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https://issues.apache.org/jira/browse/TRAFODION-2661?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16075483#comment-16075483
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ASF GitHub Bot commented on TRAFODION-2661:
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Github user asfgit closed the pull request at:
https://github.com/apache/incubator-trafodion/pull/1146
> MDAM not chosen for OR predicate of leading index column
> --------------------------------------------------------
>
> Key: TRAFODION-2661
> URL: https://issues.apache.org/jira/browse/TRAFODION-2661
> Project: Apache Trafodion
> Issue Type: Bug
> Components: sql-cmp
> Affects Versions: 2.0-incubating
> Reporter: Hans Zeller
> Assignee: David Wayne Birdsall
>
> We saw the following issue in a customer scenario:
> SELECT SUM(c)
> from tbl2
> where a in ('A','B')
> AND b >= '8';
> The table has a salted index on column a. That index has many more columns
> (13 in this case, including the salt column).
> The plan we would expect is an MDAM plan with no predicate on _SALT_ and the
> OR predicate on column a.
> However, we get a full index scan (we can use an index-only scan in this
> case).
> When we force an MDAM plan, we see a vastly higher cost (250,000 in our
> example) than for the single subset plan (cost of 9 in our example).
> Dave has already mentioned that this has to do with RangeSpecs. The following
> workaround gives the MDAM plan for us:
> cqd RANGESPEC_TRANSFORMATION 'off';
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