Investigate compression of parquet exports

[manuelwedler]

It was reported on Matrix that our parquet exports are not compressed:

I just executed parquet meta code_0_100000.parquet and from the output it looks like that those parquet files support compression.. but it looks like those are not compressed ones .. e.g.

Row group 9:  count: 10000  8,246 kB records  start: 781314461  total(compressed): 80,530 MB total(uncompressed):80,530 MB

just compressed with bz2 to get a feeling how much compression could help

-rw-r--r--@ 1 alex  staff   826M Sep 30 15:10 code_0_100000.parquet
-rw-r--r--@ 1 alex  staff   165M Sep 30 20:24 code_0_100000.parquet.bz2

We should check why our parquet exports are not compressed and how we can make them compressed.