I created a table with two columns: an id SERIAL (primary key) and a text (not null), and then added a unique index on the text field. Then I ran the following query (with a huge work_mem - 20GB):
insert into tableA (text_field) select distinct other_text_field from some_huge_set_of_tables After 36 hours it had only written 3 GB (determined by looking at what files it was writing to). I started over with a TRUNCATE, and then removed the index and tried again. This time it took 3807270.780 ms (a bit over an hour). Total number of records: approx 227 million, comprising 16GB of storage. Why the huge discrepancy? -- Jon -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
