github-actions[bot] commented on code in PR #64559:
URL: https://github.com/apache/doris/pull/64559#discussion_r3480949532
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fe/fe-core/src/main/java/org/apache/doris/nereids/jobs/cascades/OptimizeGroupExpressionJob.java:
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@@ -111,10 +109,10 @@ private List<Rule> getJoinRules() {
return getRuleSet().getDPHypReorderRules();
} else if (isAfterDpHyper) {
return getRuleSet().getAfterDPHypReorderRules();
- } else if (isLeftZigZagTree) {
- return getRuleSet().getLeftZigZagTreeJoinReorder();
} else if (isEnableBushyTree) {
return getRuleSet().getBushyTreeJoinReorder();
+ } else if (isLeftZigZagTree) {
Review Comment:
This branch reorder makes `enable_bushy_tree=true` override the existing
unreliable-stats fallback. When `StatsCalculator` marks the join group
unreliable because the join expressions use unknown column stats, the old code
returned `getLeftZigZagTreeJoinReorder()` before considering
`enable_bushy_tree`; the local `RuleSet` comment says that left-zig-zag is the
path used when column stats are not available, and its commute/LAsscom rules
keep the exploration constrained by row-count checks.
With the new order, the same shape now selects the full bushy rule set
whenever the session has `enable_bushy_tree=true`:
```text
Project
Join group G, G.isStatsReliable=false
Join(A, B)
C
```
That bypasses the stats-unavailable fallback and can explore/cost bushy
alternatives using unreliable stats. Please keep the `isLeftZigZagTree` branch
ahead of `isEnableBushyTree`, or only let an explicit bushy request override
the fallback when the owner group statistics are reliable.
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