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  1. Core Server
  2. SERVER-21887

$sample takes disproportionately long time on newly created collection

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      1. Download the attached repro.js
      2. Run test with wiredTiger storage engine ($sample takes about 5200 milliseconds for me) 

        python buildscripts/resmoke.py repro.js

      3. For a baseline of some sort, compare to timing on mmapv1 (about 550 milliseconds) 

        python buildscripts/resmoke.py --storageEngine=mmapv1 repro.js

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      Download the attached repro.js Run test with wiredTiger storage engine ($sample takes about 5200 milliseconds for me) python buildscripts/resmoke.py repro.js For a baseline of some sort, compare to timing on mmapv1 (about 550 milliseconds) python buildscripts/resmoke.py --storageEngine=mmapv1 repro.js

    Description

      Even though SERVER-19182 and SERVER-19183 exist, I have a collection of one million documents on which $sample takes very long time. This shows even on collections with only 10K documents.

      This only happens to collection that was just created. Restarting mongod process "fixes" this symptom.

      Attachments

        1. metrics.2015-12-14T16-20-52Z-00000
          117 kB
        2. perf-sample.png
          perf-sample.png
          121 kB
        3. repro.js
          0.4 kB
        4. Screenshot 2015-12-14 10.07.31.png
          Screenshot 2015-12-14 10.07.31.png
          399 kB

        Issue Links

          is duplicated by

          Improvement - An improvement or enhancement to an existing feature or task. SERVER-24710 Optimize $sample+$project

          • Minor - P4 - Minor loss of function, or other problem where easy workaround is present.
          • Closed
          is related to

          Bug - A problem which impairs or prevents the functions of the product. SERVER-23661 $sample takes disproportionately long time on newly created collection

          • Major - P3 - Major loss of function.
          • Closed
          related to

          Bug - A problem which impairs or prevents the functions of the product. WT-2291 Random cursor walk inefficient in skip list only trees

          • Major - P3 - Major loss of function.
          • Closed
          links to

          Web Link https://github.com/wiredtiger/wiredtiger/pull/2394

          Activity

            People

              keith.bostic@mongodb.com Keith Bostic (Inactive)
              asya.kamsky@mongodb.com Asya Kamsky
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              Dates

                Created:
                Updated:
                Resolved: