Oh, wow. Looks great Andy. Thanks for suggestion.

Wonder to know what's Christian's opinion on this.

M.

On 07/02/25 16:45, Andy Bunce wrote:

>so if you call store:get, store:put or store:write in the first process, a second process will not wait until the store operations are completed.

In non XQuery contexts a semaphore [1] might be used to ensure that my other threads don't get between a get and put.

In the spirit of blurring the XQuery Java boundaries I tried [2]. It seems to work. Is it dangerous?

[1] https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/Semaphore.html 

[2]

declare namespace Semphore ="java:java.util.concurrent.Semaphore";

declare  function local:config-update($k as xs:string,$v as item(),$sem) {
   Semphore:acquire($sem),
   try{
     let $u:=store:get("config")=> map:put($k, $v)
     return store:put("config",$u)
   }catch * {
     trace("Errrr",$err:description)
   }
   ,Semphore:release($sem)
};

let $sem:=Semphore:new(1,true())

let $s1 := store:put("config", map{})
let $s2 := xquery:fork-join(
  for $i in (1 to 100)
  return function(){
    let $r:=(prof:sleep(10),$i)
    return local:config-update( string($i),$r,$sem) }
  )

return count(map:keys(store:get("config")))

On Tue, 28 Jan 2025 at 14:09, Marco Lettere <m.lettere@gmail.com> wrote:

Ok, thanks for the clarification.

M.

On 28/01/25 15:08, Christian Grün wrote:

Sorry Christian, do you mean *not* synchronized?

With »synchronized«, I meant to refer to a lower level: You will not end up with a corrupt key/value store or with I/O conflicts when accessing and updating the store via multiple threads. However, as you have already observed, multiple operations are not executed in a well-defined order, so if you call store:get, store:put or store:write in the first process, a second process will not wait until the store operations are completed.