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From "Mariano, Laura J." <lmari...@draper.com>
Subject How to set output file size for parquet to csv conversions?
Date Tue, 15 Nov 2016 16:44:12 GMT
Hello all,

I have a large database of Parquet files that I need to convert to csv so they can be read
into Matlab. (Unless someone knows how to do this automatically without an intermediate step?).
I am using CTAS to create csv files from a directory of Parquet files, which works fine when
the total size of the Parquet files is smallish (~= 800MB).  In this case, CTAS will automatically
generate about a few csv files, ~200 - 300MB each, which are easily digestible by Matlab.

However, I have a dataset consisting of 34 Parquet files, totaling 18GB. When I run CTAS on
this to create the csv files using default parameters, it automatically generates 12 csv files,
>2GB each. This is approaching the upper limit of what Matlab can handle, so I am wondering
if there are any parameters I can set that will limit the size of the individual csv files
that are automatically created by the CTAS process. i.e. is there a parameter equivalent to
the store.parquet.block-size parameter for creating text files?

I am using Drill in embedded mode on a desktop.


Laura Mariano
Senior Member of the Technical Staff
(617) 258-2331

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