konstantinb commented on code in PR #6505:
URL: https://github.com/apache/hive/pull/6505#discussion_r4475452013
##########
ql/src/java/org/apache/hadoop/hive/ql/optimizer/stats/annotation/StatsRulesProcFactory.java:
##########
@@ -1381,6 +1384,16 @@ private long evaluateChildExpr(Statistics stats,
ExprNodeDesc child,
return numRows / 2;
}
+ private static long rowsAfterEqualityFilter(long numRows, long dvs) {
+ if (dvs < 0) {
+ return numRows / 2;
+ }
+ if (dvs == 0) {
+ return 0;
Review Comment:
Fixed in
[dcaac90](https://github.com/apache/hive/pull/6505/commits/dcaac90c35) for the
case this PR introduced: a verified-zero NDV means every row is NULL, so col
<=> NULL (either operand order) now keeps all rows. Unknown and known NDVs keep
master's estimates; using numNulls there too would change master's behavior, so
that's left for a follow-up.
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