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https://issues.apache.org/jira/browse/DERBY-2990?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12544492
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Øystein Grøvlen commented on DERBY-2990:
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The reason ResultSet.getBlob() causes a lock to be held, is to make
sure that the Blob object is stable. (Ref. discussion in DERBY-2892).
In other words, the decribed behavior is intended.
If this JIRA is to be fixed, we will have to implement another mechanism
than locking to guarantee stability of LOB objects.
> ResultSet.getBlob holds locks even with READ_UNCOMMITTED isolation level
> ------------------------------------------------------------------------
>
> Key: DERBY-2990
> URL: https://issues.apache.org/jira/browse/DERBY-2990
> Project: Derby
> Issue Type: Bug
> Components: JDBC
> Affects Versions: 10.1.3.1, 10.2.2.0, 10.3.1.4, 10.4.0.0
> Reporter: Kathey Marsden
> Attachments: GetBlobLocks.java
>
>
> ResultSet.getBlob() holds locks even when isolation level is set to
> TRANSACTION_READ_UNCOMMITTED. See attached repro
> java GetBlobLocks
> Exception in thread "main" 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.LockSet.lockObject(Unknown
> Source)
> at
> org.apache.derby.impl.services.locks.SinglePool.lockAnObject(Unknown Source)
> at org.apache.derby.impl.services.locks.SinglePool.lockObject(Unknown
> Source)
> at
> org.apache.derby.impl.store.raw.xact.RowLocking3.lockRecordForWrite(Unknown
> Source)
> at
> org.apache.derby.impl.store.access.conglomerate.OpenConglomerate.lockPositionForWrite(Unknown
> Source)
> at
> org.apache.derby.impl.store.access.conglomerate.GenericConglomerateController.delete(Unknown
> Source)
> at org.apache.derby.impl.sql.execute.RowChangerImpl.deleteRow(Unknown
> Source)
> at
> org.apache.derby.impl.sql.execute.DeleteResultSet.collectAffectedRows(Unknown
> Source)
> at org.apache.derby.impl.sql.execute.DeleteResultSet.open(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.EmbedStatement.execute(Unknown Source)
> at org.apache.derby.impl.jdbc.EmbedStatement.executeUpdate(Unknown
> Source)
> at GetBlobLocks.testBlobLocks(GetBlobLocks.java:46)
> at GetBlobLocks.main(GetBlobLocks.java:11)
> [C:/kmarsden/repro/getblob] echo $WS
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