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https://issues.apache.org/jira/browse/CALCITE-3963?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17119807#comment-17119807
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Julian Hyde commented on CALCITE-3963:
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I don't like the 'statistics confidence level' concept. There will be ties
(especially since there are only 4 values). And there will be non-deterministic
and arbitrary behavior. Especially when you merge sets.
What's wrong with my suggestion to treat all RelNode instances in a set as
equivalent? Use an order-independent (and monotonic) folding operations such as
'min', 'max', 'union' to combine property values.
I also don't want to bless the "logical node" concept with a class. The class
LogicalNode has a circular definition.
Some properties may turn out to be dependent on certain traits but independent
of others (e.g. whether a RelNode is sorted on a key will depend on how it is
partitioned). Thus logical vs physical is a gray area.
> Maintain logical properties at RelSet (equivalent group) instead of RelNode
> ---------------------------------------------------------------------------
>
> Key: CALCITE-3963
> URL: https://issues.apache.org/jira/browse/CALCITE-3963
> Project: Calcite
> Issue Type: Bug
> Reporter: Xiening Dai
> Assignee: Xiening Dai
> Priority: Major
>
> Currently the logical properties (such as row count, distinct row count, etc)
> are maintained at RelNode level. This creates a number of meta data
> consistency problems, e.g. CALCITE-1048, CALCITE-2166.
> In theory, all RelNodes in a RelSet should share the same logical properties
> per definition of relational equivalence. So it makes more sense to keep
> logical properties at RelSet level, rather than the RelNode. And such
> properties shouldn't change when new sub set is created or subset's best is
> changed.
> Specifically I think below build in metadata should fall into the logical
> properties category -
> Selectivity
> UniqueKeys
> ColumnUniqueness
> RowCount
> MaxRowCount
> MinRowCount
> DistinctRowCount
> Size (averageRowSize, averageColumnSize)
>
>
>
>
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