Faster way to find the first empty row in a Google Sheet column
Seeing this old post with 5k views I first checked the 'best answer' and was quite surprised by its content... this was a very slow process indeed ! then I felt better when I saw Don Kirkby's answer, the array approach is indeed much more efficient !
But how much more efficient ?
So I wrote this little test code on a spreadsheet with 1000 rows and here are the results : (not bad !... no need to tell which one is which...)
and here is the code I used :
function onOpen() {
var menuEntries = [ {name: "test method 1", functionName: "getFirstEmptyRow"},
{name: "test method 2 (array)", functionName: "getFirstEmptyRowUsingArray"}
];
var sh = SpreadsheetApp.getActiveSpreadsheet();
sh.addMenu("run tests",menuEntries);
}
function getFirstEmptyRow() {
var time = new Date().getTime();
var spr = SpreadsheetApp.getActiveSpreadsheet();
var ran = spr.getRange('A:A');
for (var i= ran.getLastRow(); i>0; i--){
if(ran.getCell(i,1).getValue()){
break;
}
}
Browser.msgBox('lastRow = '+Number(i+1)+' duration = '+Number(new Date().getTime()-time)+' mS');
}
function getFirstEmptyRowUsingArray() {
var time = new Date().getTime();
var sh = SpreadsheetApp.getActiveSpreadsheet();
var ss = sh.getActiveSheet();
var data = ss.getDataRange().getValues();
for(var n =data.length ; n<0 ; n--){
if(data[n][0]!=''){n++;break}
}
Browser.msgBox('lastRow = '+n+' duration = '+Number(new Date().getTime()-time)+' mS');
}
function fillSheet(){
var sh = SpreadsheetApp.getActiveSpreadsheet();
var ss = sh.getActiveSheet();
for(var r=1;r<1000;++r){
ss.appendRow(['filling values',r,'not important']);
}
}
And the test spreadsheet to try it yourself :-)
EDIT :
Following Mogsdad's comment, I should mention that these function names are indeed a bad choice... It should have been something like getLastNonEmptyCellInColumnAWithPlentyOfSpaceBelow() which is not very elegant (is it ?) but more accurate and coherent with what it actually returns.
Comment :
Anyway, my point was to show the speed of execution of both approaches, and it obviously did it (didn't it ? ;-)
This question has now had more than 12K views - so it's time for an update, as the performance characteristics of New Sheets are different than when Serge ran his initial tests.
Good news: performance is much better across the board!
Fastest:
As in the first test, reading the sheet's data just once, then operating on the array, gave a huge performance benefit. Interestingly, Don's original function performed much better than the modified version that Serge tested. (It appears that while is faster than for, which isn't logical.)
The average execution time on the sample data is just 38ms, down from the previous 168ms.
// Don's array approach - checks first column only
// With added stopping condition & correct result.
// From answer https://stackoverflow.com/a/9102463/1677912
function getFirstEmptyRowByColumnArray() {
var spr = SpreadsheetApp.getActiveSpreadsheet();
var column = spr.getRange('A:A');
var values = column.getValues(); // get all data in one call
var ct = 0;
while ( values[ct] && values[ct][0] != "" ) {
ct++;
}
return (ct+1);
}
Test results:
Here are the results, summarized over 50 iterations in a spreadsheet with 100 rows x 3 columns (filled with Serge's test function).
The function names match the code in the script below.
"First empty row"
The original ask was to find the first empty row. None of the previous scripts actually deliver on that. Many check just one column, which means that they can give false positive results. Others only find the first row that follows all data, meaning that empty rows in non-contiguous data get missed.
Here's a function that does meet the spec. It was included in the tests, and while slower than the lightning-fast single-column checker, it came in at a respectable 68ms, a 50% premium for a correct answer!
/**
* Mogsdad's "whole row" checker.
*/
function getFirstEmptyRowWholeRow() {
var sheet = SpreadsheetApp.getActiveSheet();
var range = sheet.getDataRange();
var values = range.getValues();
var row = 0;
for (var row=0; row<values.length; row++) {
if (!values[row].join("")) break;
}
return (row+1);
}
Complete script:
If you want to repeat the tests, or add your own function to the mix as a comparison, just take the whole script and use it in a spreadsheet.
/**
* Set up a menu option for ease of use.
*/
function onOpen() {
var menuEntries = [ {name: "Fill sheet", functionName: "fillSheet"},
{name: "test getFirstEmptyRow", functionName: "testTime"}
];
var sh = SpreadsheetApp.getActiveSpreadsheet();
sh.addMenu("run tests",menuEntries);
}
/**
* Test an array of functions, timing execution of each over multiple iterations.
* Produce stats from the collected data, and present in a "Results" sheet.
