If an scalar subquery is used with an equality predicate, it must return only one row/column to be valid. If this can not be guaranteed at parse time through a single row aggregate or limit clause, Impala fails the query like such.
Impala should allow these to run successfully by adding a run time assert in these cases if the SQ returns > 1 row when it should not.
This impacts TPC-DS query6, query54, query58.
|Add run time scalar subquery check for uncorrelated subqueries||Resolved|
|Add run time scalar subquery check for correlated subqueries||Open||Unassigned|