Column name ambiguous when defining exportable with join using same field name

Problem description:

I have two tables with the column 'machine_name', joined together. Ctools adds a condition on this key name, but without specifying the table. Here's the full error.

Exception thrown

PDOException: SQLSTATE[23000]: Integrity constraint violation: 1052 Column 'machine_name' in where clause is ambiguous: SELECT t__0.*, t__1.* FROM {base_table} t__0 INNER JOIN {joined_table} t__1 ON t__0.machine_name = t__1.machine_name WHERE (machine_name IN (:db_condition_placeholder_0)) ; Array ( [:db_condition_placeholder_0] => the_name ) in ctools_export_load_object() (line 462 of sites/all/modules/contrib/ctools/includes/export.inc).

Additional problem

The documentation talks about 'key in table', which is not used anywhere in the code. I believe this should be THE place to use it.

Proposed solution:

Prepend the column name in the WHERE clause with the table specified in 'key in table', or the table the export is defined in.