morrySnow commented on code in PR #51928:
URL: https://github.com/apache/doris/pull/51928#discussion_r2166298453
##########
fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/ScalarSubquery.java:
##########
@@ -122,13 +129,38 @@ public ScalarSubquery withSubquery(LogicalPlan subquery) {
}
/**
- * for correlated subquery, we define top level scalar agg as if it meets
the both 2 conditions:
- * 1. The agg or its child contains correlated slots
+ * get query plan output slot, adjust it to
+ * 1. true(no adjust), when it has top agg, and the agg function is
NotNullableAggregateFunction
+ * for example: `t1.a = (select count(t2.x) from t2)`, count(t2.x) is
always not null, even if t2 contain 0 row
+ * 2. false, otherwise.
+ * for example: `t1.a = (select t2.y from t2 limit 1)`, even if t2.y
is not nullable, but if t2 contain 0 row,
+ * the sub query t2 output is still null.
+ */
+ public Slot getOutputSlotAdjustNullable() {
+ Slot output = queryPlan.getOutput().get(0);
+ boolean nullable = true;
+ Optional<NamedExpression> aggOpt = getTopLevelScalarAggFunction();
Review Comment:
could this be lazy memorize to avoid compute multi times?
##########
fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/ScalarSubquery.java:
##########
@@ -122,13 +129,38 @@ public ScalarSubquery withSubquery(LogicalPlan subquery) {
}
/**
- * for correlated subquery, we define top level scalar agg as if it meets
the both 2 conditions:
- * 1. The agg or its child contains correlated slots
+ * get query plan output slot, adjust it to
+ * 1. true(no adjust), when it has top agg, and the agg function is
NotNullableAggregateFunction
+ * for example: `t1.a = (select count(t2.x) from t2)`, count(t2.x) is
always not null, even if t2 contain 0 row
+ * 2. false, otherwise.
+ * for example: `t1.a = (select t2.y from t2 limit 1)`, even if t2.y
is not nullable, but if t2 contain 0 row,
+ * the sub query t2 output is still null.
+ */
+ public Slot getOutputSlotAdjustNullable() {
Review Comment:
add some fe ut to cover these functions
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