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https://issues.apache.org/jira/browse/SPARK-32694?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17184614#comment-17184614
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Chao Sun commented on SPARK-32694:
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Thanks [~rakson] for the pointer! didn't know there were multiple attempts on
this issue in the past. I'll think more on what is the best approach to move
this forward.
> Pushdown cast to data sources
> -----------------------------
>
> Key: SPARK-32694
> URL: https://issues.apache.org/jira/browse/SPARK-32694
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 3.0.0
> Reporter: Chao Sun
> Priority: Major
>
> Currently we don't support pushing down cast to data source (see
> [link|http://apache-spark-developers-list.1001551.n3.nabble.com/SparkSql-Casting-of-Predicate-Literals-tp29956p30035.html]
> for a discussion). For instance, in the following code snippet:
> {code}
> scala> case class Person(name: String, age: Short)
> scala> Seq(Person("John", 32), Person("David", 25), Person("Mike",
> 18)).toDS().write.parquet("/tmp/person.parquet")
> scala> val personDS = spark.read.parquet("/tmp/person.parquet")
> scala> personDS.createOrReplaceTempView("person")
> scala> spark.sql("SELECT * FROM person where age < 30")
> {code}
> The predicate won't be pushed down to Parquet data source because in
> {{DataSourceStrategy}}, {{PushableColumnBase}} only handles a few limited
> cases such as {{Attribute}} and {{GetStructField}}. Potentially we can handle
> {{Cast}} here as well.
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