Werner, it may be too long ago for you to answer my question, but

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was this a "simple":

ALTER TABLE tablename_of_mutillink MODIFY linkid INTEGER;
ALTER TABLE tablename_of_mutillink MODIFY nodeid INTEGER;

followed by a call to self.create_multilink_table_indexes(spec, ml)
or maybe just a reindex for the l_idx tables at the mysql level?
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-- rouilj