Dear developers,

We have recently experienced an issue moving to the latest release. In one of our use cases we are setting a large number of custom properties to an Excel (XLSX) file and it seems that in recent versions something was changed and this process became much slower. Consider the following code:


public class PoiTest {
    public static void main(String[] args) throws IOException {
        try (FileInputStream fis = new FileInputStream("test.xlsx")) {
            XSSFWorkbook workbook = new XSSFWorkbook(fis);

            POIXMLProperties.CustomProperties properties = workbook.getProperties().getCustomProperties();

            IntStream.range(0, 10000).forEach(i -> {
                long ts = System.currentTimeMillis();
                properties.addProperty("property" + i, "value" + 1);
                System.out.println(i + " time taken " + (System.currentTimeMillis() - ts));
            });
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

You will see that time is constantly increasing. The investigation led me to conclude that the cause is the call to 'nextPid()' method in 'CustomProperties' class (defined in 'POIXMLProperties'). If you notice, every time the method is called, it iterates over the whole structure to find out which is the latest pid. In our case, since we do the changes sequentially, we have implemented a workaround in our code base to cache pid, in more general case I am not sure what should be a solution (if any), but performance after some point deteriorates so much that it makes application unusable.

Best regards,
Serhiy.