Hi Eric,
I am not sure that I am following this correctly, so some questions below.
On Dec 2, 2005, at 8:26 AM, Eric Stewart wrote:
Hello everyone,
I'm having a problem where it appears I'm getting stale data from the
editing context.
I have a direct action that is inserting keywords into a database
table. The word itself (called "descriptor") is unique because I don't
want the same keyword in the system twice.
When a direct action request comes in for information about that
keyword, I check to see if that keyword is already in the system. If
not I add it.
Here is the code I use to check for that keyword.
/**
* Determines whether a new keyword with the given descriptor is
present in the system.
*/
public static boolean isPresentByDescriptor(EOEditingContext ec,
String descriptor) {
NSDictionary args = new NSDictionary(descriptor, "descriptor");
EOQualifier qual = EOQualifier.qualifierToMatchAllValues(args);
EOFetchSpecification fs = new EOFetchSpecification("NewKeyword", qual, null);
// Make sure we fetch fresh data
fs.setRefreshesRefetchedObjects(true);
// Find the keyword matching value
NSArray keywords = ec.objectsWithFetchSpecification(fs);
if (keywords.count() == 0) {
// No match found
return false;
} else if (keywords.count() > 1) {
// More than one match found
if (NSLog.debugLoggingAllowedForLevel(NSLog.DebugLevelCritical)) {
NSLog.debug.appendln("Duplicate new keyword found matching: " + descriptor);
}
return true;
} else {
// Match found return the keyword
return true;
}
}
What is happening is I'm getting a lot of exceptions complaining that
a keyword being added to the system is not unique, hence I can only
guess that data from the EC is stale and is not reflecting newly
inserted keywords.
By exception do you mean the debug message above, a unique constraint violation on the database, or something else?
This direct action is running on an application that has around 20
instances running. So some how one of the other instances is inserting
a new keyword and the other instances continue to report it as not
being there.
You could have a race condition where two instances check the database for the same keyword, and see that it is not there. They they both insert it. The second one to commit will (attempt to) duplicate the value in the database. Is that what you are seeing? You can even see this on a single instance if you are dispatching requests concurrently.
Should I be using EditingContext.refaultAllObjects() or will this not
solve my problem. What I don't want to happen is for this to severely
degrade the performance of the application. I think I remember
EditingContext.invalidateAllObjects() causing a pretty poor
performance on high load applications, which this is. Is there some
other way to check whether the keyword is in the system or not before
it's added without incurring such a severe penalty?
I would not suggest any of those solutions. Are the instances actually changing the descriptor of NewKeywords, just only inserting new ones? If they are only inserting new ones, there should not be an issue with actual stale data the way you are fetching it. I suspect your problem may lie elsewhere.
Is there anyway to refault JUST the data in a certain table or of a
certain type of EO and not all the data in an EditingContext.
You can do it object by object, but again, that does not seem to be the problem (or I am misunderstanding your situation).
Chuck
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