Hi Christian,

Thank you for this explanation. 

Based on your explanation, having try/catch around db:drop or any updating expression is not able to catch an error because the actual update is performed later. It may be just as well to remove the try/catch around db:drop.

I encountered this specific error using BaseX GUI by running this script while a database was open. 

I was trying to reproduce a problem where this query (and a simplified version of it) got hung up trying to cleanup databases after BaseX gave out of memory errors. I haven't been able to identify what caused the original problem. I suspect that one of the (dozens of) databases got corrupted and even db:list() was not working. 

If db:list() is not working, is there any way to identify which databases might be corrupt, locked, or somehow causing a problem?

Best regards,
Vincent

_____________________________________________

Vincent M. Lizzi

Head of Information Standards | Taylor & Francis Group

vincent.lizzi@taylorandfrancis.com

Time zone: US Eastern  
Book time to meet with me


From: Christian Grün <cg@basex.org>
Sent: Saturday, September 27, 2025 3:05 AM
To: Lizzi, Vincent <Vincent.Lizzi@taylorandfrancis.com>; Christian Grün via BaseX-Talk <basex-talk@mailman.uni-konstanz.de>
Subject: Re: db:drop error not being caught

Hi Vincent, 

Database updates are not immediately processed, but added to the so-called PUL (pending update list) [1] and executed at the very end of the query. When the updates are executed. This means that try/catch won’t have any effect, as the mere addition of the operation to the PUL does not raise any errors.

The interesting question is why the error is raised at all. Do you have multiple independent instances of BaseX that access the same databases? If not, can you imagine an example that allows us to reproduce the behavior?

Best,
Christian

[1] https://docs.basex.org/main/Updates#pending_update_list

Von: Lizzi, Vincent via BaseX-Talk <basex-talk@mailman.uni-konstanz.de>
Gesendet: Donnerstag, September 25, 2025 9:15:45 PM
An: Christian Grün via BaseX-Talk <basex-talk@mailman.uni-konstanz.de>
Betreff: [basex-talk] db:drop error not being caught

Hi all,

I have a query that is intended to delete outdated databases. This has been working but I recently found that if a database is locked the process stops with an error such as:

[db:lock] Database 'name' cannot be updated, it is opened by another process.

As a result, the process is stopped by any database being in a locked state. I would have thought that the try / catch around db:drop would catch the error and allow the process to skip over any locked databases. 

declare variable $age external := 'PT1M'; (: age 1 minute for testing :)

let $cutoff := current-dateTime() - xs:dayTimeDuration($age)
let $databases := db:list-details()[xs:dateTime(@modified-date) lt $cutoff]
return (
  admin:write-log('cleanup delete items older than ' || $cutoff),
  for $db in $databases return (
    admin:write-log('cleanup deleting database ' || $db),
    try {
      db:drop($db)
    } catch * {
      admin:write-log('cleanup error deleting ' || $db || ': ' || $err:description, 'ERROR')
    }
  )
) 


I tried replacing catch * with catch db:open to catch the specific error, but that hasn't helped. 

Why is the error not caught, and is there a better way to write this query to avoid this problem?

Thanks,
Vincent

______________________________________________

Vincent M. Lizzi

Head of Information Standards | Taylor & Francis Group

E-Mail: vincent.lizzi@taylorandfrancis.com

Web: www.tandfonline.com

Time zone: US Eastern

 

Taylor & Francis is a trading name of Informa UK Limited,

registered in England under no. 1072954

 

"Everything should be made as simple as possible, but not simpler."

  


Information Classification: General