wangyum edited a comment on pull request #31739:
URL: https://github.com/apache/spark/pull/31739#issuecomment-805359628
> Last question: do we push down limit through project?
It seems push down limit through project no benefit:
```scala
spark.range(2000L).selectExpr("id AS a", "id AS b").write.saveAsTable("t1")
spark.sql("select a, java_method('java.lang.Thread', 'sleep', 3000L) from t1
limit 5").show()
spark.sql("select a, java_method('java.lang.Thread', 'sleep', 3000L) from
(select * from t1 limit 5) t limit 5").show()
```
```
== Optimized Logical Plan ==
GlobalLimit 5
+- LocalLimit 5
+- Project [a#16L, java_method(java.lang.Thread, sleep, 3000) AS
java_method(java.lang.Thread, sleep, 3000)#18]
+- Relation default.t1[a#16L,b#17L] parquet
```
```
== Optimized Logical Plan ==
Project [a#16L, java_method(java.lang.Thread, sleep, 3000) AS
java_method(java.lang.Thread, sleep, 3000)#21]
+- GlobalLimit 5
+- LocalLimit 5
+- Project [a#16L]
+- Relation default.t1[a#16L,b#17L] parquet
```
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