[jira] Commented: (AVRO-757) Allow a DataFile to be reopened without reading the head

["Doug Cutting (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/AVRO-757?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12990680#comment-12990680 ] 

Doug Cutting commented on AVRO-757:
-----------------------------------

This sounds reasonable.

The specification includes a schema that corresponds to the file header.

http://avro.apache.org/docs/current/spec.html#Object+Container+Files

Perhaps we should implement this by adding the following methods to DataFileReader:
 - public Header getHeader();
 - public static FileReader<D> openReader(SeekableInput in, DatumReader<D>, Header);

The openReader() implementation should probably call sync(in.tell()), although there might be cases where you want it to instead just call seek(in.tell()).  Perhaps there should be a boolean 'sync' parameter to that method that defaults to true?

> Allow a DataFile to be reopened without reading the head
> --------------------------------------------------------
>
>                 Key: AVRO-757
>                 URL: https://issues.apache.org/jira/browse/AVRO-757
>             Project: Avro
>          Issue Type: New Feature
>          Components: java
>            Reporter: Stu Hood
>            Assignee: Stu Hood
>              Labels: file
>             Fix For: 1.5.0
>
>
> It is useful to be able to re-open a file without needing to seek to the head of the stream to collect metadata and schema that you've read before.

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