[jira] [Commented] (HBASE-5110) code enhancement - remove unnecessary if-checks in every loop in HLog class

["Mikael Sitruk (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-5110?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13178192#comment-13178192 ] 

Mikael Sitruk commented on HBASE-5110:
--------------------------------------

I see it a lot in the heavy write scenario when major compaction occurs in the background, but to be realistic even when i see this method called 2000 times during a test of 5 hours, across a cluster of 10 RS (each RS log contains +/-200 calls of this method), i don't think this method present a performance problem.
So for my point of view this is more readability issue before it becomes a performance problem. It is strange to me to see code asking each time in an iteration for object existence especially if creating the object is not heavy task.


                
> code enhancement - remove unnecessary if-checks in every loop in HLog class
> ---------------------------------------------------------------------------
>
>                 Key: HBASE-5110
>                 URL: https://issues.apache.org/jira/browse/HBASE-5110
>             Project: HBase
>          Issue Type: Improvement
>          Components: wal
>    Affects Versions: 0.90.1, 0.90.2, 0.90.4, 0.92.0
>            Reporter: Mikael Sitruk
>            Priority: Minor
>
> The HLog class (method findMemstoresWithEditsEqualOrOlderThan) has unnecessary if check in a loop.
>  static byte [][] findMemstoresWithEditsEqualOrOlderThan(final long oldestWALseqid,
>       final Map<byte [], Long> regionsToSeqids) {
>     //  This method is static so it can be unit tested the easier.
>     List<byte []> regions = null;
>     for (Map.Entry<byte [], Long> e: regionsToSeqids.entrySet()) {
>       if (e.getValue().longValue() <= oldestWALseqid) {
>         if (regions == null) regions = new ArrayList<byte []>();
>         regions.add(e.getKey());
>       }
>     }
>     return regions == null?
>       null: regions.toArray(new byte [][] {HConstants.EMPTY_BYTE_ARRAY});
>   }
> The following change is suggested
>   static byte [][] findMemstoresWithEditsEqualOrOlderThan(final long oldestWALseqid,
>       final Map<byte [], Long> regionsToSeqids) {
>     //  This method is static so it can be unit tested the easier.
>     List<byte []> regions = new ArrayList<byte []>();
>     for (Map.Entry<byte [], Long> e: regionsToSeqids.entrySet()) {
>       if (e.getValue().longValue() <= oldestWALseqid) {
>         regions.add(e.getKey());
>       }
>     }
>     return regions.size() == 0?
>       null: regions.toArray(new byte [][] {HConstants.EMPTY_BYTE_ARRAY});
>   }

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