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From "Adrien Grand (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-8476) Bug fix and optimizations in UserDictionary(KoreanAnalyzer)
Date Mon, 03 Sep 2018 21:21:00 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-8476?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16602449#comment-16602449
] 

Adrien Grand commented on LUCENE-8476:
--------------------------------------

The problem with calling BufferedReader#close is that it will also close the underlying stream,
which is unexpected? Other points make sense to me.

>  Bug fix and optimizations in UserDictionary(KoreanAnalyzer)
> ------------------------------------------------------------
>
>                 Key: LUCENE-8476
>                 URL: https://issues.apache.org/jira/browse/LUCENE-8476
>             Project: Lucene - Core
>          Issue Type: Bug
>          Components: modules/analysis
>            Reporter: Namgyu Kim
>            Priority: Major
>              Labels: bugfix, memory-leak, optimization, patch-available
>         Attachments: LUCENE-8476.patch
>
>
> ■ Bug fix
> 1) BufferedReader's close method is not called.
> {code:java}
> // Line 57 method
> public static UserDictionary open(Reader reader) throws IOException {
>   BufferedReader br = new BufferedReader(reader);
>   String line = null;
>   List<String> entries = new ArrayList<>();
>   // text + optional segmentations
>   while ((line = br.readLine()) != null) {
>     ...
>   }
>   if (entries.isEmpty()) {
>     return null;
>   } else {
>     return new UserDictionary(entries);
>   }
> }{code}
> If you look at the code above, there is no close() method for the "br" variable.
>  As I know, BufferedReader can cause a +memory leak+ if the close method is not called.
>  So I changed the code below.
> {code:java}
> // Line 57 method
> public static UserDictionary open(Reader reader) throws IOException {
>   String line = null;
>   List<String> entries = new ArrayList<>();
>   // text + optional segmentations
>   try (BufferedReader br = new BufferedReader(reader)) {
>     while ((line = br.readLine()) != null) {
>       ...
>     }
>   }
>   if (entries.isEmpty()) {
>     return null;
>   } else {
>     return new UserDictionary(entries);
>   }
> }
> {code}
> I solved this problem with "[try-with-resources|https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html]"
method available since Java 7.
>  
> ■ Optimizations
> 1) Change from Collections.sort to List.sort (UserDictionary constructor)
> {code:java}
> // Line 82 method
> private UserDictionary(List<String> entries) throws IOException {
>   final CharacterDefinition charDef = CharacterDefinition.getInstance();
>   Collections.sort(entries,
>       Comparator.comparing(e -> e.split("\\s+")[0]));
>   PositiveIntOutputs fstOutput = PositiveIntOutputs.getSingleton();
>   ...
> }{code}
> List.sort in Java 8 is known to be faster than existing Collections.sort. ([http://ankitsambyal.blogspot.com/2014/03/difference-between-listsort-and.html])
So I changed the code below.
> {code:java}
> // Line 82 method
> private UserDictionary(List<String> entries) throws IOException {
>   final CharacterDefinition charDef = CharacterDefinition.getInstance();
>   entries.sort(Comparator.comparing(e -> e.split("\\s+")[0]));
>   PositiveIntOutputs fstOutput = PositiveIntOutputs.getSingleton();
>   ...
> }{code}
>  
> 2) Remove unnecessary null check (UserDictionary constructor)
> {code:java}
> // Line 82 method
> private UserDictionary(List<String> entries) throws IOException {
>   ...
>   String lastToken = null;
>   ...
>   for (String entry : entries) {
>     String[] splits = entry.split("\\s+");
>     String token = splits[0];
>     if (lastToken != null && token.equals(lastToken)) {
>       continue;
>     }
>     char lastChar = entry.charAt(entry.length()-1);
>   ...
> }{code}
> Looking at this part of the code,
> {code:java}
> if (lastToken != null && token.equals(lastToken)) {
>   continue;
> }{code}
> A null check for lastToken is unnecessary.
>  Because the equals method of the String class internally performs a null check.
>  So I changed the code as below.
> {code:java}
> // Line 82 method
> private UserDictionary(List<String> entries) throws IOException {
>   ...
>   String lastToken = null;
>   ...
>   for (String entry : entries) {
>     String[] splits = entry.split("\\s+");
>     String token = splits[0];
>     if (token.equals(lastToken)) {
>       continue;
>     }
>     char lastChar = entry.charAt(entry.length()-1);
>   ...
> }{code}



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