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  1. Kudu
  2. KUDU-2463

Different results returned by group by on count() metric

    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Critical
    • Resolution: Fixed
    • Affects Version/s: 1.5.0
    • Fix Version/s: 1.8.0
    • Component/s: impala
    • Labels:
      None

      Description

      Hi, 

      I have a static table in Kudu, no inserts/updates or deletes are running on the cluster. The query returns DIFFERENT result when I change the where condition on one of the primary key columns, which is in the group_by list.

      The created_date is part of the PK and is type of int.

      PK contains subscriber, time, date, identifier and created_date.

      I tried to check if the inserted count is equal to the HDFS table, and noticed on one day, that the count differs based on the where criteria!!

       

      [10.197.0.164:21000] > select created_date, count from base.usage_kudu where created_date >= 20180601 group by created_date;
      Query: select created_date, count from base.usage_kudu where created_date >= 20180601 group by created_date
      Query submitted at: 2018-06-04 21:06:30 (Coordinator: http://ip-10-197-0-164.eu-west-1.compute.internal:25000)
      Query progress can be monitored at: http://ip-10-197-0-164.eu-west-1.compute.internal:25000/query_plan?query_id=ce4e92eda5aaa02f:ea07aa4600000000
      ----------------------+
      | created_date | count |
      ----------------------+
      | 20180603 | 12145131 |
      | 20180601 | 18076448 | -> 195k MORE!!!
      | 20180602 | 13325080 |
      | 20180604 | 3788161 |
      ----------------------+
      Fetched 4 row(s) in 0.37s
      [10.197.0.164:21000] >
      [10.197.0.164:21000] >
      [10.197.0.164:21000] > select created_date, count from base.usage_kudu where created_date >= 20180601 group by created_date order by 1;
      Query: select created_date, count from base.usage_kudu where created_date >= 20180601 group by created_date order by 1
      Query submitted at: 2018-06-04 21:06:55 (Coordinator: http://ip-10-197-0-164.eu-west-1.compute.internal:25000)
      Query progress can be monitored at: http://ip-10-197-0-164.eu-west-1.compute.internal:25000/query_plan?query_id=d541a9dda19e28e4:be4a2ca000000000
      ----------------------+
      | created_date | count |
      ----------------------+
      | 20180601 | 18076448 | -> 195k MORE!!!
      | 20180602 | 13325080 |
      | 20180603 | 12145131 |
      | 20180604 | 3788161 |
      ----------------------+
      Fetched 4 row(s) in 1.14s
      [10.197.0.164:21000] > select created_date, count from base.usage_kudu where created_date >= 20180528 group by created_date order by 1;
      Query: select created_date, count from base.usage_kudu where created_date >= 20180528 group by created_date order by 1
      Query submitted at: 2018-06-04 21:07:12 (Coordinator: http://ip-10-197-0-164.eu-west-1.compute.internal:25000)
      Query progress can be monitored at: http://ip-10-197-0-164.eu-west-1.compute.internal:25000/query_plan?query_id=774a261fb94ad2bb:aab28b8b00000000
      ----------------------+
      | created_date | count |
      ----------------------+
      | 20180528 | 17607943 |
      | 20180529 | 20741097 |
      | 20180530 | 17362364 |
      | 20180531 | 16877228 |
      {{| 20180601 | 17925671 | -> 44k MORE!! }}
      | 20180602 | 13325080 |
      | 20180603 | 12145131 |
      | 20180604 | 3788161 |
      ----------------------+
      Fetched 8 row(s) in 0.67s
      [10.197.0.164:21000] > select created_date, count from base.usage_kudu where created_date >= 20180525 group by created_date order by 1;
      Query: select created_date, count from base.usage_kudu where created_date >= 20180525 group by created_date order by 1
      Query submitted at: 2018-06-04 21:07:25 (Coordinator: http://ip-10-197-0-164.eu-west-1.compute.internal:25000)
      Query progress can be monitored at: http://ip-10-197-0-164.eu-west-1.compute.internal:25000/query_plan?query_id=38483ad3ae5c8eb9:a538cb6300000000
      ----------------------+
      | created_date | count |
      ----------------------+
      | 20180525 | 22309857 |
      | 20180526 | 15268520 |
      | 20180527 | 14939691 |
      | 20180528 | 17607943 |
      | 20180529 | 20741097 |
      | 20180530 | 17362364 |
      | 20180531 | 16903829 |
      | 20180601 | 18047010 | -> 165k MORE!!!
      | 20180602 | 13325080 |
      | 20180603 | 12145131 |
      | 20180604 | 3788161 |
      ----------------------+
      Fetched 11 row(s) in 0.85s
      [10.197.0.164:21000] > select created_date, count from base.usage_kudu where created_date = 20180601 group by created_date;
      Query: select created_date, count from base.usage_kudu where created_date = 20180601 group by created_date
      Query submitted at: 2018-06-04 21:07:42 (Coordinator: http://ip-10-197-0-164.eu-west-1.compute.internal:25000)
      Query progress can be monitored at: http://ip-10-197-0-164.eu-west-1.compute.internal:25000/query_plan?query_id=7343ba31f6b4c86f:621a7b8c00000000
      ----------------------+
      | created_date | count |
      ----------------------+
      | 20180601 | 17881253 | -> CORRECT ONE
      ----------------------+
      Fetched 1 row(s) in 0.27s
      [10.197.0.164:21000] > select created_date, count from base.usage_kudu where created_date >= 20180525 group by created_date order by 1;
      Query: select created_date, count from base.usage_kudu where created_date >= 20180525 group by created_date order by 1
      Query submitted at: 2018-06-04 21:12:02 (Coordinator: http://ip-10-197-0-164.eu-west-1.compute.internal:25000)
      Query progress can be monitored at: http://ip-10-197-0-164.eu-west-1.compute.internal:25000/query_plan?query_id=4141df26117f35c3:9ab2f0700000000
      ----------------------+
      | created_date | count |
      ----------------------+
      | 20180525 | 22309857 |
      | 20180526 | 15268520 |
      | 20180527 | 14939691 |
      | 20180528 | 17607943 |
      | 20180529 | 20741097 |
      | 20180530 | 17362364 |
      | 20180531 | 16903829 |
      | 20180601 | 18047010 | -> AGAIN WRONG RESULT!!
      | 20180602 | 13325080 |
      | 20180603 | 12145131 |
      | 20180604 | 3788161 |
      ----------------------+
      Fetched 11 row(s) in 1.04s}}{{

