[jira] [Commented] (SPARK-35003) Improve performance for reading smallint in vectorized Parquet reader

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

    [ https://issues.apache.org/jira/browse/SPARK-35003?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17317763#comment-17317763 ] 

Apache Spark commented on SPARK-35003:
--------------------------------------

User 'sunchao' has created a pull request for this issue:
https://github.com/apache/spark/pull/32104

> Improve performance for reading smallint in vectorized Parquet reader
> ---------------------------------------------------------------------
>
>                 Key: SPARK-35003
>                 URL: https://issues.apache.org/jira/browse/SPARK-35003
>             Project: Spark
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 3.2.0
>            Reporter: Chao Sun
>            Priority: Major
>
> Currently {{VectorizedRleValuesReader}} reads short in the following way:
> {code:java}
> for (int i = 0; i < n; i++) {
>   c.putShort(rowId + i, (short)data.readInteger());
> }
> {code}
> For PLAIN encoding {{readInteger}} is done via:
> {code:java}
> public final int readInteger() {
>   return getBuffer(4).getInt();
> }
> {code}
> which means it needs to repeatedly call {{slice}} buffer which is more expensive than calling it once in a big chunk and then reading the ints out.
>  



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