[DERBY-3693] Deadlocks accessing DB metadata

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 10.3.2.1, 10.3.3.0, 10.4.1.3
• Fix Version/s: 10.4.2.0, 10.5.1.1
• Component/s: JDBC
• Environment: Linux amd64 or Windows 32bit
• Assignee: Knut Anders Hatlen
• Reporter: Svata Dedic
• Created: 27/May/08 20:55
• Updated: 21/Jan/11 17:51
• Resolved: 25/Aug/08 16:09

Description

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 ...
--------%<---------------------%<-------------

Issue Links

• is duplicated by: DERBY-177 Unnecessary waiting within EmbedDatabaseMetaData.getIndexInfo()
• is related to: DERBY-177 Unnecessary waiting within EmbedDatabaseMetaData.getIndexInfo()
• is related to: DERBY-3850 Remove unneeded workarounds for DERBY-177 and DERBY-3693