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Column UDFs - IBM DB2

NOT DETERMINSTIC will also do. W.r.t. user defined aggregates you can use a scratchpad UDF to simulate this. You aggregate in the scratchpad and then collapse using a MAX(). Cheers Serge...

  1. #1

    Default Re: Column UDFs

    NOT DETERMINSTIC will also do.

    W.r.t. user defined aggregates you can use a scratchpad UDF to simulate
    this.
    You aggregate in the scratchpad and then collapse using a MAX().

    Cheers
    Serge


    Serge Rielau Guest

  2. #2

    Default Re: Column UDFs

    Actually I don't think this is much of a problem.

    You can use ORDER BY and ORDER BY ORDER OF which shoudl be sufficient to
    geep the
    values grouped as they flow by.
    First call is indeed the first call for the execution of the statement.
    But the scratchpad an remember the current group and re-initialize whne the
    group changes.

    Cheers
    Serge


    Serge Rielau Guest

  3. #3

    Default Re: Column UDFs

    One concern is the performance/scalability impact of the strategy of
    essentially doing the grouping within the udf.

    (1) Performance -- The UDF has to produce a result on each call as if the
    group for the key it was called with is over. This may be
    quite an overhead, at least for some functions.

    (2) Scalability -- Parallel execution will be off.

    Does anyone have experience with the performance and scalability effects
    such as by implementing MAX as a column UDF and comparing with the built-in MAX?

    Is there any plan to support column UDFs similar to Oracle's aggregate
    functions? If so, when?

    -Waqar
    Waqar Hasan Guest

  4. #4

    Default Re: Column UDFs

    >>>>> "WG" == W Gemini <W> writes:

    WG> I'd be very careful with this approach, it would not working
    WG> in parallel environment. I think the right approach is to
    WG> scream to your sales representative and ask for this
    WG> feature. If enough people shouted, chances are somebody would
    WG> listen evetually.

    Oh I totally agree. What we need is user-defined aggregates.

    Unless enough people scream it won't bubble up as a priority.

    --
    Pip-pip
    Sailesh
    [url]http://www.cs.berkeley.edu/~sailesh[/url]

    Sailesh Krishnamurthy Guest

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