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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (DERBY-6075) Use modern collections in impl/sql/compile
Date Thu, 07 Mar 2013 10:14:17 GMT

     [ https://issues.apache.org/jira/browse/DERBY-6075?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Knut Anders Hatlen updated DERBY-6075:
--------------------------------------

    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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