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A complete RC support on DB2 & BLU

  • 1.  A complete RC support on DB2 & BLU

    Posted 07/20/20 01:02 PM
    Edited by System Admin 01/20/23 04:21 PM
    Hi,

    "a complete RP support ..."

    RP is not fully supported on DB2, there is no range stats usable by the DB2 optimizer, therefore access plans is based on "Nb rows / Nb partitions used". This gives inaccurate estimations.
    P1 = 1 million
    P2 = 1 million
    P3 = 0.1 million
    select * from tab where part = P3 ==> card estimates: 2,1/3 = 0.7 million.
    Oracle estimation: 0,1 million

    RP is not supported  on DB2 BLU. Compression column dictionary is based on 5 million rows. With a 13 billion row table, the "manual split" using UNION ALL views show that storage savings is 18 % ! a dictionary on smaller tables is better.

    When will we get RP full support ?  This feature seems to me more important that having "automatically created column aliases" on CTE tables using functions.

    Thanks,

    ------------------------------
    Jean-Marc BLAISE
    ------------------------------
    #Db2


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