*/
function testTime() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
ss.getSheets()[0].activate();
var iterations = parseInt(Browser.inputBox("Enter # of iterations, min 2:")) || 2;
var functions = ["getFirstEmptyRowByOffset", "getFirstEmptyRowByColumnArray", "getFirstEmptyRowByCell","getFirstEmptyRowUsingArray", "getFirstEmptyRowWholeRow"]
var results = [["Iteration"].concat(functions)];
for (var i=1; i<=iterations; i++) {
var row = [i];
for (var fn=0; fn<functions.length; fn++) {
var starttime = new Date().getTime();
eval(functions[fn]+"()");
var endtime = new Date().getTime();
row.push(endtime-starttime);
}
results.push(row);
}
Browser.msgBox('Test complete - see Results sheet');
var resultSheet = SpreadsheetApp.getActive().getSheetByName("Results");
if (!resultSheet) {
resultSheet = SpreadsheetApp.getActive().insertSheet("Results");
}
else {
resultSheet.activate();
resultSheet.clearContents();
}
resultSheet.getRange(1, 1, results.length, results[0].length).setValues(results);
// Add statistical calculations
var row = results.length+1;
var rangeA1 = "B2:B"+results.length;
resultSheet.getRange(row, 1, 3, 1).setValues([["Avg"],["Stddev"],["Trimmed\nMean"]]);
var formulas = resultSheet.getRange(row, 2, 3, 1);
formulas.setFormulas(
[[ "=AVERAGE("+rangeA1+")" ],
[ "=STDEV("+rangeA1+")" ],
[ "=AVERAGEIFS("+rangeA1+","+rangeA1+',"<"&B$'+row+"+3*B$"+(row+1)+","+rangeA1+',">"&B$'+row+"-3*B$"+(row+1)+")" ]]);
formulas.setNumberFormat("##########.");
for (var col=3; col<=results[0].length;col++) {
formulas.copyTo(resultSheet.getRange(row, col))
}
// Format for readability
for (var col=1;col<=results[0].length;col++) {
resultSheet.autoResizeColumn(col)
}
}
// Omiod's original function. Checks first column only
// Modified to give correct result.
// question https://stackoverflow.com/questions/6882104
function getFirstEmptyRowByOffset() {
var spr = SpreadsheetApp.getActiveSpreadsheet();
var cell = spr.getRange('a1');
var ct = 0;
while ( cell.offset(ct, 0).getValue() != "" ) {
ct++;
}
return (ct+1);
}
// Don's array approach - checks first column only.
// With added stopping condition & correct result.
// From answer https://stackoverflow.com/a/9102463/1677912
function getFirstEmptyRowByColumnArray() {
var spr = SpreadsheetApp.getActiveSpreadsheet();
var column = spr.getRange('A:A');
var values = column.getValues(); // get all data in one call
var ct = 0;
while ( values[ct] && values[ct][0] != "" ) {
ct++;
}
return (ct+1);
}
// Serge's getFirstEmptyRow, adapted from Omiod's, but
// using getCell instead of offset. Checks first column only.
// Modified to give correct result.
// From answer https://stackoverflow.com/a/18319032/1677912
function getFirstEmptyRowByCell() {
var spr = SpreadsheetApp.getActiveSpreadsheet();
var ran = spr.getRange('A:A');
var arr = [];
for (var i=1; i<=ran.getLastRow(); i++){
if(!ran.getCell(i,1).getValue()){
break;
}
}
return i;
}
// Serges's adaptation of Don's array answer. Checks first column only.
// Modified to give correct result.
// From answer https://stackoverflow.com/a/18319032/1677912
function getFirstEmptyRowUsingArray() {
var sh = SpreadsheetApp.getActiveSpreadsheet();
var ss = sh.getActiveSheet();
var data = ss.getDataRange().getValues();
for(var n=0; n<data.length ; n++){
if(data[n][0]==''){n++;break}
}
return n+1;
}
/**
* Mogsdad's "whole row" checker.
*/
function getFirstEmptyRowWholeRow() {
var sheet = SpreadsheetApp.getActiveSheet();
var range = sheet.getDataRange();
var values = range.getValues();
var row = 0;
for (var row=0; row<values.length; row++) {
if (!values[row].join("")) break;
}
return (row+1);
}
function fillSheet(){
var sh = SpreadsheetApp.getActiveSpreadsheet();
var ss = sh.getActiveSheet();
for(var r=1;r<1000;++r){
ss.appendRow(['filling values',r,'not important']);
}
}
// Function to test the value returned by each contender.
// Use fillSheet() first, then blank out random rows and
// compare results in debugger.
function compareResults() {
var a = getFirstEmptyRowByOffset(),
b = getFirstEmptyRowByColumnArray(),
c = getFirstEmptyRowByCell(),
d = getFirstEmptyRowUsingArray(),
e = getFirstEmptyRowWholeRow(),
f = getFirstEmptyRowWholeRow2();
debugger;
}
The Google Apps Script blog had a post on optimizing spreadsheet operations that talked about batching reads and writes that could really speed things up. I tried your code on a spreadsheet with 100 rows, and it took about seven seconds. By using Range.getValues(), the batch version takes one second.
function getFirstEmptyRow() {
var spr = SpreadsheetApp.getActiveSpreadsheet();
var column = spr.getRange('A:A');
var values = column.getValues(); // get all data in one call
var ct = 0;
while ( values[ct][0] != "" ) {
ct++;
}
return (ct);
}
If the spreadsheet gets big enough, you might need to grab the data in chunks of 100 or 1000 rows instead of grabbing the entire column.
It's already there as the getLastRow method on the Sheet.
var firstEmptyRow = SpreadsheetApp.getActiveSpreadsheet().getLastRow() + 1;
Ref https://developers.google.com/apps-script/class_sheet#getLastRow