englefly commented on code in PR #18784:
URL: https://github.com/apache/doris/pull/18784#discussion_r1196253606
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fe/fe-core/src/main/java/org/apache/doris/nereids/stats/StatsCalculator.java:
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@@ -464,6 +478,32 @@ private Statistics computeTopN(TopN topN) {
return stats.withRowCount(Math.min(stats.getRowCount(),
topN.getLimit()));
}
+ private Statistics computePartitionTopN(PartitionTopN partitionTopN) {
+ Statistics stats = groupExpression.childStatistics(0);
+ double rowCount = stats.getRowCount();
+ List<Expression> partitionKeys = partitionTopN.getPartitionKeys();
+ if (!partitionTopN.hasGlobalLimit() && !partitionKeys.isEmpty()) {
Review Comment:
`select * from (select * ,rank() over(partition by b order by a) as num
from t ) tt where num < 10;`
rank() column stats should be set manually, its max is 10. And hence, outer
filter `num<10` selectivity is 1.
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