Prepend "-- " to default query_comment

dbt/adapters/athena/__init__.py

@@ -1,6 +1,7 @@
 from dbt.adapters.athena.connections import AthenaConnectionManager
 from dbt.adapters.athena.connections import AthenaCredentials
 from dbt.adapters.athena.impl import AthenaAdapter
+import dbt.adapters.athena.query_headers
 
 from dbt.adapters.base import AdapterPlugin
 from dbt.include import athena

dbt/adapters/athena/query_headers.py

@@ -0,0 +1,27 @@
+import dbt.adapters.base.query_headers
+
+class _QueryComment(dbt.adapters.base.query_headers._QueryComment):
+    """
+    Athena DDL does not always respect /* ... */ block quotations. 
+    This function is the same as _QueryComment.add except that 
+    a leading "-- " is prepended to the query_comment and any newlines
+    in the query_comment are replaced with " ". This allows the default
+    query_comment to be added to `create external table` statements.
+    """
+    def add(self, sql: str) -> str:
+        if not self.query_comment:
+            return sql
+
+        if self.append:
+            # replace last ';' with '<comment>;'
+            sql = sql.rstrip()
+            if sql[-1] == ";":
+                sql = sql[:-1]
+                return "{}\n-- /* {} */;".format(sql, self.query_comment.strip().replace("\n", " "))
+
+            return "{}\n-- /* {} */".format(sql, self.query_comment.strip().replace("\n", " "))
+
+        return "-- /* {} */\n{}".format(self.query_comment.strip().replace("\n", " "), sql)
+
+
+dbt.adapters.base.query_headers._QueryComment = _QueryComment