Open file with lots of data is pretty slow

[allenz8512]

Such as a sheet with 500000 cells, it cost beyond 1 minute to load, while it cost 4 seconds using NPOI on the same machine.

[rabanti-github]

Hello,
Thank you for your report.
But could you please provide some further information?:

• What version of NanoXLSX do you use (still stable 2.6.7 or already a release candidate of v3)?
• What kind of data are you loading (just strings, numeric data, very volatile data , dates, etc.)?
• Do the cells use a lot of styles?
• How do you load the data (by file, by stream, by file async, by stream async)?
• What is your setup roughly (used .net Version)?

Thank you in advance for clarification.

[allenz8512]

• Version: 2.x or 3.0rc2
• Unity 6.0.17, mono backend，.net standard 2.1
• Use =SEQUENCE(10000,50,0,1) to create 500000 cells in a sheet
• Create some test like below:

        [UnityTest]
        public IEnumerator NanoXLSXRead() => UniTask.ToCoroutine(async () =>
            {
                byte[] bytes = await ExternalAssetUtils.ReadBytes("Test/test_excel");
                DateTime start = DateTime.Now;
                using (MemoryStream stream = new MemoryStream(bytes))
                {
                    Workbook workbook = await WorkbookReader.LoadAsync(stream);
                    Worksheet sheet = workbook.GetWorksheet(0);
                    Cell cell = sheet.GetCell(0, 0);
                    Assert.AreEqual("0", cell.Value.ToString());
                    DateTime end = DateTime.Now;
                    Debug.Log($"NanoXLSX Read: {(end - start).TotalMilliseconds}ms Used");
                }
            }
        );

• Result:

ClosedXML Read: 2838.8302ms Used
NanoXLSX Read: 21846.1548ms Used
NPOI Read: 1466.7362ms Used

[rabanti-github]

Will be part of optimizations (attempts / options) in the upcoming v3 architecture