Google-sheets – Filtering a protected column

I am fighting with the same problem, I think it is because the protected cells are set statically and not affected by the sort. The reason is that Google Spreadsheets do not allow the selection of multiple ranges with are not adjacent to each other.

In other words, If you have a defined protected range in the Spreadsheet, it will always be the same rows and columns, regardless of your actions (adding rows and columns, sorting them and so on).

This is a huge drawback of the Google Spreadsheets.

The key approach is to minimize the API calls. Performing those in for loops will slow down the process considerably, especially with 900 rows. I've re-worked your code in such a way, that it calls for the Spreadsheet API only twice:

function open_interventions() {
  var sheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();

  // start logger time  
  var start = new Date();

  // collect data and sort
  var data = sheet.getRange(2, 1, sheet.getLastRow()-1, sheet.getLastColumn())
    .sort([
      {column: 1, ascending: true}, 
      {column: 3, ascending: false},
      {column: 2, ascending: true}])
    .getValues();

  // set counters
  var cFirst = 0, cSecond = 0;

  // itterate to find number of "Open" rows
  for(var i=0, dLen=data.length; i<dLen; i++) {
    if(data[i][0] == 'Open') {
      cFirst++;
    } 
  }

  // itterate through array (backwards) to calculate the rowIndex 
  for(var j=dLen=data.length-1; j>=0; j--) {
    if(data[j][0] != 'Open') {      
      cSecond++;
    } else {
      break;
    }
  }

  // calculate rowIndex
  var rIndex = data.length - (cFirst+cSecond);

  // hide all rows
  sheet.hideRows(2, data.length); 

  // show (unhide) only "Open" rows
  sheet.showRows(rIndex+2, cFirst); 

  sheet.setActiveSelection("D1")
    .setValue("Execution time (ms): " + (new Date() - start).toString());
}

I've added a time tracker thingy to it, so that you can monitor the execution speed. See example file I created: Efficient Sorting. When the file is opened, it will add another menu item called Sorting. There you can play around and see what happens.