Shuffling an array randomly

There are various ways to do this, but anything you do you'll have to build yourself.

A quick-and-dirty way I just thought of:

1. use a!forEach to loop over the CDT array and use updateDictionary() to add a new ad-hoc property to each one, i.e. "order", set to the value of a rand() call.  This will give a random decimal between 0 and 1 to all items; they should almost always be unique as far as I know.
2. Sort the array based on the "order" decimal (use the "toDataSubseet" trick to sort an array of dictionary based on the value of a property).

There are various ways to do this, but anything you do you'll have to build yourself.

A quick-and-dirty way I just thought of:

1. use a!forEach to loop over the CDT array and use updateDictionary() to add a new ad-hoc property to each one, i.e. "order", set to the value of a rand() call.  This will give a random decimal between 0 and 1 to all items; they should almost always be unique as far as I know.
2. Sort the array based on the "order" decimal (use the "toDataSubseet" trick to sort an array of dictionary based on the value of a property).

Thanks Mike,

This was a really innovative way to sort and shuffle a large array at low perofromance cost. But I feel that since we have the functionality of fetching randomly sorted records direct from SQL query in MySQL, Appian should incorporate a way to use that functionality as it will save a great coding time and performance load will be reduced.

Something like that would need to be built into the a!queryEntity function or one of its components - you could always file a feature request ticket with Appian Support, however I wouldn't expect it to be prioritized anytime soon without a strong use case on your end.

Out of boredom I went ahead and implemented a standalone function where you input the desired number of items and it returns a randomized list of integer indices 1...N, where we're guaranteed to have no duplicates or missing numbers.  This integer array could then be used to index into any particular array in a randomized manner.

a!localVariables(
  
  local!targetSize: 25,
  
  local!dict: a!forEach(
    enumerate(local!targetSize),
    
    a!map(
      integer: fv!index,
      sort: rand()
    )
  ),
  
  local!sorted: todatasubset(
    local!dict,
    a!pagingInfo(
      startIndex: 1, batchSize: -1,
      sort: a!sortInfo(field: "sort", ascending: true())
    )
  ),
  
  local!sorted.data.integer
)