xudong963 commented on code in PR #19957:
URL: https://github.com/apache/datafusion/pull/19957#discussion_r2915363185
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datafusion/common/src/stats.rs:
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@@ -660,7 +637,14 @@ impl Statistics {
col_stats.max_value =
col_stats.max_value.max(&item_col_stats.max_value);
col_stats.min_value =
col_stats.min_value.min(&item_col_stats.min_value);
col_stats.sum_value =
col_stats.sum_value.add(&item_col_stats.sum_value);
- col_stats.distinct_count = Precision::Absent;
+ // Use max as a conservative lower bound for distinct count
+ // (can't accurately merge NDV since duplicates may exist across
partitions)
Review Comment:
Looks great to me, thanks for the sweet reply.
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