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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 Mon, 04 Mar 2013 16:05:13 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: d6075-7a-more-signatures.diff

Attaching d6075-7a-more-signatures.diff, which changes the rest of the fields and methods
(that I could find) in the impl/sql/compile package to use List instead of Vector.

Apart from the pure signature changes, the patch changes some occurrences of:

- Vector.copyInto() -> List.toArray()
- Vector.elementAt() -> List.get()
- Vector.addElement() -> List.add()
- Enumerator -> Iterator
- size() == 0 -> isEmpty()

The Enumerator that's changed to an Iterator walks a Vector that's created by the parser and
never modified after it leaves the parser, so switching to Iterator should not create a risk
for ConcurrentModificationExceptions.

The patch does not change any Vector instances to ArrayLists. It changes the signatures only.
                
> 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
>
>
> 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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