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https://issues.apache.org/jira/browse/DERBY-6075?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Knut Anders Hatlen updated DERBY-6075:
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Attachment: d6075-9a-hashtable-fields.diff
Attaching d6075-9a-hashtable-fields.diff which removes the last three
Hashtables in the package. They are all used as sets, so they're
replaced with HashSets rather than HashMaps.
None of them require synchronization, as they are not shared between
threads, so using HashSets should be safe. Details:
- DMLModStatementNode.graphHashTable is created and used during the
single-threaded bind phase only (used to track FK dependencies for
cascading deletes)
- Predicate.searchClauseHT is only used during query preprocessing to
calculate the transitive closure for WHERE clauses
- VTIDeferModPolicy.columns lives only for the duration of a call to
the deferIt() method, during which it does not escape to other
threads
All regression tests ran cleanly with the patch.
> Use modern collections in impl/sql/compile
> ------------------------------------------
>
> Key: DERBY-6075
> URL: https://issues.apache.org/jira/browse/DERBY-6075
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.10.0.0
> Reporter: Knut Anders Hatlen
> Assignee: Knut Anders Hatlen
> Priority: Minor
> Attachments: d6075-1a-CollectNodesVisitor.diff,
> d6075-2a-bindExpression.diff, d6075-3a-javadoc.diff,
> d6075-4a-parameterList.diff, d6075-5a-ordering.diff,
> d6075-6a-DMLModStatementNode.diff, d6075-7a-more-signatures.diff,
> d6075-8a-local-hashtables.diff, d6075-9a-hashtable-fields.diff
>
>
> The code in the org.apache.derby.impl.sql.compile package predates the Java
> Collections Framework and uses old-style collections like java.util.Vector
> and java.util.Hashtable. Since the old-style collection classes are used in
> many method signatures, it's difficult to use modern collection classes when
> adding new code.
> I suggest we switch to using interfaces (like java.util.List and
> java.util.Map) instead of specific classes in the signatures, so that we have
> more flexibility in choosing the right collection class for the job.
> Only changing the signatures would allow us to continue using Vector and
> Hashtable, since they implement the interfaces. However, I think it would be
> good to switch to ArrayList and HashMap in a second step. The instances in
> impl/sql/compile are not shared between threads, so we don't need the
> synchronization provided by the old-style classes. Switching to
> unsynchronized classes may make compilation slightly faster.
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