Ensures not to add new indexes if they already exist

src/Umbraco.Core/Persistence/DatabaseModelDefinitions/DbIndexDefinition.cs

@@ -0,0 +1,13 @@
+namespace Umbraco.Core.Persistence.DatabaseModelDefinitions
+{
+    /// <summary>
+    /// Represents a database index definition retreived by querying the database
+    /// </summary>
+    internal class DbIndexDefinition
+    {
+        public virtual string IndexName { get; set; }
+        public virtual string TableName { get; set; }
+        public virtual string ColumnName { get; set; }
+        public virtual bool IsUnique { get; set; }
+    }
+}