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https://issues.apache.org/jira/browse/DERBY-3693?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12614889#action_12614889
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Knut Anders Hatlen commented on DERBY-3693:
-------------------------------------------
It seems like the plan for the meta-data query is invalidated in the user
transaction. When the plan is invalidated, SYS.SYSSTATEMENTS is updated to
reflect that the plan is invalid, hence the user transaction has an exclusive
lock on a row in SYS.SYSSTATEMENTS. However, the meta-data query is recompiled
in a sub-transaction, and therefore it runs into a lock conflict with the user
transaction. Perhaps we could get around this problem by also performing the
invalidation in a sub-transaction so that the exclusive lock is released once
the plan has been marked as invalid. Statements within triggers probably also
suffer from the same problem.
> 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: d3693.java, deadlock.diff, derby.log, GetTables.java
>
>
> 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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