Github user tejasapatil commented on a diff in the pull request:
https://github.com/apache/spark/pull/16898#discussion_r100697403
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/FileFormatWriter.scala
---
@@ -134,8 +142,26 @@ object FileFormatWriter extends Logging {
// prepares the job, any exception thrown from here shouldn't cause
abortJob() to be called.
committer.setupJob(job)
+ val bucketIdExpression = bucketSpec.map { spec =>
+ // Use `HashPartitioning.partitionIdExpression` as our bucket id
expression, so that we can
+ // guarantee the data distribution is same between shuffle and
bucketed data source, which
+ // enables us to only shuffle one side when join a bucketed table
and a normal one.
+ HashPartitioning(bucketColumns,
spec.numBuckets).partitionIdExpression
+ }
+ // We should first sort by partition columns, then bucket id, and
finally sorting columns.
+ val requiredOrdering = (partitionColumns ++ bucketIdExpression ++
sortColumns)
+ .map(SortOrder(_, Ascending))
+ val actualOrdering = queryExecution.executedPlan.outputOrdering
+ // We can still avoid the sort if the required ordering is [partCol]
and the actual ordering
+ // is [partCol, anotherCol].
+ val rdd = if (requiredOrdering ==
actualOrdering.take(requiredOrdering.length)) {
--- End diff --
You could do semantic equals and not object equals. I recall using object
equals in in `EnsureRequirements` was adding unnecessary SORT in some cases :
https://github.com/apache/spark/pull/14841/files#diff-cdb577e36041e4a27a605b6b3063fd54
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