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https://issues.apache.org/jira/browse/PARQUET-2069?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17542153#comment-17542153
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ASF GitHub Bot commented on PARQUET-2069:
-----------------------------------------
islamismailov commented on PR #957:
URL: https://github.com/apache/parquet-mr/pull/957#issuecomment-1137620395
I debugged this some more and it looks like some of the problem is coming
from conversion between parquet and avro. Especially if you read parquetSchema,
convert it to avro and set projection in avro schema format, it would get
converted back to parquet and it will look different from the original.
`System.out.println("ORIGINAL PARQUET " + fileSchema);
Schema avroSchema = new
AvroSchemaConverter(configuration).convert(fileSchema);
MessageType parquetSchema = new
AvroSchemaConverter(configuration).convert(avroSchema);
System.out.println("RECONSTRUCTED PARQUET " + parquetSchema);`
> Parquet file containing arrays, written by Parquet-MR, cannot be read again
> by Parquet-MR
> -----------------------------------------------------------------------------------------
>
> Key: PARQUET-2069
> URL: https://issues.apache.org/jira/browse/PARQUET-2069
> Project: Parquet
> Issue Type: Bug
> Components: parquet-avro
> Affects Versions: 1.12.0
> Environment: Windows 10
> Reporter: Devon Kozenieski
> Priority: Blocker
> Attachments: modified.parquet, original.parquet, parquet-diff.png
>
>
> In the attached files, there is one original file, and one written modified
> file that results after reading the original file and writing it back with
> Parquet-MR, with a few values modified. The schema should not be modified,
> since the schema of the input file is used as the schema to write the output
> file. However, the output file has a slightly modified schema that then
> cannot be read back the same way again with Parquet-MR, resulting in the
> exception message: java.lang.ClassCastException: optional binary element
> (STRING) is not a group
> My guess is that the issue lies in the Avro schema conversion.
> The Parquet files attached have some arrays and some nested fields.
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