Thanks everyone for your feedback so far. I've done a bit more digging: MySQL in MBytes (about 350 million rows): index_user_event_on_what_category_id_created_at_latlng | 22806.00 index_user_event_for_reporting | 18211.00 index_user_event_on_created_at | 9519.00 index_user_event_on_user_id | 6884.00 index_user_event_on_poi_id | 4891.00 index_user_event_on_deal_id | 3979.00 Postgres (about 250 million rows): index_user_event_on_what_category_id_created_at_latlng | 25 GB index_user_event_for_reporting | 19 GB index_user_event_on_created_at | 7445 MB index_user_event_on_user_id | 7274 MB index_user_event_on_deal_id | 7132 MB index_user_event_on_poi_id | 7099 MB So, the index is a bit bigger, plus there is also the PKEY index which increases disk usage by another whole index. Keep in mind in the above, MySQL has about 40% more data. With some indexes, it looks like MySQL might not be adding all data to the index (e.g. ignoring NULL values). Does MySQL ignore null values in an index? Can we get the same behaviour in Postgres to minimise usage? What would be the recommendation here? For the composite indexes, if any value is null, we are also less interested in it, so it could be ignored from the index. Thanks, Samuel -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
