[GitHub] [spark] cloud-fan commented on a change in pull request #24102: [SPARK-27171][SQL] Support Full-Partitons scan in limit for the first time

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cloud-fan commented on a change in pull request #24102: [SPARK-27171][SQL] Support Full-Partitons scan in limit for the first time
URL: https://github.com/apache/spark/pull/24102#discussion_r266320830
 
 

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 File path: sql/core/src/main/scala/org/apache/spark/sql/execution/SparkPlan.scala
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 @@ -344,7 +344,7 @@ abstract class SparkPlan extends QueryPlan[SparkPlan] with Logging with Serializ
     while (buf.size < n && partsScanned < totalParts) {
       // The number of partitions to try in this iteration. It is ok for this number to be
       // greater than totalParts because we actually cap it at totalParts in runJob.
-      var numPartsToTry = 1L
+      var numPartsToTry = Math.max(Math.ceil(sqlContext.conf.limitStartUpFactor * totalParts).toLong, 1L)
 
 Review comment:
   How much perf speed up you observed for your query?

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