[
https://issues.apache.org/jira/browse/DERBY-4279?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12722088#action_12722088
]
Jeff Stuckman commented on DERBY-4279:
--------------------------------------
Output from test case:
Invalidating the prepared statements...
Table locked.
Executing query 1. Query should block because other thread has lock.
Executing query 2. Query should not block because this thread already has the
necessary locks.
java.sql.SQLTransactionRollbackException: A lock could not be obtained within
the time requested
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.executeQuery(Unknown Source)
at Derby4279$Thread2.run(Derby4279.java:81)
at java.lang.Thread.run(Thread.java:619)
Caused by: java.sql.SQLException: A lock could not be obtained within the time
requested
at
org.apache.derby.impl.jdbc.SQLExceptionFactory.getSQLException(Unknown Source)
at
org.apache.derby.impl.jdbc.SQLExceptionFactory40.wrapArgsForTransportAcrossDRDA(Unknown
Source)
... 11 more
Caused by: ERROR 40XL1: A lock could not be obtained within the time requested
at org.apache.derby.iapi.error.StandardException.newException(Unknown
Source)
at
org.apache.derby.impl.services.locks.ConcurrentLockSet.lockObject(Unknown
Source)
at org.apache.derby.impl.services.locks.AbstractPool.lockObject(Unknown
Source)
at
org.apache.derby.impl.services.locks.ConcurrentPool.lockObject(Unknown Source)
at
org.apache.derby.impl.store.raw.xact.RowLocking2.lockContainer(Unknown Source)
at
org.apache.derby.impl.store.raw.data.BaseContainerHandle.useContainer(Unknown
Source)
at
org.apache.derby.impl.store.raw.data.BaseDataFileFactory.openContainer(Unknown
Source)
at
org.apache.derby.impl.store.raw.data.BaseDataFileFactory.openContainer(Unknown
Source)
at org.apache.derby.impl.store.raw.xact.Xact.openContainer(Unknown
Source)
at
org.apache.derby.impl.store.access.conglomerate.OpenConglomerate.init(Unknown
Source)
at org.apache.derby.impl.store.access.heap.Heap.open(Unknown Source)
at
org.apache.derby.impl.store.access.RAMTransaction.openConglomerate(Unknown
Source)
at
org.apache.derby.impl.store.access.RAMTransaction.openConglomerate(Unknown
Source)
at
org.apache.derby.impl.sql.compile.ResultColumnList.generateHolderMethod(Unknown
Source)
at
org.apache.derby.impl.sql.compile.FromBaseTable.getScanArguments(Unknown Source)
at
org.apache.derby.impl.sql.compile.FromBaseTable.generateResultSet(Unknown
Source)
at org.apache.derby.impl.sql.compile.FromBaseTable.generate(Unknown
Source)
at
org.apache.derby.impl.sql.compile.IndexToBaseRowNode.generate(Unknown Source)
at
org.apache.derby.impl.sql.compile.ProjectRestrictNode.generateMinion(Unknown
Source)
at
org.apache.derby.impl.sql.compile.ProjectRestrictNode.generate(Unknown Source)
at
org.apache.derby.impl.sql.compile.ProjectRestrictNode.generateMinion(Unknown
Source)
at
org.apache.derby.impl.sql.compile.ProjectRestrictNode.generate(Unknown Source)
at
org.apache.derby.impl.sql.compile.ScrollInsensitiveResultSetNode.generate(Unknown
Source)
at org.apache.derby.impl.sql.compile.CursorNode.generate(Unknown Source)
at org.apache.derby.impl.sql.compile.StatementNode.generate(Unknown
Source)
at org.apache.derby.impl.sql.GenericStatement.prepMinion(Unknown Source)
at org.apache.derby.impl.sql.GenericStatement.prepare(Unknown Source)
at org.apache.derby.impl.sql.GenericPreparedStatement.rePrepare(Unknown
Source)
... 5 more
Query 2 finished.
> Statement cache deadlock
> ------------------------
>
> Key: DERBY-4279
> URL: https://issues.apache.org/jira/browse/DERBY-4279
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.5.1.1
> Environment: Windows Vista
> Reporter: Jeff Stuckman
>
> Due to a design flaw in the statement cache, a deadlock can occur if a
> prepared statement becomes out-of-date.
> I will illustrate this with the following example:
> The application is using the embedded Derby driver. The application has two
> threads, and each thread uses its own connection.
> There is a table named MYTABLE with column MYCOLUMN.
> 1. A thread prepares and executes the query SELECT MYCOLUMN FROM MYTABLE. The
> prepared statement is stored in the statement cache (see
> org.apache.derby.impl.sql.GenericStatement for this logic)
> 2. After some time, the prepared statement becomes invalid or out-of-date for
> some reason (see org.apache.derby.impl.sql.GenericPreparedStatement)
> 3. Thread 1 begins a transaction and executes LOCK TABLE MYTABLE IN EXCLUSIVE
> MODE
> 4. Thread 2 begins a transaction and executes SELECT MYCOLUMN FROM MYTABLE.
> The statement is in the statement cache but it is out-of-date. The thread
> begins to recompile the statement. To compile the statement, the thread needs
> a shared lock on MYTABLE. Thread 1 already has an exclusive lock on MYTABLE.
> Thread 2 waits.
> 5. Thread 1 executes SELECT MYCOLUMN FROM MYTABLE. The statement is in the
> statement cache but it is being compiled. Thread 1 waits on the statement's
> monitor.
> 6. We have a deadlock. Derby eventually detects a lock timeout, but the error
> message is not descriptive. The stacks at the time of the deadlock are:
> This deadlock is unique because it can still occur in a properly designed
> database. You are only safe if all of your transactions are very simple and
> cannot be interleaved in a sequence that causes the deadlock, or if your
> particular statements do not require a table lock to compile. (For the sake
> of simplicity, I used LOCK TABLE in my example, but any UPDATE statement
> would fit.)
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