I use the NebulaGrpah version 3.4.1.
upsert edge on friend "14"->"15"@31 set `descr`=SPLIT(descr,",")+",1"
The above statement with the prompt "Storage Error: Invalid data, may be wrong value type." indicates that there is an issue with the data being updated.
The requirement is to modify the "descr" field by using the split function to extract the first element. It is unclear whether the upsert statement supports the split function.
