diff --git a/LiteDB/Database/Collections/Aggregate.cs b/LiteDB/Database/Collections/Aggregate.cs
index 26c4db9ac..03632e859 100644
--- a/LiteDB/Database/Collections/Aggregate.cs
+++ b/LiteDB/Database/Collections/Aggregate.cs
@@ -74,41 +74,22 @@ public bool Exists(Query query)
         /// <summary>
         /// Returns the first/min value from a index field
         /// </summary>
-        public BsonValue Min(string field)
-        {
-            if (string.IsNullOrEmpty(field)) throw new ArgumentNullException(nameof(field));
-
-            return _engine.Value.Min(_name, field);
-        }
-
-        /// <summary>
-        /// Returns the first/min _id field
-        /// </summary>
         public BsonValue Min()
         {
-            return this.Min("_id");
+            return _engine.Value.Min(_name);
         }
 
 
-
         /// <summary>
         /// Returns the last/max value from a index field
         /// </summary>
-        public BsonValue Max(string field)
-        {
-            if (string.IsNullOrEmpty(field)) throw new ArgumentNullException(nameof(field));
-
-            return _engine.Value.Max(_name, field);
-        }
-
-        /// <summary>
-        /// Returns the last/max _id field
-        /// </summary>
         public BsonValue Max()
         {
-            return this.Max("_id");
+            return _engine.Value.Max(_name);
         }
 
+
+
         #endregion
     }
 }
\ No newline at end of file
diff --git a/LiteDB/Engine/Engine/Aggregate.cs b/LiteDB/Engine/Engine/Aggregate.cs
index d78e1248a..82fd511a4 100644
--- a/LiteDB/Engine/Engine/Aggregate.cs
+++ b/LiteDB/Engine/Engine/Aggregate.cs
@@ -8,10 +8,9 @@ public partial class LiteEngine
         /// <summary>
         /// Returns first value from an index (first is min value)
         /// </summary>
-        public BsonValue Min(string collection, string field)
+        public BsonValue Min(string collection)
         {
             if (collection.IsNullOrWhiteSpace()) throw new ArgumentNullException(nameof(collection));
-            if (field.IsNullOrWhiteSpace()) throw new ArgumentNullException(nameof(field));
 
 
             var col = this.GetCollectionPage(collection, false);
@@ -19,7 +18,7 @@ public BsonValue Min(string collection, string field)
             if (col == null) return BsonValue.MinValue;
 
             // get index (no index, no min)
-            var index = col.GetIndex(field);
+            var index = col.PK;
 
             if (index == null) return BsonValue.MinValue;
 
@@ -35,18 +34,16 @@ public BsonValue Min(string collection, string field)
         /// <summary>
         /// Returns last value from an index (last is max value)
         /// </summary>
-        public BsonValue Max(string collection, string field)
+        public BsonValue Max(string collection)
         {
             if (collection.IsNullOrWhiteSpace()) throw new ArgumentNullException(nameof(collection));
-            if (field.IsNullOrWhiteSpace()) throw new ArgumentNullException(nameof(field));
-
 
             var col = this.GetCollectionPage(collection, false);
 
             if (col == null) return BsonValue.MaxValue;
 
             // get index (no index, no max)
-            var index = col.GetIndex(field);
+            var index = col.PK;
 
             if (index == null) return BsonValue.MaxValue;
 
diff --git a/LiteDB/Engine/Engine/Insert.cs b/LiteDB/Engine/Engine/Insert.cs
index 423291677..eb58dab2f 100644
--- a/LiteDB/Engine/Engine/Insert.cs
+++ b/LiteDB/Engine/Engine/Insert.cs
@@ -72,7 +72,7 @@ private void InsertDocument(CollectionPage col, BsonDocument doc, BsonType autoI
             // ** this code can be removed when datafile change from 7 (HeaderPage.FILE_VERSION) **
             if (col.Sequence == 0 && col.DocumentCount > 0)
             {
-                var max = this.Max(col.CollectionName, "_id");
+                var max = this.Max(col.CollectionName);
 
                 // if max value is a number, convert to Sequence last value
                 // if not, just set sequence as document count
diff --git a/LiteDB/Engine/Pages/CollectionPage.cs b/LiteDB/Engine/Pages/CollectionPage.cs
index aefdd7007..f1e408b06 100644
--- a/LiteDB/Engine/Pages/CollectionPage.cs
+++ b/LiteDB/Engine/Pages/CollectionPage.cs
@@ -151,21 +151,11 @@ protected override void WriteContent(ByteWriter writer)
         /// </summary>
         public CollectionIndex GetFreeIndex()
         {
-            for (byte i = 0; i < this.Indexes.Length; i++)
-            {
-                if (this.Indexes[i].IsEmpty) return this.Indexes[i];
-            }
+            if (this.Indexes[0].IsEmpty) return this.Indexes[0];
 
             throw LiteException.IndexLimitExceeded(this.CollectionName);
         }
 
-        /// <summary>
-        /// Get index from field name (index field name is case sensitive) - returns null if not found
-        /// </summary>
-        public CollectionIndex GetIndex(string field)
-        {
-            return this.Indexes.FirstOrDefault(x => x.Field == field);
-        }
 
         /// <summary>
         /// Get primary key index (_id index)