ming535 commented on code in PR #2823:
URL: https://github.com/apache/arrow-datafusion/pull/2823#discussion_r913716649
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datafusion/optimizer/src/eliminate_limit.rs:
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@@ -35,35 +39,98 @@ impl EliminateLimit {
}
}
+/// Ancestor indicates the current ancestor in the LogicalPlan tree
+/// when traversing down related to "eliminate limit".
+enum Ancestor {
+ /// Limit
+ FromLimit { skip: Option<usize> },
+ /// Other nodes that don't affect the adjustment of "Limit"
+ NotRelevant,
+}
+
+/// replaces LIMIT 0 with an [LogicalPlan::EmptyRelation]
+/// replaces LIMIT node whose ancestor LIMIT's skip is greater than or equal
to current's fetch
+/// with an [LogicalPlan::EmptyRelation]
+fn eliminate_limit(
+ _optimizer: &EliminateLimit,
+ ancestor: &Ancestor,
+ plan: &LogicalPlan,
+ _optimizer_config: &OptimizerConfig,
+) -> Result<LogicalPlan> {
+ match plan {
Review Comment:
`SELECT * FROM (SELECT * FROM test_a LIMIT 5) AS test_b OFFSET 5;`
In the above query, the current plan is the one with only `fetch` (the
subquery).
I thought when the current node is `Limit` with only `skip`, it should be
handled the same as `Projection`, `Sort`.
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