englefly commented on code in PR #29184:
URL: https://github.com/apache/doris/pull/29184#discussion_r1437321450
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fe/fe-core/src/main/java/org/apache/doris/nereids/stats/FilterEstimation.java:
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@@ -568,10 +570,28 @@ public Statistics visitLike(Like like, EstimationContext
context) {
"col stats not found. slot=%s in %s",
like.left().toSql(), like.toSql());
ColumnStatisticBuilder colBuilder = new
ColumnStatisticBuilder(origin);
- colBuilder.setNdv(origin.ndv *
DEFAULT_LIKE_COMPARISON_SELECTIVITY).setNumNulls(0);
+ double notNullNdv = getNotNullSelectivity(origin, origin.ndv *
DEFAULT_LIKE_COMPARISON_SELECTIVITY);
+ colBuilder.setNdv(origin.ndv * DEFAULT_LIKE_COMPARISON_SELECTIVITY)
+ .setCount(notNullNdv *
context.statistics.getRowCount()).setNumNulls(0);
statsBuilder.putColumnStatistics(like.left(), colBuilder.build());
context.addKeyIfSlot(like.left());
}
return statsBuilder.build();
}
+
+ private double getNotNullSelectivity(ColumnStatistic stats, double
origSel) {
+ double rowCount = stats.count;
+ double numNulls = stats.numNulls;
+ double ndv = stats.ndv;
+ if (numNulls > rowCount - ndv) {
+ numNulls = rowCount - ndv > 0 ? rowCount - ndv : 0;
Review Comment:
"numNulls = rowCount-ndv" this is not true.
consider col values (1, 1, 1, null)
rowcount=4, ndv=1
then we get numNulls = 4-1=3, but it is 1
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