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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 Fri, 22 Mar 2013 14:47:15 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: Compile.java

Dag asked if there was any measurable performance improvement, so I ran a quick and completely
unscientific experiment with the attached Compile.java class.

The class repeatedly compiles the following statement:

    select max(x) from (values 1,2,3) v(x)

(Why did I choose exactly this statement? Firstly, it doesn't touch any physical tables, so
it shouldn't need to involve store or dictionary when compiling. Secondly, it calls an aggregate
function, so I presume it will use the data structure previously known as aggregateVector,
and we get to exercise at least some of the new code.)

The statement cache is disabled, so that the statement is actually compiled each time prepareStatement()
is called.

Running the test several times to filter out variance/noise, I seem to be getting about 15-20%
better results with 10.10.1.1 than with 10.9.1.0. (Test environment: Java 7, Solaris 11.)

Now, there are many other changes between 10.9.1.0 and 10.10.1.1, so there's no evidence that
changing the collections improved compilation speed measurably. But at the very least it looks
like we're heading in the right direction. :)
                
> 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: 10.10.1.1
>            Reporter: Knut Anders Hatlen
>            Assignee: Knut Anders Hatlen
>            Priority: Minor
>         Attachments: Compile.java, d6075-10a-aggregate-vectors.diff, d6075-11a-remaining-vectors.diff,
d6075-12a-stack.diff, d6075-13a-unused-properties.diff, d6075-14a-dead-syntax.diff, d6075-15a-sqlgrammar-vectors.diff,
d6075-16a-negative-test.diff, d6075-17a-rename-aggregate-vectors.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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