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From: Jocelyn R. <jra...@ua...> - 2013-03-09 16:38:37
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Hi Sedna Team,
Sorry for the long email.
We have been having some serious problem in our production database with
"(SE4703) The transaction is a victim of deadlock resolution procedure."
We have the latest sedna release on Linux Red Hat.
Our situation is as follow:
1. Our main entity is an "Award Competition" which is split into several
smaller entities kept into separate sedna collections.
2. Our smaller entities are: collection('personal-info'),
collection('student-payload'), collection('activity') and so on. Each
entities are quite small (average of 10-20 tags with fairly short text
nodes).
3. So one person applying to one "Award Competition" will need to do a
"write" to all those collections.
4. We also need to "write" all those xml documents in one transaction
(write all or rollback).
5. We know that, in order to write to sedna, the transaction need to
acquire a lock on the "collection" and not the "document".
6. We have thousands of people applying and what we think is happening is
that one person gets the lock for the collection('personal-info') and
another person gets the lock for collection('student-payload') which result
in the deadlock i.e. the first person having the lock for
collection('personal-info'), in the same transaction, is trying to acquire
the lock for collection('student-payload') but can't because it is used by
the second person transaction and vice versa.
The questions are:
1. Is it possible to have sedna locking on document instead of collection?
(probably not but worth to ask).
2. We tried to make our transaction as small as possible but need to "save"
to several collections in one transactions.
3. Any suggestions?
We are in the process to try the XQJ driver but we don't think it will
resolve our deadlock situation. Let me know if you think XQJ may give us
better result.
As such, I have a question in regard using XQJ:
Would this be valid xquery with sedna (we want to "LOAD" a new document):
XQPreparedExpression expression = conn.prepareExpression("declare variable
$collection external; " +
"declare variable
$docname external; " +
"declare variable
$xmldoc external; " +
"UPDATE insert
$xmldoc INTO doc($docname,$collection)";
//
String collection = "activity";
String docname = "unique_name_goes_here";
String xmldoc = "<activity>...</activity>";
// Or Document xmldoc = builder.newDocument()...;
expression.bindDocument(new QName("xmldoc"), xmldoc, null, null); // not
sure of the last two parameters
expression.bindString(new QName("docname"), docname, null, null);
expression.bindString(new QName("collection"), collection, null, null);
The question is "expression.bindDocument(...)" Is it the right thing to do
to LOAD new document or should we use "expression.bindItem(...)" or
"expression.bindSequence(...)" or
"expression.bindNode(...)" or
"expression.bindObject(...)"
Note: We use JAXB. Can we pass JAXB as a "bind???" method?
Entities:
Here is an example of entity model we have for collection('activity')
<activity type="university" id="1360861690701">
<organization-name>female basketball team</organization-name>
<position-title>player</position-title>
<date attending="" end="2012-10-25" start="2012-05-03"/>
<time-commitment-per-week>120</time-commitment-per-week>
<description>This is a sample description that can contain up to 300
words.</description>
</activity>
Thank you very much for your input,
Jocelyn Raymond
--
Data Architect / Development Manager
Information Systems
Office of the Registrar
University of Alberta
780.492.3874
*** Please note: Our unit has moved to SAB-1-26. Other moves will be
happening within the Office of the Registrar over the coming weeks. To keep
updated, please visit our
website<http://www.registrarsoffice.ualberta.ca/Faculty-and-Staff/Office-Move.aspx>.
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