HIVE-21159 lands, enable HiveConf.MERGE_SPLIT_UPDATE and run these tests.
mvn test -Dtest=TestMiniLlapLocalCliDriver -Dqfile=insert_into_default_keyword.q
Merge is rewritten as a multi-insert. When Update clause has DEFAULT, it's not properly replaced with a value in the muli-insert - it's treated as a literal
See LOG.info("Going to reparse <" + originalQuery + "> as \n<" + rewrittenQueryStr.toString() + ">"); in hive.log
MergeSemanticAnalyzer.replaceDefaultKeywordForMerge() is only called in handleInsert but not handleUpdate(). Why does issue only show up with MERGE_SPLIT_UPDATE?
Once this is fixed, HiveConf.MERGE_SPLIT_UPDATE should be true by default