[jira] [Commented] (FLINK-6776) Use skip instead of seek for small forward repositioning in DFS streams

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-6776?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16047644#comment-16047644 ] 

ASF GitHub Bot commented on FLINK-6776:
---------------------------------------

Github user tillrohrmann commented on a diff in the pull request:

    https://github.com/apache/flink/pull/4019#discussion_r121627730
  
    --- Diff: flink-runtime/src/main/java/org/apache/flink/runtime/fs/hdfs/HadoopDataInputStream.java ---
    @@ -89,4 +99,14 @@ public long skip(long n) throws IOException {
     	public org.apache.hadoop.fs.FSDataInputStream getHadoopInputStream() {
     		return fsDataInputStream;
     	}
    +
    +	public void forceSeek(long seekPos) throws IOException {
    +		fsDataInputStream.seek(seekPos);
    +	}
    +
    +	public void skipFully(long bytes) throws IOException {
    --- End diff --
    
    JavaDocs


> Use skip instead of seek for small forward repositioning in DFS streams
> -----------------------------------------------------------------------
>
>                 Key: FLINK-6776
>                 URL: https://issues.apache.org/jira/browse/FLINK-6776
>             Project: Flink
>          Issue Type: Improvement
>          Components: State Backends, Checkpointing
>            Reporter: Stefan Richter
>            Assignee: Stefan Richter
>            Priority: Minor
>
> Reading checkpoint meta data and finding key-groups in restores sometimes require to seek in input streams. Currently, we always use a seek, even for small position changes. As small true seeks are far more expensive than small reads/skips, we should just skip over small gaps instead of performing the seek.



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