Not sure if this is an actual defect in the dse driver, but filing so that someone can investigate / verify / refute.
When I use riptano ccm to create and query an empty linestring in DSE5 (5.0-dev branch, synced around 6/6/2016), I get this reasonable result:
When I do the same thing for Polygon, I get the following result:
I'm puzzled that the embedded cassandra driver works for either type, since geospatial type handling is a feature of the dse driver. But taking that it works for linestring, I'd expect it to work for polygon, and thus suspect there is a defect here.
Ok, I just realized that "LINESTRING ()" is not valid WKT...or at least DSE craps out on that string if you try to insert a value with that text. So, either DSE's wkt parser is wrong, or the Python DSE driver is wrong in rendering an empty linestring as "LINESTRING ()".
Maybe I'm missing something here, but we have tests for this exact scenario. Located here
This is currently working on EAP7 I wonder if there wasn't some change on DSE.
The only difference being that we select the specific key we want rather then *.
bdp master presently has an old version of the DSE driver integrated. They're upgrading here: https://datastax.jira.com/browse/DSP-9572
I also confirmed that the type works using the current driver: