Parquet StringType column readable as plain-text despite being Gzipped

[Sung Hwan Chung <co...@cs.stanford.edu>]

Hello,

We are using the default compression codec for Parquet when we store our
dataframes. The dataframe has a StringType column whose values can be upto
several MBs large.

The funny thing is that once it's stored, we can browse the file content
with a plain text editor and see large portions of the string contents
unencrypted.

If we use the parquet-tool to browse the metadata, it says the column is
GZIP and the compression ratio is 2.6x, but that just doesn't seem right.

Anybody know what's going on?