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  1. Clint Vosloo

    Hi Mark Mumy,

    Thanks so much for putting the post up. As a long time Sybase IQ user it is great to see it getting some air time in the SAP space now.

    Two quick questions based off an Advanced Tuning workshop I went to on version 15.

    1. I was under the impression that the threshold to move from LF to HG indexing was closer to the 10 000 mark in terms of uniqueness instead of 2000 ?
    2. I was also advised to stop using HNG indexes

    Really would appreciate your insight here

    Thanks

    Clint

    P.S. –> Thanks also for your sizing guide that I have used frequently over the years.. 🙂

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    1. Mark Mumy Post author

      Hi Clint Vosloo,

      There are two thresholds with LF indexes.  First, you have the absolute max.  The max is 9999 values.  Second, you have the usable limit.  This is the value that is open to interpretation and experience.  My preference is in the 1500-2000 range.  That isn’t an absolute, though, so feel free to play around with this.

      I, generally, advise against using HNG indexes, too.  Most of this logic is done in other index structures.  Also, the other indexes (HG, LF, n-bit) can allow for better performance in terms of parallelism, etc.  To be honest, I haven’t done a POC in the last 3+ years where I found that having an HNG index greatly improved performance.  Like the LF index threshold, this is open to interpretation and experience.  I would say that you try it out to see how your system reacts to having them or not.  My experience would show that likely you won’t see significant improvement. 

      Mark

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