HADOOP-18395. Performance improvement in hadoop-common Text#find #4714

asdfgh19 · 2022-08-07T07:34:43Z

Description of PR

JIRA: HADOOP-18395
The current implementation reset src and tgt to the mark and continues searching when tgt has remaining and src expired first. which is probably not necessary.
In some cases, this commit can reduce the complexity from O(n²) to O(n), which can significantly improve performance, as in the following example.

  public void testFindWithTimeout() throws Exception {
    byte[] bytes = new byte[1000000];
    Arrays.fill(bytes, (byte) 97);
    String what = new String(bytes);
    bytes[0] = (byte) 98;
    Text text = new Text(bytes);

    assertThat(text.find(what)).isEqualTo(-1);
  }

How was this patch tested?

unit test in org.apache.hadoop.io.TestText#testFind

hadoop-yetus · 2022-08-07T11:24:53Z

🎊 +1 overall

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ZanderXu

@huxinqiu Thanks for your report. LGTM.

Can you add one UT with a very long string and timeout to test the performance of this method?

hadoop-yetus · 2022-08-08T08:36:34Z

🎊 +1 overall

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hadoop-yetus · 2022-12-28T11:10:21Z

💔 -1 overall

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hadoop-yetus · 2023-10-25T06:55:49Z

🎊 +1 overall

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github-actions · 2025-11-06T00:23:21Z

We're closing this stale PR because it has been open for 100 days with no activity. This isn't a judgement on the merit of the PR in any way. It's just a way of keeping the PR queue manageable.
If you feel like this was a mistake, or you would like to continue working on it, please feel free to re-open it and ask for a committer to remove the stale tag and review again.
Thanks all for your contribution.

retrun -1 when tgt has remaining and src expired first in Text.find

86bfbe6

ZanderXu reviewed Aug 7, 2022

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add UT with timeout for Text#find and fix comments

49ae6cd

ZanderXu approved these changes Aug 8, 2022

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asdfgh19 changed the title ~~HADOOP-18395 Performance improvement in org.apache.hadoop.io.Text#find~~ HADOOP-18395. Performance improvement in hadoop-common Text#find Aug 10, 2022

asdfgh19 closed this by deleting the head repository Nov 23, 2022

asdfgh19 reopened this Dec 28, 2022

github-actions bot added the Stale label Nov 6, 2025

github-actions bot closed this Nov 7, 2025

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