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https://issues.apache.org/jira/browse/SOLR-912?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12656408#action_12656408
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Kay Kay commented on SOLR-912:
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The interface is mostly used as a proof of concept that the new class -
ModernNamedList implements the same methods as that of NamedList. Eventually -
the interface would be gotten rid of , once we are happy with the same.
As far as NamedList , I believe if we want to have the flexibility of allowing
any type in it - we might as well define it to an Object. If we do qualify it
as a specific type - then we might as well implement type-safety in the class.
javac does not complain today because the compiler switch to indicate
type-safety errors has been turned off.
Previous implementation used to be having a pre-jdk5 List , with members being
String and a type depending on the index. The revised implementation has
Map.Entry<String, T> interface - which is directly intuitive to what is
required ( a Map with order being preserved , allowing duplicates and nulls ).
I did profile with 2 different implementations , involving Map.Entry<?> and a
heterogenous list with String and a type (with insertion / deletion of 100,000
records). The current implementation in fact , failed in the performance
comparison in both insertion / deletion in the middle of the List ( remove () )
, since we have to add/remove elements twice from the List (as in the current
impl) , as compared to 1 insertion/deletion in the Map.Entry<> implementation.
) Given that addition/deletion in the List is worst-case linear - I believe the
perceived performance degradation due to additional object , turns out to be
not so bad when compared to 2-path insertion / deletion as we have today.
NamedList does seem to implement the interface Iterable<T> . I am not sure how
the consumer of the API can have independent iterators (since only NamedList is
supposed to be aware of the internal data structures and not the consumer). So
I believe it would be upto NamedList<T> to provide an iterator to the user of
the API.
> org.apache.solr.common.util.NamedList - Typesafe efficient variant -
> ModernNamedList introduced - implementing the same API as NamedList
> ----------------------------------------------------------------------------------------------------------------------------------------
>
> Key: SOLR-912
> URL: https://issues.apache.org/jira/browse/SOLR-912
> Project: Solr
> Issue Type: Improvement
> Components: clients - java
> Affects Versions: 1.4
> Environment: Tomcat 6, JRE 6, Solr 1.3+ nightlies
> Reporter: Kay Kay
> Priority: Minor
> Fix For: 1.3.1
>
> Attachments: SOLR-912.patch
>
> Original Estimate: 72h
> Remaining Estimate: 72h
>
> The implementation of NamedList - while being fast - is not necessarily
> type-safe. I have implemented an additional implementation of the same -
> ModernNamedList (a type-safe variation providing the same interface as
> NamedList) - while preserving the semantics in terms of ordering of elements
> and allowing null elements for key and values (keys are always Strings ,
> while values correspond to generics ).
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