GitHub user clockfly opened a pull request:
https://github.com/apache/spark/pull/14973
[SPARK-17356][SQL][1.6] Fix out of memory issue when generating JSON for
TreeNode
This is a backport of PR https://github.com/apache/spark/pull/14915 to
branch 1.6.
## What changes were proposed in this pull request?
class `org.apache.spark.sql.types.Metadata` is widely used in mllib to
store some ml attributes. `Metadata` is commonly stored in `Alias` expression.
```
case class Alias(child: Expression, name: String)(
val exprId: ExprId = NamedExpression.newExprId,
val qualifier: Option[String] = None,
val explicitMetadata: Option[Metadata] = None,
override val isGenerated: java.lang.Boolean = false)
```
The `Metadata` can take a big memory footprint since the number of
attributes is big ( in scale of million). When `toJSON` is called on `Alias`
expression, the `Metadata` will also be converted to a big JSON string.
If a plan contains many such kind of `Alias` expressions, it may trigger
out of memory error when `toJSON` is called, since converting all `Metadata`
references to JSON will take huge memory.
With this PR, we will skip scanning Metadata when doing JSON conversion.
For a reproducer of the OOM, and analysis, please look at jira
https://issues.apache.org/jira/browse/SPARK-17356.
## How was this patch tested?
Existing tests.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/clockfly/spark json_oom_1.6
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/14973.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #14973
----
commit 0b22ec689a7534c555d1a3c623f817f788163ca3
Author: Sean Zhong <seanzh...@databricks.com>
Date: 2016-09-06T09:26:41Z
[SPARK-17369][SQL] MetastoreRelation toJSON throws AssertException due to
missing otherCopyArgs
## What changes were proposed in this pull request?
`TreeNode.toJSON` requires a subclass to explicitly override otherCopyArgs
to include currying construction arguments, otherwise it reports
AssertException telling that the construction argument values' count doesn't
match the construction argument names' count.
For class `MetastoreRelation`, it has a currying construction parameter
`client: HiveClient`, but Spark forgets to add it to the list of otherCopyArgs.
## How was this patch tested?
Unit tests.
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