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Posted to issues@spark.apache.org by "Apache Spark (Jira)" <ji...@apache.org> on 2020/05/17 21:36:00 UTC
[jira] [Commented] (SPARK-27217) Nested schema pruning doesn't work
for aggregation e.g. `sum`.
[ https://issues.apache.org/jira/browse/SPARK-27217?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17109669#comment-17109669 ]
Apache Spark commented on SPARK-27217:
--------------------------------------
User 'viirya' has created a pull request for this issue:
https://github.com/apache/spark/pull/28560
> Nested schema pruning doesn't work for aggregation e.g. `sum`.
> --------------------------------------------------------------
>
> Key: SPARK-27217
> URL: https://issues.apache.org/jira/browse/SPARK-27217
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Affects Versions: 3.0.0
> Reporter: colin fang
> Priority: Major
>
> Since SPARK-4502 is fixed, I would expect queries such as `select sum(b.x)` doesn't have to read other nested fields.
> {code:python}
> rdd = spark.range(1000).rdd.map(lambda x: [x.id+3, [x.id+1, x.id-1]])
> df = spark.createDataFrame(add, schema='a:int,b:struct<x:int,y:int>')
> df.repartition(1).write.mode('overwrite').parquet('test.parquet')
> df = spark.read.parquet('test.parquet')
> spark.conf.set('spark.sql.optimizer.nestedSchemaPruning.enabled', 'true')
> df.select('b.x').explain()
> # ReadSchema: struct<b:struct<x:int>>
> spark.conf.set('spark.sql.optimizer.nestedSchemaPruning.enabled', 'false')
> df.select('b.x').explain()
> # ReadSchema: struct<b:struct<x:int,y:int>>
> spark.conf.set('spark.sql.optimizer.nestedSchemaPruning.enabled', 'true')
> df.selectExpr('sum(b.x)').explain()
> # ReadSchema: struct<b:struct<x:int,y:int>>
> {code}
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