[jira] [Commented] (SPARK-10395) Simplify CatalystReadSupport

["Apache Spark (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-10395?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14725175#comment-14725175 ] 

Apache Spark commented on SPARK-10395:
--------------------------------------

User 'liancheng' has created a pull request for this issue:
https://github.com/apache/spark/pull/8553

> Simplify CatalystReadSupport
> ----------------------------
>
>                 Key: SPARK-10395
>                 URL: https://issues.apache.org/jira/browse/SPARK-10395
>             Project: Spark
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 1.5.0
>            Reporter: Cheng Lian
>            Assignee: Cheng Lian
>            Priority: Minor
>
> The API interface of Parquet {{ReadSupport}} is a little bit over complicated because of historical reasons.  In older versions of parquet-mr (say 1.6.0rc3 and prior), {{ReadSupport}} need to be instantiated and initialized twice on both driver side and executor side.  The {{init()}} method is for driver side initialization, while {{prepareForRead()}} is for executor side.  However, starting from parquet-mr 1.6.0, it's no longer the case, and {{ReadSupport}} is only instantiated and initialized on executor side.  So, theoretically, now it's totally fine to combine these two methods into a single initialization method.  The only reason (I could think of) to still have them here is for parquet-mr API backwards-compatibility.
> Due to this reason, we no longer need to rely on {{ReadContext}} to pass requested schema from {{init()}} to {{prepareForRead()}}, using a private `var` for requested schema in {{CatalystReadSupport}} would be enough.
> Another thing is that, after removing the old Parquet support code, now we always set Catalyst requested schema properly when reading Parquet files.  So all those "fallback" logic in {{CatalystReadSupport}} is now redundant.



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