TValue, IContext> structure = NumericStructureFactory<TKey, TValue>(cfg, structureType, props, cacheHashData!, sorted);
 
         IEarlyExit[] earlyExits = CombineEarlyExits(structure.GetMandatoryExits(), NumericEarlyExits<TKey>.GetCandidates(type, props.MinKeyValue, props.MaxKeyValue, props.Range, props.BitMask, (uint)keys.Length, cfg.EarlyExitConfig));
 
@@ -321,7 +321,7 @@ private static IEarlyExit[] CombineEarlyExits(IEnumerable<IEarlyExit> mandatoryE
         return combined.ToArray();
     }
 
-    private static IStructure<TKey, TValue, IContext> NumericStructureFactory<TKey, TValue>(Type type, NumericKeyProperties<TKey> props, HashData hashData, bool sorted)
+    private static IStructure<TKey, TValue, IContext> NumericStructureFactory<TKey, TValue>(DataConfig cfg, Type type, NumericKeyProperties<TKey> props, HashData hashData, bool sorted)
     {
         if (type == typeof(ArrayStructure<,>))
             return new ArrayStructure<TKey, TValue>();
@@ -336,7 +336,7 @@ private static IStructure<TKey, TValue, IContext> NumericStructureFactory<TKey,
         if (type == typeof(ConditionalStructure<,>))
             return new ConditionalStructure<TKey, TValue>();
         if (type == typeof(EliasFanoStructure<,>))
-            return new EliasFanoStructure<TKey, TValue>(props.MinKeyValue, props.MaxKeyValue, props.ValueConverter, sorted, 128); // TODO: Make skip a config
+            return new EliasFanoStructure<TKey, TValue>(props.MinKeyValue, props.MaxKeyValue, props.ValueConverter, sorted, GetSetting(cfg, "SkipQuantum", 128));
         if (type == typeof(HashTableStructure<,>))
             return new HashTableStructure<TKey, TValue>(hashData);
         if (type == typeof(HashTableCompactStructure<,>))
@@ -353,6 +353,14 @@ private static IStructure<TKey, TValue, IContext> NumericStructureFactory<TKey,
         throw new InvalidOperationException($"Unsupported DataStructure {type}");
     }
 
+    private static T GetSetting<T>(DataConfig cfg, string key, T defaultValue)
+    {
+        if (!cfg.StructureSettings.TryGetValue(key, out object? value))
+            return defaultValue;
+
+        return (T)value;
+    }
+
     private sealed class UsedFunctionVisitor : ExpressionVisitor
     {
         internal StringFunction Functions { get; private set; }