A custom database event intended for pre-Umbraco v7.2 website using ArcheType which generates long data type prevalues.

CustomDatabaseEvents.cs

using System;
using My.Website.ExtensionMethods;
using Umbraco.Core;
using Umbraco.Core.Persistence;

namespace My.Website.Events {
    public class CustomDatabaseEvents : ApplicationEventHandler {
        protected override void ApplicationStarted(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext) {
            ApplyUmbracoDatabaseHotfixForLongArchetypeModels(applicationContext.DatabaseContext.Database);
        }

        private void ApplyUmbracoDatabaseHotfixForLongArchetypeModels(UmbracoDatabase db) {
            const string tableName = "cmsDataTypePreValues";
            const string columnName = "value";
            const string expectedColumnDataType = "ntext";

            if (db.TableExist(tableName)) {
                var columnDataType = db.GetColumnDataType(tableName, columnName);
                var hasValidField = string.Equals(columnDataType, expectedColumnDataType,
                    StringComparison.OrdinalIgnoreCase);

                if (hasValidField == false) {
                    var updateSql = string.Format("ALTER TABLE {0} ALTER COLUMN {1} {2}", tableName, columnName,
                        expectedColumnDataType);

                    db.Execute(updateSql);
                }
            }
        }
    }
}

ExtensionMethods.cs

using Umbraco.Core.Persistence;

namespace My.Website.ExtensionMethods {
    public static class CustomDatabaseExtensionMethods {
        public static string GetColumnDataType(this Database db, string tableName, string columName) {
            var query =
                new Sql().Select("DATA_TYPE").From("INFORMATION_SCHEMA.COLUMNS")
                    .Where(string.Format("(TABLE_NAME = '{0}') AND (COLUMN_NAME = '{1}')", tableName, columName));

            return db.ExecuteScalar<string>(query);
        }
    }
}