Multiple Index Regression Analysis

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10 Responses

  1. Isaac Munoz says:

    Hi Ember this is a very nice article, thanks for sharing it !!.

    After you run db2advis you can also get the explain plan of the query with the recommended/new indexes. In this case you didn’t copy/paste it but I wonder; most likely the big new index (IDX1505210120080) is used in a join with another table. Don’t you think maybe by creating an index using only the column(s) joined with that other table could provide a good result (timerons) without including the rest of the columns?. Cause normally DB2 will only suggest such huge indexes to do an index-scan…. but I guess the most important thing is to optimize the join.

    Regards

    • Ember Crooks says:

      Absolutely, there is additional analysis I could do as to which columns in that index are truly necessary. Would probably make a good separate blog entry.

  2. Norman Wong says:

    You can do this from Data Studio and the Query Tuner. After the Index Advisor is run, you Test Candidate indexes by running explain with different combinations of indexes added or removed. You can then do a graph compares to see which indexes helped the most.

    • Ember Crooks says:

      Is the Query Tuner a pay-to-use tool? Not a fan of GUIs, so don’t use them much.

      • Manohar says:

        Even Im not but i recently tried my hands on the Query Tuner in IBM DS, believe me its generating an awesome report. Yeah i agree its basically drawing the data from explain information but html report its generating on a consolidated basis can be used for further discussion with the developers and RCA.

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