In case anyone else is facing this error when building a Raw Reflection for a Physical Dataset:
Table does not include column identified for incremental update of name
'$_dremio_$_update_$'.
It appears to occur when you have selected the option “Incremental update based on new files” for a Physical Dataset that uses partitioned Parquet files and you don’t select the partition fields “dir0” (and/or “dir1”, “dir2”, etc) for the Raw Reflection.
I resolved this by removing the Raw Reflection, modifying the Reflection Settings’ Refresh Method to use Full Update.
And then turning on the Raw Reflection with the dir0 fields, letting it build and then re-enabling the Incremental update option.