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  1. MariaDB ColumnStore
  2. MCOL-403

Huge cost of ExtendMap on time distribution and filtering per attribute on small range

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    • Task
    • Status: Closed (View Workflow)
    • Major
    • Resolution: Won't Do
    • None
    • Icebox
    • N/A
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    Description

      When data distribution is loaded per datetime

      --------------------------------------+

      count(distinct id) count

      --------------------------------------+

      46347 6153751125

      --------------------------------------+

      select count from fulldata where id=12675;
      ----------

      count

      ----------

      442005

      ----------
      1 row in set (4.06 sec)

      MaxMemPct-0;
      NumTempFiles-0;
      TempFileSpace-0B;
      ApproxPhyI/O-0;
      CacheI/O-3005367;
      BlocksTouched-3005367;
      PartitionBlocksEliminated-0;
      MsgBytesIn-88MB;
      MsgBytesOut-704KB;

      Desc Mode Table TableOID ReferencedColumns PIO LIO PBE Elapsed Rows
      BPS PM fulldata 3108 (idProducer) 0 3005367 0 4.008 751344
      TAS UM - - - - - - 4.007 1

      When data is loaded per id
      select count from fulldataOrdered where id=12675;
      ----------

      count

      ----------

      442005

      ----------
      1 row in set (0.07 sec)

      MariaDB [datagenerated]> select calgetstats();

      MaxMemPct-0;
      NumTempFiles-0;
      TempFileSpace-0B;
      ApproxPhyI/O-0;
      CacheI/O-16384;
      BlocksTouched-16384;
      PartitionBlocksEliminated-563697;
      MsgBytesIn-492KB;
      MsgBytesOut-6KB;
      Mode-Distributed

      Partition elimination does not work in the first distribution

      Desc Mode Table TableOID ReferencedColumns PIO LIO PBE Elapsed Rows
      BPS PM fulldataordered 3216 (idProducer) 0 16384 582408 0.078 4096
      TAS UM - - - - - - 0.076 1

      When comparing both results there is a huge diff
      MsgBytesIn 88MB and 751344 Rows sent
      492KB MsgBytesIn and 4096 Rows sent
      It looks that or the condition is not push down or the full block is send to UM and row extract taking place in UM ?

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            Unassigned Unassigned
            stephane@skysql.com VAROQUI Stephane
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            Dates

              Created:
              Updated:
              Resolved:

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