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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-3693) Deadlocks accessing DB metadata
Date Tue, 19 Aug 2008 14:21:44 GMT

    [ https://issues.apache.org/jira/browse/DERBY-3693?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12623683#action_12623683
] 

Knut Anders Hatlen commented on DERBY-3693:
-------------------------------------------

I ran suites.All and derbyall successfully with
nested_transaction.diff, but it took very long time for the tests to
complete. I think that the problem is that the patch attempts to
update SYSSTATEMENTS in a nested transaction every time an SPS is
invalidated, regardless of why the invalidation request was sent. In
some of those cases (like when makeInvalid() is called with action =
DependencyManager.CREATE_TRIGGER) the user transaction already holds
locks on rows in SYSSTATEMENTS and the nested transaction almost
definitely runs into a lock conflict with its parent.

To fix the reported issue without introducing hangs in other cases, we
can probably limit the use of nested transactions to the case where
makeInvalid() is called for recompile requests
(INTERNAL_RECOMPILE_REQUEST and possibly USER_RECOMPILE_REQUEST)

> 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
>            Assignee: Knut Anders Hatlen
>         Attachments: d3693.java, deadlock.diff, derby.log, GetTables.java, nested_transaction.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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