Mark,
The best solution is to think about the problem as a single transaction:
don't attempt to emulate dirty reads. In the developer training, we talk
about this issue when discussing updates, and show its use in the
implementation of a persistent FIFO queue.
Untested code...
let $doc-root := doc($uri)/root
let $user-element as element()? := $doc-root/[EMAIL PROTECTED] eq $user]
let $new-child := element new-child { 1234 }
let $new :=
if (not($user-element)) then element child {
attribute user { $user },
$new-child
}
else element { node-name($user-element) } {
$user-element/@*,
$user-element/node(),
$new-child
}
return
if ($doc-root) then xdmp:node-insert-child($doc-root, $new)
else xdmp:document-insert($uri, element root { $new })
-- Mike
Mark Boyd wrote:
Can anyone provide suggestions on how to restructure a module to avoid
undetectable deadlocks as outlined in section 4 of the developer's guide?
Specifically, how can I:
1) Create a document if it isn't already found in the database
2) Create a user specific element if it doesn't already exist for the user
in that document
3) Add a child element to the user element in that document if such a
child element does not already exist
4) Update an existing child element if it does exist
I attempted to use eval statements to ensure visibility along the way but ended
up with deadlocks. What strategy should I follow restructuring this code to
avoid such deadlocks?
Thanks.
Mark
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