Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/13773#discussion_r67775871
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/jdbc/JDBCRelation.scala
---
@@ -52,29 +52,44 @@ private[sql] object JDBCRelation {
* @return an array of partitions with where clause for each partition
*/
def columnPartition(partitioning: JDBCPartitioningInfo):
Array[Partition] = {
- if (partitioning == null) return Array[Partition](JDBCPartition(null,
0))
+ if (partitioning == null || partitioning.numPartitions <= 1 ||
+ partitioning.lowerBound == partitioning.upperBound) {
+ return Array[Partition](JDBCPartition(null, 0))
+ }
- val numPartitions = partitioning.numPartitions
- val column = partitioning.column
- if (numPartitions == 1) return Array[Partition](JDBCPartition(null, 0))
+ val lowerBound = partitioning.lowerBound
+ val upperBound = partitioning.upperBound
+ require (lowerBound <= upperBound,
+ "Operation not allowed: the lower bound of partitioning column is
larger than the upper " +
+ s"bound. Lower bound: $lowerBound; Upper bound: $upperBound")
+
+ val numPartitions =
+ if ((upperBound - lowerBound) >= partitioning.numPartitions) {
+ partitioning.numPartitions
+ } else {
+ upperBound - lowerBound
+ }
// Overflow and silliness can happen if you subtract then divide.
// Here we get a little roundoff, but that's (hopefully) OK.
- val stride: Long = (partitioning.upperBound / numPartitions
- - partitioning.lowerBound / numPartitions)
+ val stride: Long = upperBound / numPartitions - lowerBound /
numPartitions
+ // The automatic adjustment of numPartitions can ensure the following
checking condition.
+ assert(stride >= 1, "The specified number of partitions should be
greater than " +
--- End diff --
actually i think this assert is pretty dangerous -- doesn't this make it
fail if the number of partitions is 10, and the total value difference is less
than 10?
I'd argue there is nothing inherently wrong in that case and break old
code. I'd consider logging a warning (and include the actual value for stride
and lower/upper bound)
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