On Jun 11, 2021, at 11:08 AM, OCsite <webobjects-dev@wocommunity.org> wrote:

P.P.S. It actually does look like the weird cancelled fetch was somehow affected by the background task; upon further investigation of the case

On 11. 6. 2021, at 15:20, OCsite <webobjects-dev@wocommunity.org> wrote:

===

15:05:48.528 DEBUG  === Begin Internal Transaction       //log:NSLog [WorkerThread5]

15:05:48.528 DEBUG  evaluateExpression: <com.webobjects.jdbcadaptor.FrontbasePlugIn$FrontbaseExpression: "SELECT ... t0."C_UID", ... FROM "T_RECORD" t0 WHERE t0."C_IMPORT_ID" = 1003547" withBindings: >       //log:NSLog [WorkerThread5]

15:05:49.937 DEBUG fetch canceled       //log:NSLog [WorkerThread5]

15:05:49.937 DEBUG 164 row(s) processed       //log:NSLog [WorkerThread5]

15:05:49.941 DEBUG  === Commit Internal Transaction       //log:NSLog [WorkerThread5]

15:05:49.941 INFO  Database Exception occured: java.lang.IllegalArgumentException: Cannot determine primary key for entity DBRecord from row: {... uid = <com.webobjects.foundation.NSKeyValueCoding$Null>; ... }       //log:er.transaction.adaptor.Exceptions [WorkerThread5]

===

I've found that concurrently a background fetch did run, and essentially at the same time — just couple of hundreds of second later — was cancelled, too:

===

15:05:47.355 DEBUG  === Begin Internal Transaction       //log:NSLog [MainPageSlaveRowsCountThread_Cizí nákupy EB]

15:05:47.355 DEBUG  evaluateExpression: <com.webobjects.jdbcadaptor.FrontbasePlugIn$FrontbaseExpression: "SELECT count(*) FROM "T_RECORD" t0, "T_IMPORT" T1, "T_IMPORT" T3, "T_RECORD" T2 WHERE (t0."C_OWNER__ID" is NULL AND T3."C_DATA_BLOCK_ID" = 1000387) AND t0."C_IMPORT_ID" = T1."C_UID" AND T2."C_IMPORT_ID" = T3."C_UID" AND T1."C_OWNER_RECORD_ID" = T2."C_UID"" withBindings: >       //log:NSLog [MainPageSlaveRowsCountThread_Cizí nákupy EB]

15:05:49.973 DEBUG fetch canceled       //log:NSLog [MainPageSlaveRowsCountThread_Cizí nákupy EB]

15:05:49.975 DEBUG 1 row(s) processed       //log:NSLog [MainPageSlaveRowsCountThread_Cizí nákupy EB]

15:05:49.983 DEBUG  === Commit Internal Transaction       //log:NSLog [MainPageSlaveRowsCountThread_Cizí nákupy EB]

===

Note it runs over a different OSC, but still — might this be the culprit? Would EOF somehow cancel a fetch if two of them happen in the same moment, albeit both of them happen in different ECs over a different OSC?

I do not lock here, for there is absolutely no danger more threads would use the same EC concurrently (though more different background threads could use concurrently ECs over same OSC). I thought it is all right in this case. Is it not? Should I try to lock those ECs or even the OSC?

Thanks,

OC

Any idea what might go wrong and how to fix it? Thanks!

OC

On 11. 6. 2021, at 13:37, OCsite <webobjects-dev@wocommunity.org> wrote:

Hi there,

just bumped into another weird EOF case. A pretty plain fetch caused a “Cannot determine primary key for entity” exception. The row contains a number of columns whose values makes sense, some null, some non-null, with one exception — the primary key, modelled as an attribute uid, is indeed a null, thus the exception makes a perfect sense.

How can this happen?

===

IllegalArgumentException: Cannot determine primary key for entity DBRecord from row: {... uid = <com.webobjects.foundation.NSKeyValueCoding$Null>; ... }

  at com.webobjects.eoaccess.EODatabaseChannel._fetchObject(EODatabaseChannel.java:348)

     ... skipped 2 stack elements

  at com.webobjects.eocontrol.EOObjectStoreCoordinator.objectsWithFetchSpecification(EOObjectStoreCoordinator.java:488)

  at com.webobjects.eocontrol.EOEditingContext.objectsWithFetchSpecification(EOEditingContext.java:4069)

  at er.extensions.eof.ERXEC.objectsWithFetchSpecification(ERXEC.java:1215)

     ... skipped 1 stack elements

  at com.webobjects.eocontrol.EOObjectStoreCoordinator.objectsForSourceGlobalID(EOObjectStoreCoordinator.java:634)

  at com.webobjects.eocontrol.EOEditingContext.objectsForSourceGlobalID(EOEditingContext.java:3923)

  at er.extensions.eof.ERXEC.objectsForSourceGlobalID(ERXEC.java:1178)

     ... skipped 1 stack elements

  at com.webobjects.eoaccess.EOAccessArrayFaultHandler.completeInitializationOfObject(EOAccessArrayFaultHandler.java:77)

  at com.webobjects.eocontrol._EOCheapCopyMutableArray.willRead(_EOCheapCopyMutableArray.java:45)

  at com.webobjects.eocontrol._EOCheapCopyMutableArray.count(_EOCheapCopyMutableArray.java:103)

  at com.webobjects.foundation.NSArray.isEmpty(NSArray.java:1888)

...

===

Just in case it happens to be important (I believe it is not), the problem happens at row

        ... =eolist.representedObject.records().isEmpty()?...:...

where records just returns storedValueForKey('records'), self-evidently a fault, which fires to fetch the rows.

Searching the Web, all I've found is this (linked from here), which does not really help :) Truth is, some background threads do run at the moment; they are comparatively plain though and I can't see why they should cause the problem for the R/R thread. All they do is to

1. get their own OSC from the pool, making sure they never get the same OSC normal sessions have

2. create a new ERXEC in this OSC

3. get a local instance of an object in the EC

=== this is the code of the background thread; a number of those runs:

        def store

        for (def pool=ERXObjectStoreCoordinatorPool._pool();;) {

            store=pool.nextObjectStore

            if (store!=_sessionosc) break // there's one OSC for all sessions, stored in _sessionosc

        }

        return eo.localInstanceIn(ERXEC.newEditingContext(store)).numberOfMasterRowsWithoutOwner()

===

and the method simply fetches:

===

    int numberOfMasterRowsWithoutOwner {

        def mymasterrow=EOQualifier.qualifierWithQualifierFormat("importObject.dataBlock = %@ AND recordOwner = NULL",[this] as NSA)

        return ERXEOControlUtilities.objectCountWithQualifier(this.editingContext, 'DBRecord', mymasterrow)

    }

===

Most time it works properly. Occasionally — rather rarely — the problem above happens. Can you see what am I doing wrong?

Thanks a lot,

OC