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Posted to commits@spark.apache.org by li...@apache.org on 2016/09/22 15:25:39 UTC
spark git commit: [SQL][MINOR] correct the comment of
SortBasedAggregationIterator.safeProj
Repository: spark
Updated Branches:
refs/heads/master 72d9fba26 -> 8a02410a9
[SQL][MINOR] correct the comment of SortBasedAggregationIterator.safeProj
## What changes were proposed in this pull request?
This comment went stale long time ago, this PR fixes it according to my understanding.
## How was this patch tested?
N/A
Author: Wenchen Fan <we...@databricks.com>
Closes #15095 from cloud-fan/update-comment.
Project: http://git-wip-us.apache.org/repos/asf/spark/repo
Commit: http://git-wip-us.apache.org/repos/asf/spark/commit/8a02410a
Tree: http://git-wip-us.apache.org/repos/asf/spark/tree/8a02410a
Diff: http://git-wip-us.apache.org/repos/asf/spark/diff/8a02410a
Branch: refs/heads/master
Commit: 8a02410a92429bff50d6ce082f873cea9e9fa91e
Parents: 72d9fba
Author: Wenchen Fan <we...@databricks.com>
Authored: Thu Sep 22 23:25:32 2016 +0800
Committer: Cheng Lian <li...@databricks.com>
Committed: Thu Sep 22 23:25:32 2016 +0800
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.../aggregate/SortBasedAggregationIterator.scala | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
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http://git-wip-us.apache.org/repos/asf/spark/blob/8a02410a/sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/SortBasedAggregationIterator.scala
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diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/SortBasedAggregationIterator.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/SortBasedAggregationIterator.scala
index 3f7f849..c2b1ef0 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/SortBasedAggregationIterator.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/SortBasedAggregationIterator.scala
@@ -86,8 +86,15 @@ class SortBasedAggregationIterator(
// The aggregation buffer used by the sort-based aggregation.
private[this] val sortBasedAggregationBuffer: MutableRow = newBuffer
- // A SafeProjection to turn UnsafeRow into GenericInternalRow, because UnsafeRow can't be
- // compared to MutableRow (aggregation buffer) directly.
+ // This safe projection is used to turn the input row into safe row. This is necessary
+ // because the input row may be produced by unsafe projection in child operator and all the
+ // produced rows share one byte array. However, when we update the aggregate buffer according to
+ // the input row, we may cache some values from input row, e.g. `Max` will keep the max value from
+ // input row via MutableProjection, `CollectList` will keep all values in an array via
+ // ImperativeAggregate framework. These values may get changed unexpectedly if the underlying
+ // unsafe projection update the shared byte array. By applying a safe projection to the input row,
+ // we can cut down the connection from input row to the shared byte array, and thus it's safe to
+ // cache values from input row while updating the aggregation buffer.
private[this] val safeProj: Projection = FromUnsafeProjection(valueAttributes.map(_.dataType))
protected def initialize(): Unit = {
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