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How can I acces data from an hdfs in parquet format

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André Horn
André Horn 2018-9-17
评论： Hatem Helal 2019-4-10
We have a large dataset stored in parquet files on an hadoop file system and would like to use a matlab datastore to analyse them. Unfortunately I couldn't find any reports, that anybody has done this yet.
Does mathworks provide a native way to access parquet data? Perhaps one can use the fileDatastore or a matlab custom datastore? Is there a template for that?

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Hitesh Kumar Dasika
Hitesh Kumar Dasika 2018-12-20
Mathworks has added support for Parquet files. it is available in the following link.
matlab-parquet
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Knut Voigtlaender
Knut Voigtlaender 2019-1-16
Indeed, I'm able to access parquet files hosted on a remote hadoop linux cluster from a local Windows PC Matlab.
For me it worked considering following steps:
1. I got a local Hadoop Windows installation according to
https://github.com/MuhammadBilalYar/Hadoop-On-Window/wiki/Step-by-step-Hadoop-2.8.0-installation-on-Window-10
2. log4j.properties must be copied from \hadoop-X.X.X\ect\hadoop\ to \matlab-parquet-master\Software\MATLAB\lib\jar\
3. The HADOOP_HOME environment variable should then point to the local hadoop home directory instead to Winutils.exe
4. The check for unix-style filename was removed in matlab-parquet-master\Software\MATLAB\+bigdata\+parquet\Reader.m
5. The OS-check must be removed from \matlab-parquet-master\Software\MATLAB\functions\parquetDatastore.m
or like proposed above it is possible to use directly \matlab-parquet-master\Software\MATLAB\+bigdata\+parquet\ParquetDatastore.m
After this steps I could initialize a Datastore via a remote hadoop url like
ds=bigdata.parquet.ParquetDatastore('hdfs://server:port/dir','IncludeSubfolders',true)
Hatem Helal
Hatem Helal 2019-4-10
R2019a adds support for working with parquet files, see this answer and let us know if you have any further feedback.

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更多回答（2 个）

Hatem Helal
Hatem Helal 2019-4-10
MATLAB R2019a adds support for reading and writing Apache Parquet files (doc). Here are the relevant release notes:
1. Import and export column-oriented data from Parquet files in MATLAB. Parquet is a columnar storage format that supports efficient compression and encoding schemes. To work with the Parquet file format, use these functions.
2. The write function now supports writing tall arrays to Parquet files. To write a tall array, set the FileType parameter to 'parquet', for example:
write('C:\myData',tX,'FileType','parquet')
3. Read a collection of Parquet files into MATLAB workspace using parquetDatastore.
For more information on the Parquet file format, see https://parquet.apache.org/.
Hitesh Kumar Dasika
Currently, there is no support to Apache Arrow and Parquet files in MATLAB.
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Hitesh Kumar Dasika
Hitesh Kumar Dasika 2018-9-24
Thank you for your feedback. We have raised this concern with our developers and they are actively looking at including this feature in our future releases. Unfortunately, there is no workaround in this case for now. Sorry for the trouble.
Hatem Helal
Hatem Helal 2019-4-10
R2019a adds support for working with parquet files, see this answer and let us know if you have any further feedback.

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