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https://issues.apache.org/jira/browse/TRAFODION-2349?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Hans Zeller updated TRAFODION-2349:
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Description:
When we introduce a temp table, we want to "transplant" the statistics from the
original query tree representing the common subexpression to the new scan and
its ancestors. This requires two mappings, one from the original tree to the
temp table columns, the other from the temp table cols to the characteristic
outputs of the MapValueIds above the temp scan.
While most of these mappings are done in terms of VEGRefs, the statistics use
BaseColumns instead. Right now, we map the BaseColumns of single column stats
to VEGRefs in the new tree. We might be able to do the same for MC stats. Or,
alternatively, we may need to decided on specific BaseColumns to map to.
See methods Scan::synthEstLogProp() and MapValueIds::synthEstLogProp().
was:
When we introduce a temp table, we want to "transplant" the statistics from the
original query tree representing the common subexpression to the new scan and
its ancestors. This requires two mappings, one from the original tree to the
temp table columns, the other from the temp table cols to the characteristic
outputs of the MapValueIds above the temp scan.
While most of these mappings are done in terms of VEGRefs, the statistics use
BaseColumns instead. Right now, we map the BaseColumns of single column stats
to VEGRefs in the new tree. We might be able to do the same for MC stats. Or,
alternatively, we may need to decided on specific BaseColumns to map to.
See methods
> Solve issue with mapping of value ids for statistics for common subexpr
> -----------------------------------------------------------------------
>
> Key: TRAFODION-2349
> URL: https://issues.apache.org/jira/browse/TRAFODION-2349
> Project: Apache Trafodion
> Issue Type: Sub-task
> Components: sql-cmp
> Affects Versions: 2.1-incubating
> Reporter: Hans Zeller
> Assignee: Hans Zeller
>
> When we introduce a temp table, we want to "transplant" the statistics from
> the original query tree representing the common subexpression to the new scan
> and its ancestors. This requires two mappings, one from the original tree to
> the temp table columns, the other from the temp table cols to the
> characteristic outputs of the MapValueIds above the temp scan.
> While most of these mappings are done in terms of VEGRefs, the statistics use
> BaseColumns instead. Right now, we map the BaseColumns of single column stats
> to VEGRefs in the new tree. We might be able to do the same for MC stats.
> Or, alternatively, we may need to decided on specific BaseColumns to map to.
> See methods Scan::synthEstLogProp() and MapValueIds::synthEstLogProp().
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