Anonymous wrote:
We are developing in .net,and using firebird..how do you deal with concurrency issue?
Ann W.Harrison answers:
Typically, people rely on transactions to avoid conflicting updates. Some applications can't keep a transaction open for the time required to identify the target rows, determine how to change them, and make the change. One way to handle that issue is to add a version flag to each record. Use a generator to get a new version number and update the target records with that number when the record is chosen, and commit that transaction. When you're ready to make the real changes, check that the version in the record is still yours.
This process requires considerable discipline - if any transaction changes a record without updating the version number, you've got problems. One way to check for undisciplined updates is to have a trigger that rejects updates where old.version = new.version.
I wouldn't use timestamps - there are just too many opportunities to get a slightly wrong value and confuse the system.