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https://issues.apache.org/jira/browse/SPARK-3036?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14102033#comment-14102033
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Apache Spark commented on SPARK-3036:
-------------------------------------
User 'ueshin' has created a pull request for this issue:
https://github.com/apache/spark/pull/2032
> Add MapType containing null value support to Parquet.
> -----------------------------------------------------
>
> Key: SPARK-3036
> URL: https://issues.apache.org/jira/browse/SPARK-3036
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Reporter: Takuya Ueshin
> Priority: Blocker
>
> Current Parquet schema for {{MapType}} is as follows regardless of
> {{valueContainsNull}}:
> {noformat}
> message root {
> optional group a (MAP) {
> repeated group map (MAP_KEY_VALUE) {
> required int32 key;
> required int32 value;
> }
> }
> }
> {noformat}
> and if the map contains {{null}} value, it throws runtime exception.
> To handle {{MapType}} containing {{null}} value, the schema should be as
> follows if {{valueContainsNull}} is {{true}}:
> {noformat}
> message root {
> optional group a (MAP) {
> repeated group map (MAP_KEY_VALUE) {
> required int32 key;
> optional int32 value;
> }
> }
> }
> {noformat}
> FYI:
> Hive's Parquet writer *always* uses the latter schema, but reader can read
> from both schema.
> NOTICE:
> This change will break backward compatibility when the schema is read from
> Parquet metadata ({{"org.apache.spark.sql.parquet.row.metadata"}}).
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