With the advent of qc_get_field_info, columns can now be matched.
However, there is still some undeterminism caused by the table
information not containing contextual information (exactly where
is the table used).
Further, suppose table X contains the column A and table Y contains
the column B, then given a statement like
SELECT a, b from X, Z;
we cannot know whether a is in X or Z, or b in X or Z, without being
aware of the schema, which we currently are not.
Consequently, as long as MaxScale is not aware of the schema, some
heuristics must be applied. For instance, if exactly one table is
referred to, then we can assume that columns that are not explicitly
qualified are from that table.
The rule tests are currently rather rudimentary and need to be
expanded.
c4999232ce