Thanks Tom. Here's more info: What have you got work_mem set to?
40960 What's the actual number of groups
(target_page_id values)?
Approximately 40 million (I'll have a more precise number when the query finishes running ). Maybe this helps? crystal=> select null_frac, n_distinct, correlation from pg_stats where tablename = 'page_page_link' and attname = 'target_page_id'; null_frac | n_distinct | correlation -----------+------------+------------- 0 | 550017 | 0.240603 (1 row) Mason