[jira] [Comment Edited] (ARROW-11497) [Python] pyarrow parquet writer for list does not conform with Apache Parquet specification

["Truc Lam Nguyen (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-11497?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17279166#comment-17279166 ] 

Truc Lam Nguyen edited comment on ARROW-11497 at 2/4/21, 9:11 PM:
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[~emkornfield]: I got the reason now.

[~apitrou] my understanding on apache arrow is not enough to suggest any technical solution but I think it might be a good idea.

Also for my use case as an end user, it would be good if we can be allowed to produce parquet files that are compliant to official specification.


was (Author: trucnguyenlam):
[~emkornfield]: I got the reason now.

[~apitrou] as my understanding on apache arrow is not enough to suggest any technical solution but I think it might be a good idea.

Also for my use case as an end user, it would be good if we can be allowed to produce parquet files that are compliant to official specification.

> [Python] pyarrow parquet writer for list does not conform with Apache Parquet specification
> -------------------------------------------------------------------------------------------
>
>                 Key: ARROW-11497
>                 URL: https://issues.apache.org/jira/browse/ARROW-11497
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: Python
>    Affects Versions: 3.0.0
>            Reporter: Truc Lam Nguyen
>            Priority: Major
>         Attachments: parquet-tools-meta.log
>
>
> Sorry if I don't know this feature is done deliberately, but it looks like the parquet writer for list data type does not conform to Apache Parquet list logical type specification
> According to this page: [https://github.com/apache/parquet-format/blob/master/LogicalTypes.md#lists,] list type contains 3 level where the middle level, named {{list}}, must be a repeated group with a single field named _{{element}}_
> However, in the parquet file from pyarrow writer, that single field is named _item_ instead,
> Please find below the example python code that produce a parquet file (I use pandas version 1.2.1 and pyarrow version 3.0.0) 
> {code:java}
> import pandas as pd
>  
> df = pd.DataFrame(data=[ {'studio': 'blizzard', 'games': [{'name': 'diablo', 'version': '3'}, {'name': 'star craft', 'version': '2'}]}, {'studio': 'ea', 'games': [{'name': 'fifa', 'version': '21'}]}, ])
> df.to_parquet('/tmp/test.parquet', engine='pyarrow')
> {code}
> Then I use parquet-tools from [https://formulae.brew.sh/formula/parquet-tools] to check the metadata of parquet file via this command
> parquet-tools meta /tmp/test.parquet
> The full meta is included in attached, here is only an extraction of list type column
> games: OPTIONAL F:1 
>  .list: REPEATED F:1 
>  ..item: OPTIONAL F:2 
>  ...name: OPTIONAL BINARY L:STRING R:1 D:4
>  ...version: OPTIONAL BINARY L:STRING R:1 D:4
> as can be seen, under list, it is single field named _item_
> I think this should be made to be name _element_ to conform with Apache Parquet specification.



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