Yeah, I've no idea how it was that much slower but they were reasonably sized tables (x00M rows) with tens of columns and it was basically a full join on each column - probably would need an index on every column to make it sensible?
[edit: And with CDR mediation, it's not as simple as "do all the columns match exactly?" because some of them are going to be different in certain allowed ways which needs to be considered a match and also you need to be able to identify which rows differ in one column to say "these look the same but XYZ is different?" Which is probably why the query was horrendous.]
[edit: And with CDR mediation, it's not as simple as "do all the columns match exactly?" because some of them are going to be different in certain allowed ways which needs to be considered a match and also you need to be able to identify which rows differ in one column to say "these look the same but XYZ is different?" Which is probably why the query was horrendous.]