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