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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 Tue, 12 Mar 2013 13:41:13 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: d6075-13a-unused-properties.diff

Another kind of synchronized collection used in impl/sql/compile is Properties (extends Hashtable).
Those instances are also used by other packages, like in the store, so I'm not planning to
change them to Maps as part of this issue.

Just one small cleanup patch related to Properties: d6075-13a-unused-properties.diff removes
import statements for java.util.Properties in classes where Properties is not used. I also
found that calls from CompilerContextImpl to TransactionController.openSortCostController()
passed a Properties argument that was always null. Since openSortCostController() in fact
ignores that parameter, I removed it from the method signature.

All 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: d6075-10a-aggregate-vectors.diff, d6075-11a-remaining-vectors.diff,
d6075-12a-stack.diff, d6075-13a-unused-properties.diff, 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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