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https://issues.apache.org/jira/browse/DRILL-7291?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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benj updated DRILL-7291:
------------------------
Component/s: Documentation
> parquet with compression gzip doesn't work well
> -----------------------------------------------
>
> Key: DRILL-7291
> URL: https://issues.apache.org/jira/browse/DRILL-7291
> Project: Apache Drill
> Issue Type: Bug
> Components: Documentation, Storage - Parquet
> Affects Versions: 1.15.0, 1.16.0
> Reporter: benj
> Priority: Major
> Attachments: 0_0_0.parquet, short_no_binary_quote.csvh,
> sqlline_error.log
>
>
> Create a parquet with compression=gzip produce bad result.
> Example:
> * input: file_pqt (compression=none)
> {code:java}
> ALTER SESSION SET `store.format`='parquet';
> ALTER SESSION SET `store.parquet.compression` = 'snappy';
> CREATE TABLE ....`file_snappy_pqt`
> AS(SELECT * FROM ....`file_pqt`);
> ALTER SESSION SET `store.parquet.compression` = 'gzip';
> CREATE TABLE ....`file_gzip_pqt`
> AS(SELECT * FROM ....`file_pqt`);{code}
> Then compare the content of the different parquet files:
> {code:java}
> ALTER SESSION SET `store.parquet.use_new_reader` = true;
> SELECT COUNT(*) FROM ....`file_pqt`; => 15728036
> SELECT COUNT(*) FROM ....`file_snappy_pqt`; => 15728036
> SELECT COUNT(*) FROM ....`file_gzip_pqt`; => 15728036
> => OK
> SELECT COUNT(*) FROM ....`file_pqt` WHERE `Code` = ''; => 0
> SELECT COUNT(*) FROM ....`file_snappy_pqt` WHERE `Code` = ''; => 0
> SELECT COUNT(*) FROM ....`file_gzip_pqt` WHERE `Code` = ''; => 14744966
> => NOK
> SELECT COUNT(*) FROM ....`file_pqt` WHERE `Code2` = ''; => 0
> SELECT COUNT(*) FROM ....`file_snappy_pqt` WHERE `Code2` = ''; => 0
> SELECT COUNT(*) FROM ....`file_gzip_pqt` WHERE `Code2` = ''; => 14744921
> => NOK{code}
> _(There is no NULL value in these files.)_
> _(With exec.storage.enable_v3_text_reader=true it gives same results)_
> So If the parquet file contains the right number of rows, the values in the
> different columns are not identical.
> Some "random" values of the _gzip parquet_ are reduce to empty string
> I think the problem is from the reader and not the writer because:
> {code:java}
> SELECT COUNT(*) FROM ....`file_pqt` WHERE `CRC32` = 'B33D600C'; => 2
> SELECT COUNT(*) FROM ....`file_gzip_pqt` WHERE `CRC32` = 'B33D600C'; => 0
> {code}
> but
> {code:java}
> hadoop jar parquet-tools-1.10.0.jar cat file_gzip_pqt/1_0_0.parquet | grep -c
> "B33D600C"
> 2019-06-12 11:45:23,738 INFO hadoop.InternalParquetRecordReader: RecordReader
> initialized will read a total of 3597092 records.
> 2019-06-12 11:45:23,739 INFO hadoop.InternalParquetRecordReader: at row 0.
> reading next block
> 2019-06-12 11:45:23,804 INFO zlib.ZlibFactory: Successfully loaded &
> initialized native-zlib library
> 2019-06-12 11:45:23,805 INFO compress.CodecPool: Got brand-new decompressor
> [.gz]
> 2019-06-12 11:45:23,815 INFO hadoop.InternalParquetRecordReader: block read
> in memory in 76 ms. row count = 3597092
> 2
> {code}
> So the values are well present in the _Apache Parquet_ file but can't be
> exploited via _Apache Drill_.
> In attachment an extract (the original file is 2.2 Go) which produce the same
> behaviour.
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