[basex-talk] tail recursion issue in 9.4.3

[Mark McSweeny]

Hello,

I have encountered a difference in behaviour between versions 9.3.3 and 
9.4.3 for a certain query involving tail recursion.  In 9.3.3 the 
compiled query plan correctly applied tail call optimization.  But in 
9.4.3 tail call optimization is not applied, resulting in a stack 
overflow during execution.

Here is a minimal query that demonstrates the issue:


declare function local:f($n, $xs)
{
  if ($n = 0) then $xs
  else
    let $x :=
      copy $node := <a/> modify ( rename node $node as 'x') return $node
    return local:f($n - 1, ($xs, $x))
};
local:f(2000, ())



Mark