DataAdapter.Update () performance

I have a relatively simple procedure that looks at the database records for media files, calculates the width, height, and size of the file, and writes them back to the database.

SQLite database, using System.Data.SQLite library, processes ~ 4000 rows. I load all rows into an ADO table, update the rows / columns with the new values, and then run the adapter .Update (table); On him.

Loading dataset from db tables for half a second or so, updating all rows with image width / height and getting file length from FileInfo took maybe 30 seconds. Good.

.Update adapter (table); the team took somewhere around 5-7 minutes to run.

It seems terribly over the top. The id is PK INTEGER, and hence - according to the SQLite docs, is indexed per se, but I can't help but think that if I ran a separate update command for each individual update, it would be much faster.

I considered ADO / adapters to be relatively low (as opposed to ORM) and this awful performance surprised me. Can anyone shed some light on why it would take 5-7 minutes to update a batch of ~ 4000 records across a local SQLite database?

As possible aside, is there a way to "peek" into how ADO handles this? Internal libraries step by step or ... ??

thank

public static int FillMediaSizes() {
        // returns the count of records updated

        int recordsAffected = 0;

        DataTable table = new DataTable();
        SQLiteDataAdapter adapter = new SQLiteDataAdapter();

        using (SQLiteConnection conn = new SQLiteConnection(Globals.Config.dbAppNameConnectionString))
        using (SQLiteCommand cmdSelect = new SQLiteCommand())
        using (SQLiteCommand cmdUpdate = new SQLiteCommand()) {

            cmdSelect.Connection = conn;
            cmdSelect.CommandText =
                "SELECT ID, MediaPathCurrent, MediaWidth, MediaHeight, MediaFilesizeBytes " +
                "FROM Media " +
                "WHERE MediaType = 1 AND (MediaWidth IS NULL OR MediaHeight IS NULL OR MediaFilesizeBytes IS NULL);";

            cmdUpdate.Connection = conn;
            cmdUpdate.CommandText =
                "UPDATE Media SET MediaWidth = @w, MediaHeight = @h, MediaFilesizeBytes = @b WHERE ID = @id;";

            cmdUpdate.Parameters.Add("@w", DbType.Int32, 4, "MediaWidth");
            cmdUpdate.Parameters.Add("@h", DbType.Int32, 4, "MediaHeight");
            cmdUpdate.Parameters.Add("@b", DbType.Int32, 4, "MediaFilesizeBytes");
            SQLiteParameter param = cmdUpdate.Parameters.Add("@id", DbType.Int32);
            param.SourceColumn = "ID";
            param.SourceVersion = DataRowVersion.Original;

            adapter.SelectCommand = cmdSelect;
            adapter.UpdateCommand = cmdUpdate;

            try {
                conn.Open();
                adapter.Fill(table);
                conn.Close();
            }
            catch (Exception e) {
                Core.ExceptionHandler.HandleException(e, true);
                throw new DatabaseOperationException("", e);
            }

            foreach (DataRow row in table.Rows) {

                try {

                    using (System.Drawing.Image img = System.Drawing.Image.FromFile(row["MediaPathCurrent"].ToString())) {

                        System.IO.FileInfo fi;

                        fi = new System.IO.FileInfo(row["MediaPathCurrent"].ToString());

                        if (img != null) {

                            int width = img.Width;
                            int height = img.Height;
                            long length = fi.Length;

                            row["MediaWidth"] = width;
                            row["MediaHeight"] = height;
                            row["MediaFilesizeBytes"] = (int)length;
                        }
                    }
                }
                catch (Exception e) {
                    Core.ExceptionHandler.HandleException(e);
                    DevUtil.Print(e);
                    continue;
                }
            }                


            try {
                recordsAffected = adapter.Update(table);
            }
            catch (Exception e) {
                Core.ExceptionHandler.HandleException(e);
                throw new DatabaseOperationException("", e);
            }


        }

        return recordsAffected;
    }