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https://issues.apache.org/jira/browse/IMPALA-2515?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Onur Tokat updated IMPALA-2515:
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Attachment: image-2020-02-07-11-33-27-944.png
> Impala is unable to read a Parquet decimal column if size is larger than
> needed
> -------------------------------------------------------------------------------
>
> Key: IMPALA-2515
> URL: https://issues.apache.org/jira/browse/IMPALA-2515
> Project: IMPALA
> Issue Type: Sub-task
> Components: Backend
> Affects Versions: Impala 2.3.0
> Reporter: Taras Bobrovytsky
> Assignee: Yongzhi Chen
> Priority: Minor
> Labels: ramp-up
> Attachments: image-2020-02-07-11-31-38-074.png,
> image-2020-02-07-11-31-43-641.png, image-2020-02-07-11-33-27-944.png
>
>
> Impala cannot read this:
> {code}
> {"name": "tmp_1",
> "type": "fixed",
> "size": 8,
> "logicalType": "decimal",
> "precision": 10,
> "scale": 5}
> {code}
> However, this can be read:
> {code}
> {"name": "tmp_1",
> "type": "fixed",
> "size": 5,
> "logicalType": "decimal",
> "precision": 10,
> "scale": 5}
> {code}
> Size must be precisely set to this, or Impala is unable to read the decimal
> column:
> {code}
> size = int(math.ceil((math.log(2, 10) + precision) / math.log(256, 10)))
> {code}
> There is nothing in the Parquet spec that says that Decimal columns must be
> sized precisely. Arguably it's a bug in the writer if it's doing it, because
> it's just wasting space.
> https://github.com/apache/parquet-format/blob/master/LogicalTypes.md#decimal
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