      Again, no other inserts/selects/updates or deletes were running between these statements on the cluster. 

       

      I checked the explain, if there is a difference,but it looks ok. But the result is different!

       

      [10.197.0.164:21000] > explain select created_date, count from base.usage_kudu where created_date = 20180601 group by created_date;
      Query: explain select created_date, count from base.usage_kudu where created_date = 20180601 group by created_date
      --------------------------------------------------
      | Explain String |
      --------------------------------------------------
      | Max Per-Host Resource Reservation: Memory=3.94MB |
      | Per-Host Resource Estimates: Memory=20.00MB |
      | |
      | PLAN-ROOT SINK |
      | | |
      | 04:EXCHANGE [UNPARTITIONED] |
      | | |
      | 03:AGGREGATE [FINALIZE] |
      | | output: count:merge |
      | | group by: created_date |
      | | |
      | 02:EXCHANGE [HASH(created_date)] |
      | | |
      | 01:AGGREGATE [STREAMING] |
      | | output: count |
      | | group by: created_date |
      | | |
      | 00:SCAN KUDU [base.usage_kudu] |
      | kudu predicates: created_date = 20180601 |
      --------------------------------------------------
      Fetched 19 row(s) in 0.06s
      [10.197.0.164:21000] > select created_date, count from base.usage_kudu where created_date = 20180601 group by created_date;
      Query: select created_date, count from base.usage_kudu where created_date = 20180601 group by created_date
      Query submitted at: 2018-06-04 21:17:21 (Coordinator: http://ip-10-197-0-164.eu-west-1.compute.internal:25000)
      Query progress can be monitored at: http://ip-10-197-0-164.eu-west-1.compute.internal:25000/query_plan?query_id=c449aabea51e7456:612f096400000000
      ----------------------+
      | created_date | count |
      ----------------------+
      | 20180601 | 17881253 |
      ----------------------+
      Fetched 1 row(s) in 0.38s
      [10.197.0.164:21000] > explain select created_date, count from base.usage_kudu where created_date >= 20180525 group by created_date order by 1;
      Query: explain select created_date, count from base.usage_kudu where created_date >= 20180525 group by created_date order by 1
      --------------------------------------------------
      | Explain String |
      --------------------------------------------------
      | Max Per-Host Resource Reservation: Memory=9.94MB |
      | Per-Host Resource Estimates: Memory=26.00MB |
      | |
      | PLAN-ROOT SINK |
      | | |
      | 05:MERGING-EXCHANGE [UNPARTITIONED] |
      | | order by: created_date ASC |
      | | |
      | 02:SORT |
      | | order by: created_date ASC |
      | | |
      | 04:AGGREGATE [FINALIZE] |
      | | output: count:merge |
      | | group by: created_date |
      | | |
      | 03:EXCHANGE [HASH(created_date)] |
      | | |
      | 01:AGGREGATE [STREAMING] |
      | | output: count |
      | | group by: created_date |
      | | |
      | 00:SCAN KUDU [base.usage_kudu] |
      | kudu predicates: created_date >= 20180525 |
      --------------------------------------------------
      Fetched 23 row(s) in 0.05s
      [10.197.0.164:21000] > select created_date, count from base.usage_kudu where created_date >= 20180525 group by created_date order by 1;
      Query: select created_date, count from base.usage_kudu where created_date >= 20180525 group by created_date order by 1
      Query submitted at: 2018-06-04 21:17:32 (Coordinator: http://ip-10-197-0-164.eu-west-1.compute.internal:25000)
      Query progress can be monitored at: http://ip-10-197-0-164.eu-west-1.compute.internal:25000/query_plan?query_id=bc4a36f2a7ad3280:c7b09a5100000000
      ----------------------+
      | created_date | count |
      ----------------------+
      | 20180525 | 22309857 |
      | 20180526 | 15268520 |
      | 20180527 | 14939691 |
      | 20180528 | 17607943 |
      | 20180529 | 20741097 |
      | 20180530 | 17362364 |
      | 20180531 | 16903829 |
      | 20180601 | 18047010 |
      | 20180602 | 13325080 |
      | 20180603 | 12145131 |
      | 20180604 | 3788161 |
      ----------------------+
      Fetched 11 row(s) in 0.88s

       

        Attachments

        1. checksum_scan.txt
          13 kB
          Rodion Myronov
        2. fs_check_master_servers.txt
          5 kB
          Rodion Myronov
        3. fs_check_tablet_servers.txt
          6 kB
          Rodion Myronov

          Activity

            People

            • Assignee:
              andrew.wong Andrew Wong
              Reporter:
              farkastfbic Tomas Farkas
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              Dates

              • Created:
                Updated:
                Resolved: