Hi Stefan! condition1 is like this: exists (select 1 from temp_assoc_counts tc where tc.xtrsrc_id = temp_associations.xtrsrc_id and tc.assoc_count = 1) condition 2 is like: kind is null I have also bumped in the same situation, when condition2 was like "kind = 2". But when "2" was replaced to a column name (with all values in this column were 2) - it worked fine. I.e. there is something wrong when constant appears in the condition. Traces can be seen in attachment.