Snowflake write: escape backslash in CSV files

[turb]

Unsure it is the right way to do that — can't find how to properly configure escapes chars with kantan.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 61.28%. Comparing base (d5d20ad) to head (40c7611).

Files with missing lines	Patch %	Lines
...scala/com/spotify/scio/snowflake/SnowflakeIO.scala	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5551      +/-   ##
==========================================
- Coverage   61.29%   61.28%   -0.01%     
==========================================
  Files         314      314              
  Lines       11250    11250              
  Branches      793      776      -17     
==========================================
- Hits         6896     6895       -1     
- Misses       4354     4355       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[RustedBones]

If the data contains \, shouldn't it be better to set ESCAPE_UNENCLOSED_FIELD=NONE as explained here ?

[turb]

If the data contains , shouldn't it be better to set ESCAPE_UNENCLOSED_FIELD=NONE as explained here ?

I don't think it would work with data that may contains all between comma , backslash \ and simple quote ' — which is escaped by \'.

We found this because we have data with a string like something \ (or in Scala syntax "something \\") that encodes in CSV as 'something \'. Then the Snowflake parser interprets the quote as escaped.

With the fix it's now 'something \\' ("something \\\\" in scala syntax).

It may be managed by kantan (with kantan.csv.CsvConfiguration), but it seems only at the kantan.csv level, not kantan.codecs.

[turb]

FYI I also opened a PR in Apache Beam: apache/beam#33803

I think it's difficult to have something really clean, since Beam does half a CSV serialization: doing a naive fields.mkString("'", "','", "'"). So providing the other half (array of serialized fields) can only be a hack around that...