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Posted to issues-all@impala.apache.org by "Quanlong Huang (Jira)" <ji...@apache.org> on 2026/07/15 08:31:00 UTC

[jira] [Created] (IMPALA-15182) Uses HBO AggregationNode Cardinality in Expr.getNumDistinctValues

Quanlong Huang created IMPALA-15182:
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             Summary: Uses HBO AggregationNode Cardinality in Expr.getNumDistinctValues
                 Key: IMPALA-15182
                 URL: https://issues.apache.org/jira/browse/IMPALA-15182
             Project: IMPALA
          Issue Type: Improvement
            Reporter: Quanlong Huang
            Assignee: Quanlong Huang


Expr.getNumDistinctValues() returns the ndv for an Expr or a list of Exprs. We can use the HBO stats on AggregationNode cardinalities to improve this.
[https://github.com/apache/impala/blob/21cd965f1670580f96d0ea846d9a2e83f66a2176/fe/src/main/java/org/apache/impala/analysis/Expr.java#L944-L956]
[https://github.com/apache/impala/blob/21cd965f1670580f96d0ea846d9a2e83f66a2176/fe/src/main/java/org/apache/impala/analysis/Expr.java#L633]

If the HMS stats are missing, we can use HBO stats for column ndvs at
[https://github.com/apache/impala/blob/21cd965f1670580f96d0ea846d9a2e83f66a2176/fe/src/main/java/org/apache/impala/analysis/SlotRef.java#L179]



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