schemas/py_functions.sql: _date(): Re-enabled now that exceptions thrown are properly handled. FormatException: Support raising parsable data_exceptions when provided with the value that was invalid. Date parsing mode: Return date as the value in FormatException so it can be filtered out automatically by column-based import.

sql_io.py: put_table(): is_function: Creating error handling wrapper function: Fixed bug where needed to cast NULL returned in error handler to appropriate type, because it's contained within a SELECT query which does not do implicit casts from type unknown

sql_gen.py: Cast: Support types which are Code objects

sql_io.py: func_wrapper_exception_handler(): Use new sql_gen.merge_not_null() to try to ensure that NULL values are not folded (which would cause the concatenated values not to match up with the concatenated column names). Note that this adds a dependency on the db object, which callers must now provide.

sql_gen.py: Added merge_not_null()

sql_gen.py: Added try_mk_not_null()

sql_gen.py: Renamed ArrayJoin to ArrayMerge to avoid confusion with Join (a SQL construct)

sql_io.py: put_table(): is_function: Creating error handling wrapper function: Set srcs on row_var so that the column type and nullability info of row_var's columns can be retrieved for use with sql_gen.ensure_not_null()

sql_gen.py: RowExcIgnore.to_str(): Compare self.row_var to global const row_var using == to allow caller to provide a copy of row_var with the underlying table set appropriately

sql_gen.py: underlying_table(): Support derived tables and row vars by obtaining the underlying table from the srcs