Hello

sometime i need to lock for a while a record.
For example, a table of invoice, and a table of line of invoice.

When a user want to modify lines of an invoice, i lock the invoice against
write/delete while the user take time to modify lines.
and if another user want to modify the same invoice, he get a nice message
like "this invoice is beeing modified by another user"

I can use "begin; select * from invoice where idinvoice=x for update" before
letting the user modifying lines.
but if another user come for the same invoice, he got a big timeout.
is there a way to just test if a row a locked to avoid the timeout ?