Multiple Users - Tabular Forms - Multi Row Update.....

Question

Greetings All,
Any comments, assistance, links, or even answers on the following situation would be much appreciated....
I have a Application Express 4.0 (Could upgrade to 4.1 if it would help this issue)
I have a wizard generated tabular form on a table, the form will show up to 600 records (rows) on a page.
Part 1:
The situation:
User 1: Opens the form and brings up latest data set.
User 2: Opens the form and brings up the latest data set.
User 1: Changes data for record 1
User 1: Hits submit. The data is saved.
User 2: Changes data for record 1
User 2: Changes data for record 2
User 2: Hits submit. The following error is produced:
Error in mru internal routine: ORA-20001: Error in MRU: row= 1, ORA-20001: ORA-20001: Current version of data in database has changed since user initiated update process. current checksum = "3EE15D666E9DBDC59D34CE4CFB3950C0", item checksum = "922DA12AE1E3D8856695745C4D2830D2"., update "<Removed> Error Unable to process update.
When this error occurs no updates get made to the table.
I understand that row 1 can not be updated, however I would like row 2 (and all other rows where there is no conflict) to be updated. I would then like to be able to highlight in the form the rows that failed to update (And reload the data in them from the DB).
Is this something I can achieve using my own MRU procedure, or in another way?
Can anyone point me to a good example, tutorial or book showing how to do this.
Thanks!

Answer 1

Thanks for the comments guys.
I have solved my issue in two different ways. Way one was not so clever, but worked, involving writing my own process for handling multi-row updates and would allow a user to fill in data for multiple rows (say 10) and have only the row with changed data rejected. V2 takes a very different approach, it uses Javascript, AJAX and the DOM model of the form to check when data is changed / updated by the user. Essentially, when a user enters an updateable form element, a AJAX request checks if the data has been changed. If it has, the value in the form is updated, and the color changed to blue to alert the user. When the user updates the data item, and AJAX request posts the new value to the database, where it is inserted. I had to build a bit of a framework to make this useable, and have to use dynamic sql in the database packages, but it work really well for what my users need! There are limitations (Currently it only supports date fields, text fields and drop down lists) but it works for me. It also involves traffic back and forth with the server each time a user moves the focus to a new form element, but it is a very light request and the work to do the select / updates in oracle is all based on a primary ke, so is ver quick.
Solution 1: (Would need to be made much more elegant):
1: Create a new text Item called P5_MESSAGE (To display error / success messages)
2: Create a new process:
DECLARE
l_cks wwv_flow_global.vc_arr2;
j pls_integer := 1;
vUpdatedCount number := 0;
vErrorCount number:=0;
vMessage varchar2(4000):='';
BEGIN
select wwv_flow_item.md5(firstname,lastname,age) cks
BULK COLLECT INTO
l_cks
from VA_TEST1 ;
for i in 1..l_cks.count
loop
if htmldb_application.g_fcs(i) != l_cks(i) then
-- Log error
vErrorCount:=vErrorCount+1;
vMessage:=vMessage||'Could not update row with ID:' || htmldb_application.g_f01(i) || '. This data has been updated by another user since you retrieved the data.<br>';
else
-- Do insert
vUpdatedCount:=vUpdatedCount+1;
update VA_TEST1
set
FIRSTNAME = replace(htmldb_application.g_f02(i),'%'||'null%',NULL)
,LASTNAME = replace(htmldb_application.g_f03(i),'%'||'null%',NULL)
,AGE = replace(htmldb_application.g_f04(i),'%'||'null%',NULL)
where ID = htmldb_application.g_f01(i);
end if;
end loop;
:P5_MESSAGE := vMessage;
end;
Note, this currently updates every row, even if the data is unchanged, this could be fixed by comparing the checksum of the data to be inserted with the checksum of the data in the table, if the same then no need to insert.
Solution 2:
Too complex to explain in detail here, if you need to implement this then let me know.