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From "Shai Erera (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2316) Define clear semantics for Directory.fileLength
Date Mon, 12 Apr 2010 07:29:42 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2316?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12855873#action_12855873
] 

Shai Erera commented on LUCENE-2316:
------------------------------------

Well ... dir.fileLength is also used by SegmentInfos.sizeInBytes to compute the size of all
the files in the Directory. If we remove fileLength, then SI will need to call dir.openInput.length()
and the close it? Seems like a lot of work to me, for just obtaining the length of the file.
So I agree that if you have an IndexInput at hand, you should call its length() method rather
than Dir.fileLength. But otherwise, if you just have a name at hand, a dir.fileLength is convenient?

I'm also ok w/ the bw break rather than going through the new/deprecate cycle.

> Define clear semantics for Directory.fileLength
> -----------------------------------------------
>
>                 Key: LUCENE-2316
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2316
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>            Reporter: Shai Erera
>            Priority: Minor
>             Fix For: 3.1
>
>
> On this thread: http://mail-archives.apache.org/mod_mbox/lucene-java-dev/201003.mbox/%3C126142c1003121525v24499625u1589bbef4c0792e7@mail.gmail.com%3E
it was mentioned that Directory's fileLength behavior is not consistent between Directory
implementations if the given file name does not exist. FSDirectory returns a 0 length while
RAMDirectory throws FNFE.
> The problem is that the semantics of fileLength() are not defined. As proposed in the
thread, we'll define the following semantics:
> * Returns the length of the file denoted by <code>name</code> if the file
exists. The return value may be anything between 0 and Long.MAX_VALUE.
> * Throws FileNotFoundException if the file does not exist. Note that you can call dir.fileExists(name)
if you are not sure whether the file exists or not.
> For backwards we'll create a new method w/ clear semantics. Something like:
> {code}
> /**
>  * @deprecated the method will become abstract when #fileLength(name) has been removed.
>  */
> public long getFileLength(String name) throws IOException {
>   long len = fileLength(name);
>   if (len == 0 && !fileExists(name)) {
>     throw new FileNotFoundException(name);
>   }
>   return len;
> }
> {code}
> The first line just calls the current impl. If it throws exception for a non-existing
file, we're ok. The second line verifies whether a 0 length is for an existing file or not
and throws an exception appropriately.

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