Hello, all:
Derby is used heavily in my project and its tables are frequently accessed
concurrently by multiple threads. Some threads update one or several tables,
while other threads perform run select statements against those. I've written
to this group several times whenever errors occurred, but some of those message
have either been ignored or contained references to fairly short explanations
on the website. So, the problems continue and it is difficult to find the
proper solution.
All problems happen due to the concurrent access to tables. For instance,
today's problem had to do with one thread updating one table (the table is
first truncated and then re-populated to stay in sync with the source of data),
while the other thread was trying to create a PreparedStatement. So, while one
thread was truncating a table, another threw this exception (probably caused by
nested select statements):
java.sql.SQLException: The conglomerate (1,280) requested does not exist.
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.EmbedPreparedStatement.<init>(Unknown
Source)
at org.apache.derby.impl.jdbc.EmbedPreparedStatement20.<init>(Unknown
Source)
at org.apache.derby.impl.jdbc.EmbedPreparedStatement30.<init>(Unknown
Source)
at org.apache.derby.impl.jdbc.EmbedPreparedStatement40.<init>(Unknown
Source)
at org.apache.derby.jdbc.Driver40.newEmbedPreparedStatement(Unknown
Source)
at org.apache.derby.impl.jdbc.EmbedConnection.prepareStatement(Unknown
Source)
at org.apache.derby.impl.jdbc.EmbedConnection.prepareStatement(Unknown
Source)
at
com.jefco.fi.commons.database.SqlSyntaxStatement.<init>(SqlSyntaxStatement.java:76)
at
com.jefco.fi.commons.database.SqlSyntaxStatement.<init>(SqlSyntaxStatement.java:44)
...
Caused by: java.sql.SQLException: The conglomerate (1,280) requested does not
exist.
at
org.apache.derby.impl.jdbc.SQLExceptionFactory.getSQLException(Unknown Source)
at
org.apache.derby.impl.jdbc.SQLExceptionFactory40.wrapArgsForTransportAcrossDRDA(Unknown
Source)
... 19 more
Caused by: ERROR XSAI2: The conglomerate (1,280) requested does not exist.
at org.apache.derby.iapi.error.StandardException.newException(Unknown
Source)
at
org.apache.derby.impl.store.access.heap.HeapConglomerateFactory.readConglomerate(Unknown
Source)
at
org.apache.derby.impl.store.access.RAMAccessManager.conglomCacheFind(Unknown
Source)
at
org.apache.derby.impl.store.access.RAMTransaction.findExistingConglomerate(Unknown
Source)
at
org.apache.derby.impl.store.access.RAMTransaction.getStaticCompiledConglomInfo(Unknown
Source)
at
org.apache.derby.impl.sql.compile.BaseJoinStrategy.fillInScanArgs1(Unknown
Source)
at
org.apache.derby.impl.sql.compile.HashJoinStrategy.getScanArgs(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.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.GroupByNode.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.SubqueryNode.generateExpression(Unknown
Source)
at
org.apache.derby.impl.sql.compile.BinaryOperatorNode.generateExpression(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.UnionNode.generate(Unknown Source)
at
org.apache.derby.impl.sql.compile.NormalizeResultSetNode.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.DistinctNode.generate(Unknown
Source)
at org.apache.derby.impl.sql.compile.UnionNode.generate(Unknown Source)
at
org.apache.derby.impl.sql.compile.NormalizeResultSetNode.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.DistinctNode.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.conn.GenericLanguageConnectionContext.prepareInternalStatement(Unknown
Source)
... 13 more
Sometimes I get these:
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.execute(Unknown
Source)
at
com.jefco.fi.commons.database.SqlSyntaxStatement.execute(SqlSyntaxStatement.java:296)
at
com.jefco.fi.commons.database.DatabaseTable.truncate(DatabaseTable.java:547)
...
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)
... 14 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.ContainerLocking3.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.execute.DDLConstantAction.lockTableForDDL(Unknown
Source)
at
org.apache.derby.impl.sql.execute.AlterTableConstantAction.executeConstantActionBody(Unknown
Source)
at
org.apache.derby.impl.sql.execute.AlterTableConstantAction.executeConstantAction(Unknown
Source)
at org.apache.derby.impl.sql.execute.MiscResultSet.open(Unknown Source)
at
org.apache.derby.impl.sql.GenericPreparedStatement.executeStmt(Unknown Source)
at org.apache.derby.impl.sql.GenericPreparedStatement.execute(Unknown
Source)
Sometimes it takes an extraordinary long time to walk through the ResultSet
(literally each next() takes several minutes).
I must resolve all these errors ASAP and I would like to ask some guidance as
to how to do it most properly. I don't think that writing my own synchronizing
or locking algorithms is the right way to go.
Perhaps you could recommend some books (on Derby or even general DB) which
discuss well and in detail all the locking mechanisms and proper way of
interfacing Java with a database in an environment with a highly and frequently
concurrent access to the tables.
Any of your help would be greatly appreciated,
Regards,
Pavel.
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