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