When there are constant values in select list and equi-join keys are text columns, it causes some errors due to schema mismatch.
Its cause of this bug is as follows:
- the number 1 results in a generated column name '?literal'.
- This name is used in both table1 and table2. Output schemas of table1 and table2 include ?literal
- The input schema of join has only three columns because ?literal is duplicated name.
So, its essential bug may be one of following:
- The constant value is evaluated twice. In other words, literal? occurs in both table1 and table2.
- Schema class does not allow the same column name.