yujun777 commented on code in PR #62742:
URL: https://github.com/apache/doris/pull/62742#discussion_r3354691735
##########
fe/fe-core/src/main/java/org/apache/doris/nereids/rules/rewrite/AddProjectForVolatileExpression.java:
##########
@@ -269,6 +271,85 @@ public <T extends Expression> Optional<Pair<List<T>,
LogicalProject<Plan>>> rewr
return Optional.of(Pair.of(newTargetsBuilder.build(), new
LogicalProject<>(projects, plan.child(0))));
}
+ private Optional<JoinRewriteResult>
rewriteJoinExpressions(LogicalJoin<Plan, Plan> join,
+ Collection<Expression> targets) {
+ Map<Expression, Integer> volatileExpressionCounter =
Maps.newLinkedHashMap();
+ Map<Expression, Set<Slot>> volatileExpressionSlots =
Maps.newLinkedHashMap();
+ for (Expression target : targets) {
+ target.foreach(e -> {
+ Expression expr = (Expression) e;
+ if (expr.isVolatile()) {
+ volatileExpressionCounter.merge(expr, 1, Integer::sum);
+ Set<Slot> inputSlots = expr.getInputSlots();
+ volatileExpressionSlots
+ .computeIfAbsent(expr, ignored ->
Sets.newLinkedHashSet())
+ .addAll(inputSlots.isEmpty() ?
target.getInputSlots() : inputSlots);
+ }
+ });
+ }
+
+ ImmutableList.Builder<NamedExpression> leftAliases =
ImmutableList.builder();
+ ImmutableList.Builder<NamedExpression> rightAliases =
ImmutableList.builder();
+ Map<Expression, Slot> replaceMap = Maps.newHashMap();
+ Set<Slot> leftOutputSet = join.left().getOutputSet();
+ Set<Slot> rightOutputSet = join.right().getOutputSet();
+ for (Entry<Expression, Integer> entry :
volatileExpressionCounter.entrySet()) {
+ if (entry.getValue() <= 1) {
+ continue;
Review Comment:
这个是没办法的。如果rand() 不下推， 留在join 上，此时这个rand() 被错误计算两次了，这种情况更加不可接受。相比rand()
被错误计算两次， 下推到任何一边的结果都是更加可接受的
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