intermittent transaction failure caused by internal duplicate savepoint name,
for tirgger
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Key: DERBY-3093
URL: https://issues.apache.org/jira/browse/DERBY-3093
Project: Derby
Issue Type: Bug
Affects Versions: 10.3.1.4
Environment: Java 1.6.0_02
Reporter: Jim Newsham
While running our app overnight, performing some intensive database operations
(primarily deletes), we experienced a transaction failure, with error message
"A SAVEPOINT with the passed name already exists in the current transaction".
This failure appears to be very intermittent, as I've run the same operation
successfully for hours and hours without failure. Some more information:
1. I see that there are four JIRA issues which report the same message
(DERBY-2773, DERBY-1457, DERBY-2808, DERBY-2804). I am not sure to what extent
if any, the problem I experienced is related to these issues.
• At least three of the above JIRA issues are related to triggers. Our
transaction failure occurred while performing a delete in a table which has
delete triggers.
• We aren't using savepoints explicitly. Of course, it can be seen in
the stack trace that the trigger operation is setting a savepoint.
• One of the JIRA issues mentions exceeding maximum depth of nested
triggers. Not sure what a nested trigger is, but the trigger we are performing
should not (in theory) cause another trigger event.
2. Here's the stack trace:
Caused by: java.sql.SQLException: A SAVEPOINT with the passed name already
exists in the current transaction.
at
org.apache.derby.impl.jdbc.SQLExceptionFactory40.getSQLException(Unknown Source)
at org.apache.derby.impl.jdbc.Util.generateCsSQLException(Unknown
Source)
at
org.apache.derby.impl.jdbc.TransactionResourceImpl.wrapInSQLException(Unknown
Source)
at
org.apache.derby.impl.jdbc.TransactionResourceImpl.handleException(Unknown
Source)
at org.apache.derby.impl.jdbc.EmbedConnection.handleException(Unknown
Source)
at org.apache.derby.impl.jdbc.ConnectionChild.handleException(Unknown
Source)
at org.apache.derby.impl.jdbc.EmbedStatement.executeStatement(Unknown
Source)
at
org.apache.derby.impl.jdbc.EmbedPreparedStatement.executeStatement(Unknown
Source)
at
org.apache.derby.impl.jdbc.EmbedPreparedStatement.executeUpdate(Unknown Source)
at
com.referentia.sdf.monitor.samplebase.derby.DerbySampleBase$3.perform(DerbySampleBase.java:682)
at
com.referentia.sdf.monitor.samplebase.derby.DerbySampleBase.performInTransaction(DerbySampleBase.java:2747)
... 7 more
Caused by: java.sql.SQLException: A SAVEPOINT with the passed name already
exists in the current transaction.
at
org.apache.derby.impl.jdbc.SQLExceptionFactory.getSQLException(Unknown Source)
at
org.apache.derby.impl.jdbc.SQLExceptionFactory40.wrapArgsForTransportAcrossDRDA(Unknown
Source)
... 18 more
Caused by: ERROR 3B501: A SAVEPOINT with the passed name already exists in the
current transaction.
at org.apache.derby.iapi.error.StandardException.newException(Unknown
Source)
at org.apache.derby.impl.store.raw.xact.Xact.setSavePoint(Unknown
Source)
at
org.apache.derby.impl.store.access.RAMTransaction.setSavePoint(Unknown Source)
at
org.apache.derby.impl.sql.conn.GenericStatementContext.setSavePoint(Unknown
Source)
at org.apache.derby.impl.sql.GenericPreparedStatement.execute(Unknown
Source)
at
org.apache.derby.impl.sql.execute.GenericTriggerExecutor.executeSPS(Unknown
Source)
at
org.apache.derby.impl.sql.execute.RowTriggerExecutor.fireTrigger(Unknown Source)
at
org.apache.derby.impl.sql.execute.TriggerEventActivator.notifyEvent(Unknown
Source)
at
org.apache.derby.impl.sql.execute.DeleteResultSet.fireAfterTriggers(Unknown
Source)
at org.apache.derby.impl.sql.execute.DeleteResultSet.open(Unknown
Source)
at org.apache.derby.impl.sql.GenericPreparedStatement.execute(Unknown
Source)
... 12 more
3. Here are the relevant tables and triggers. We have different tables for
different "sample" data types in our application (currently int, long, float,
double, Boolean, string). I have shown the int_sample table; the other tables
are identical but have a different data type for the value field.
Sample records are first class; time records are second class - they only exist
to support sample records. When there are no remaining sample records for a
given time record, the time record can be removed. It is the job of the
trigger to perform this cleanup: when a record is deleted from any of the
sample tables, the time record corresponding to *_sample.fk_time_id is deleted
only if there are no remaining records in any of the sample tables which have
the same fk_time_id. So although there are cascading deletes (deleting a time
record deletes all of its samples), the trigger should not recurse because the
trigger only deletes when there are no associated records.
create table time (
id int not null generated always as identity,
time timestamp not null,
constraint time_pk primary key (id),
constraint time_unique unique (time)
);
create table int_sample (
fk_band_id int not null,
fk_time_id int not null,
value int not null,
constraint int_sample_pk primary key (fk_band_id, fk_time_id),
constraint int_sample_fk_band foreign key (fk_band_id) references band (id)
on delete cascade,
constraint int_sample_fk_time foreign key (fk_time_id) references time (id)
on delete cascade
);
create trigger cascade_delete_unused_time_for_int_sample_trigger
after delete on int_sample
referencing old as oldrow
for each row
delete from time where
time.id = oldrow.fk_time_id
and id not in (select fk_time_id from int_sample)
and id not in (select fk_time_id from long_sample)
and id not in (select fk_time_id from float_sample)
and id not in (select fk_time_id from double_sample)
and id not in (select fk_time_id from boolean_sample)
and id not in (select fk_time_id from string_sample);
4. Invocation. This is very rough pseudocode focusing on the core logic. In
reality, there's a lot more code, but I'm doing the usual stuff, such as using
prepared statements, and closing all resources when done. The key thing is
that I'm using two statements in a nested fashion; in the outer statement, I
iterate over records in the time table, and in the inner loop I use a second
statement to delete records in one of the sample tables. I can provide the
actual code if desired.
deleteSamples(int bandId, String sampleTable, Object someQueryCriteria) {
within transaction {
create stmt1 iterating over time ids in time table (restricted by
someQueryCriteria)
for (time_id in stmt1) {
PreparedStatement stmt2 = conn.prepareStatement(String.format(
"delete from %s where fk_band_id = ? and fk_time_id = ?", sampleTable));
set stmt2 parameters and executeUpdate()
}
}
}
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