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Posted to derby-dev@db.apache.org by "Knut Anders Hatlen (JIRA)" <ji...@apache.org> on 2008/05/29 14:26:45 UTC
[jira] Updated: (DERBY-3693) Deadlocks accessing DB metadata
[ https://issues.apache.org/jira/browse/DERBY-3693?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Knut Anders Hatlen updated DERBY-3693:
--------------------------------------
Attachment: deadlock.diff
It's just a guess, but perhaps the attached patch deadlock.diff solves the problem. Stored prepared statements (which are used for the meta-data queries) are compiled in a nested transaction so that locks on system tables can be released before the main transaction is completed. If the main transaction already has a lock on something the nested transaction also needs to lock, the nested transaction may get a lock timeout, in which case we retry the operation in the parent transaction. We don't retry if the nested transaction runs into a deadlock, which is what happens in Svata's case. I don't think it's possible that the nested transaction runs into a deadlock with the main transaction, since the main transaction isn't waiting for any locks while the nested transaction is executing, but it may perhaps happen if there are more threads involved?
Anyway, I just wanted to throw out the idea. The patch has not been tested.
> Deadlocks accessing DB metadata
> -------------------------------
>
> Key: DERBY-3693
> URL: https://issues.apache.org/jira/browse/DERBY-3693
> Project: Derby
> Issue Type: Bug
> Components: JDBC
> Affects Versions: 10.3.2.1, 10.3.3.0, 10.4.1.3
> Environment: Linux amd64 or Windows 32bit
> Reporter: Svata Dedic
> Attachments: deadlock.diff
>
>
> My code changes DB structure (create a column), then immediately after setting autocommit back to true, the code rescans the DB metadata
> DatabaseMetaData.getColumns(catalog, schemaName, tableName, null);
> I am sometimes getting a deadlock with these operations:
> 2008-04-16 19:50:47.833 GMT Thread[Default RequestProcessor,1,system] (XID = 569844), (SESSIONID = 2), (DATABASE = /..../a3/.config/localdb/db), (DRDAID = null), Cleanup action starting 2008-04-16 19:50:47.833 GMT Thread[Default RequestProcessor,1,system] (XID = 569844), (SESSIONID = 2), (DATABASE = /..../IJCProjects/a3/.config/localdb/db), (DRDAID = null), Failed Statement is: EXECUTE STATEMENT SYS."getColumns" ERROR 40XL2: A lock could not be obtained within the time requested.
> The lockTable dump is:
> 2008-04-16 19:50:47.796 GMT
> XID |TYPE |MODE|LOCKCOUNT|LOCKNAME |STATE|TABLETYPE /LOCKOBJ |INDEXNAME / CONTAINER_ID / MODE for LATCH only) |TABLENAME / CONGLOM_ID |
> ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> *** The following row is the victim ***
> 569852 |ROW |X |0 |(44,7) |WAIT |S |NULL |SYSSTATEMENTS |
> *** The above row is the victim ***
> The stacktrace of the operation causing the deadlock is
> at org.apache.derby.iapi.error.StandardException.newException(Unknown Source)
> at org.apache.derby.impl.services.locks.Timeout.createException(Unknown Source)
> at org.apache.derby.impl.services.locks.Timeout.buildException(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.RowLocking3.lockRecordForWrite(Unknown Source)
> at org.apache.derby.impl.store.access.heap.HeapController.lockRow(Unknown Source)
> at org.apache.derby.impl.store.access.heap.HeapController.lockRow(Unknown Source)
> at org.apache.derby.impl.store.access.btree.index.B2IRowLocking3.lockRowOnPage(Unknown Source)
> at org.apache.derby.impl.store.access.btree.index.B2IRowLocking3._lockScanRow(Unknown Source)
> at org.apache.derby.impl.store.access.btree.index.B2IRowLockingRR.lockScanRow(Unknown Source)
> at org.apache.derby.impl.store.access.btree.BTreeForwardScan.fetchRows(Unknown Source)
> at org.apache.derby.impl.store.access.btree.BTreeScan.fetchNext(Unknown Source)
> at org.apache.derby.impl.sql.catalog.TabInfoImpl.updateRow(Unknown Source)
> at org.apache.derby.impl.sql.catalog.TabInfoImpl.updateRow(Unknown Source)
> at org.apache.derby.impl.sql.catalog.DataDictionaryImpl.updateSPS(Unknown Source )
> at org.apache.derby.iapi.sql.dictionary.SPSDescriptor.updateSYSSTATEMENTS(Unknown Source)
> at org.apache.derby.iapi.sql.dictionary.SPSDescriptor.getPreparedStatement(Unknown Source)
> at org.apache.derby.iapi.sql.dictionary.SPSDescriptor.getPreparedStatement(Unknown Source)
> at org.apache.derby.impl.sql.compile.ExecSPSNode.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)
> at org.apache.derby.impl.sql.GenericPreparedStatement.execute(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 org.apache.derby.impl.jdbc.EmbedDatabaseMetaData.doGetCols(Unknown Source)
> at org.apache.derby.impl.jdbc.EmbedDatabaseMetaData.getColumns(Unknown Source)
> I've seen the deadlock occur during several get-metadata operations (getImportedKeys, ...), each time waiting on the SYSSTATEMENTS apparently because of internally constructed PreparedStatement. The lock eventually times out and the locked out operation completes without error.
> When the deadlock occurs, the "real" SQL into systables is being compiled (I traced this sql to be the value of "getColumns" key in org/apache/derby/impl/jdbc/metadata.properties file):
> ---------%<-----------------------%<--------------
> Begin compiling prepared statement: SELECT CAST ('' AS VARCHAR(128)) AS PKTABLE_CAT, S.SCHEMANAME AS PKTABLE_SCHEM, TABLENAME AS
> PKTABLE_NAME, COLS.COLUMNNAME AS PKCOLUMN_NAME, CAST ('' AS VARCHAR(128)) AS FKTABLE_CAT, FKTABLE_SCHEM, FKTABLE_NAME, FKCOLUMN_NAME, CAST ...
> ---------%<-----------------------%<--------------
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