Re: Optimistic locking failure on insert
Re: Optimistic locking failure on insert
- Subject: Re: Optimistic locking failure on insert
- From: "Jerry W. Walker" <email@hidden>
- Date: Wed, 15 Mar 2006 10:31:09 -0500
Hi, Ian,
I can't imagine (short of a bug in the development environment) how
the code you're exposing below could cause an optimistic locking
failure. The upshot of the code below only reads from the store. It
neither creates nor updates any records therein.
Optimistic locking failures occur on an attempt to write a record to
the database when the record on the database into which you're trying
to write has data other than what you expected to be there. This is
typically caused by someone else writing into the same record before
you, but can also be caused by rounding errors in fields your
checking for the optimistic locking check (e.g. including Doubles or
Date fields among the optimistic lock check fields).
On Mar 14, 2006, at 11:54 PM, Ian Joyner wrote:
OK, found the problem. It was not in the model, but rather in the
code for initializing a JTree. First, I was getting top-level nodes
by getting them out of the display group:
NSArray notes = EOQualifier.filteredArrayWithQualifier
(display_group.allObjects (),
EOQualifier.qualifierWithQualifierFormat ("parent_note = null",
null));
however, sometimes the display group had not fetched yet, so I used
a fetch spec to go straight to the DB:
NSArray notes = editing_context.objectsWithFetchSpecification (new
EOFetchSpecification ("Note", new EOAndQualifier (new NSArray (new
Object [] {EOQualifier.qualifierWithQualifierFormat ("parent_note =
null", null), EOQualifier.qualifierWithQualifierFormat ("owner = %
@", new NSArray (new Object [] {owning_display_group.selectedObject
()}))})), null));
The above statement is more difficult to read than it needs to be.
You can use "AND" directly in the qualifierWithQualifierFormat method.
For some reason, which I'd like an explanation for, this caused the
optimistic locking problem when creating a new master record. So
then I realised the most straight forward solution was to traverse
the object path:
NSArray notes = EOQualifier.filteredArrayWithQualifier (((Artifact)
owning_display_group.selectedObject ()).notes (),
EOQualifier.qualifierWithQualifierFormat ("parent_note = null",
null));
(The fetch spec code probably would have been better in Haskell,
but I dislike assigning things to temporary variables in Java when
the code could be more functional.)
I generally find that temporary variables can add greatly to the
semantic value of the code. It can make the code significantly more
readable. How does leaving them out make the code more functional?
Don't know if this little note may help anyone in the future,
because I still don't know the link between the fetch spec and the
optimistic locking failure (and I hate the hacking until it happens
to work approach).
In looking over the debugging statements below, it looks like there
is an attempt to save a member record which contains itself as a
member. That is, it looks like the inserted record has the following
recursive structure:
MemberRecord:
details = null
begin_date = 3/14/2006 @ 5:53:51 GMT
position = null
member = <self reference> ************ IS THIS CORRECT?
****************
end_date = null
group = Groups: {
<some not-yet-saved GroupMember>
}
person = null
title = <reference to previously saved title with PK = 1>
telephones = ()
modification_date = 3/14/2006 @ 5:53:51 GMT
I can certainly imagine problems with such a structure, if I'm
inferring correctly.
Have you turned on EOAdaptorDebuggingEnabled to check the generated
SQL? It looks like EOF may be attempting to write a record that
contains itself recursively and determines on the second recursion
that the record has already been written. That would be my guess
without seeing the SQL.
Hope this helps.
Regards,
Jerry
Ian
On 14/03/2006, at 5:09 PM, Ian Joyner wrote:
I have been running this model for six months and saving this
entity just fine. Suddenly, I am getting an optimistic locking
failure when doing an insert of a new record (that's right insert,
not update). In fact is the trace below, I show that the offending
record is in the editing contexts insertedObjects and it has a
EOTemporaryGlobalID which means it has not been written to the
database yet.
No SQL commands are being executed in the SQL trace. I have turned
off locking on every attribute for this entity in EOModeler. Other
entities are still saving fine. So what's going on? How can I get
around this problem?
[2006-03-14 16:53:56 EST] <AWT-EventQueue-0>
xxx.client.Member_interface_controller save inserted ({values =
{details = <com.webobjects.foundation.NSKeyValueCoding$Null>;
begin_date = 2006-03-14 05:53:51 Etc/GMT; position =
<com.webobjects.foundation.NSKeyValueCoding$Null>; member =
"<com.sportstec.member.client.Member f1156e <EOTemporaryGlobalID:
0 0 -64 -88 0 7 0 0 -15 83 1 0 0 0 1 9 -9 81 65 -102 58 -107 -26
-116>>"; end_date = <com.webobjects.foundation.NSKeyValueCoding
$Null>; group = "<com.sportstec.group.client.Group 47545b groups
= ("<com.sportstec.group.client.Group_Member 8dacbb
<EOTemporaryGlobalID: 0 0 -64 -88 0 7 0 0 -15 83 2 0 0 0 1 9 -9 81
65 -102 58 -107 -26 -116>>"); person = "null"; title =
"<com.webobjects.eocontrol.EOGenericRecord dd1d62
_EOIntegralKeyGlobalID[Title (java.lang.Integer)1]>"; telephones =
(); modification_date = 2006-03-14 05:53:51 Etc/GMT; }; this =
"<com.sportstec.member.client.Member f1156e <EOTemporaryGlobalID:
0 0 -64 -88 0 7 0 0 -15 83 1 0 0 0 1 9 -9 81 65 -102 58 -107 -26
-116>>"; })
[2006-03-14 16:53:56 EST] <AWT-EventQueue-0>
xxx.client.Member_interface_controller save updated (Gq)
[2006-03-14 16:53:56 EST] <AWT-EventQueue-0>
xxx.client.Member_interface_controller save deleted ()
[2006-03-14 16:53:56 EST] <AWT-EventQueue-0>
xxx.client.Member_interface_controller EditingContext saveChanges
failed Server exception: Optimistic locking failure: The object
with global ID <EOTemporaryGlobalID: 0 0 -64 -88 0 7 0 0 -15 83 1
0 0 0 1 9 -9 81 65 -102 58 -107 -26 -116> has been changed by
another client
Thanks
Ian Joyner
Sportstec
--
__ Jerry W. Walker,
WebObjects Developer/Instructor for High Performance Industrial
Strength Internet Enabled Systems
email@hidden
203 278-4085 office
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