GetValues copies only what the array holds

DuckDB.NET.Data/DuckDBDataReader.cs

@@ -305,17 +305,22 @@ public override object GetProviderSpecificValue(int ordinal)
 
     public override int GetValues(object[] values)
     {
+        ArgumentNullException.ThrowIfNull(values);
         CheckRowRead();
 
         var offset = rowsReadFromCurrentChunk - 1;
 
-        for (var i = 0; i < FieldCount; i++)
+        // IDataRecord.GetValues: "You can pass an Object array that contains fewer than the number of columns that are
+        // contained in the resulting row. Only the amount of data the Object array holds is copied to the array."
+        var count = Math.Min(values.Length, FieldCount);
+
+        for (var i = 0; i < count; i++)
         {
             var reader = vectorReaders[i];
             values[i] = reader.IsValid(offset) ? reader.GetValue(offset) : DBNull.Value;
         }
 
-        return FieldCount;
+        return count;
     }
 
     public override Stream GetStream(int ordinal)

DuckDB.NET.Test/DuckDBDataReaderTests.cs

@@ -843,5 +843,28 @@ public void GetOrdinalThrowsIndexOutOfRangeForAnUnknownName()
 
         reader.Invoking(r => r.GetOrdinal("missing")).Should().Throw<IndexOutOfRangeException>();
     }
-}
 
+    // https://learn.microsoft.com/dotnet/api/system.data.idatarecord.getvalues: "You can pass an Object array that
+    // contains fewer than the number of columns that are contained in the resulting row. Only the amount of data the
+    // Object array holds is copied to the array. You can also pass an Object array whose length is more than the
+    // number of columns that are contained in the resulting row."
+    [Fact]
+    public void GetValuesCopiesOnlyWhatTheArrayHolds()
+    {
+        Command.CommandText = "SELECT 1 AS a, 2 AS b, 3 AS c";
+        using var reader = Command.ExecuteReader();
+        reader.Read().Should().BeTrue();
+
+        reader.GetValues(new object[0]).Should().Be(0);
+        reader.Invoking(r => r.GetValues(null!)).Should().Throw<ArgumentNullException>();
+
+        var shorter = new object[2];
+        reader.GetValues(shorter).Should().Be(2);
+        shorter.Should().Equal(1, 2);
+
+        var longer = new object[5];
+        reader.GetValues(longer).Should().Be(3);
+        longer.Take(3).Should().Equal(1, 2, 3);
+        longer.Skip(3).Should().AllSatisfy(value => value.Should().BeNull());
+    }
+}