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Hans Zeller commented on TRAFODION-2349: ---------------------------------------- Part of this was addressed by https://github.com/apache/incubator-trafodion/pull/928. This fixed many issues with single column stats, but there is still some work missing for multi-column stats. > 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 > Fix For: 2.2-incubating > > > 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(). -- This message was sent by Atlassian JIRA (v6.3.15#6346)