jackwener commented on code in PR #20209:
URL: https://github.com/apache/doris/pull/20209#discussion_r1211529951
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fe/fe-core/src/main/java/org/apache/doris/nereids/jobs/joinorder/hypergraph/receiver/PlanReceiver.java:
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@@ -335,58 +336,106 @@ private void makeLogicalExpression(Group root) {
}
}
+ /**
+ * The top project of (T1, T2, T3) is different after reorder
+ * we need merge Project1 and Project2 as Project4 after reorder
+ * T1 join T2 join T3:
+ * Project1(a, e + f)
+ * join(a = e)
+ * Project2(a, b + d as e)
+ * join(a = c)
+ * T1(a, b)
+ * T2(c, d)
+ * T3(e, f)
+ *
+ * after reorder:
+ * T1 join T3 join T2:
+ * Project4(a, b + d + f)
+ * join(a = c)
+ * Project3(a, b, f)
+ * join(a = e)
+ * T1(a, b)
+ * T3(e, f)
+ * T2(c, d)
+ */
+ private List<NamedExpression> mergeProjections(List<NamedExpression>
childProjects,
+ List<NamedExpression> parentProjects) {
+ Map<Expression, Alias> replaceMap = childProjects.stream().filter(e ->
e instanceof Alias)
+ .collect(Collectors.toMap(NamedExpression::toSlot, e ->
(Alias) e));
+ return parentProjects.stream().map(expr -> {
+ if (expr instanceof Alias) {
+ Alias alias = (Alias) expr;
+ Expression insideExpr = alias.child();
+ Expression newInsideExpr = insideExpr.rewriteUp(e -> {
+ Alias getAlias = replaceMap.get(e);
+ return getAlias == null ? e : getAlias.child();
+ });
+ return newInsideExpr == insideExpr ? expr
+ : alias.withChildren(ImmutableList.of(newInsideExpr));
+ } else {
+ Alias getAlias = replaceMap.get(expr);
+ return getAlias == null ? expr : getAlias;
+ }
+ }).collect(ImmutableList.toImmutableList());
+ }
Review Comment:
Already exist `mergeProjections(Project childProject)`
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