A common scenario when the table is partitioned on 'ds' column which is of type 'string' of a certain format 'yyyy-mm-dd'
However, if the user forgets to add quotes while specifying the query:
select ... from T where ds = 2009-02-02
2009-02-02 is a valid integer expression. So, partition pruning makes all partitions unknown, since 2009-02-02 to double conversion is null.
If all partitions are unknown, in strict mode, we should thrown an error