On Thu, Dec 15, 2011 at 6:00 AM, Craig Ringer <ringerc@xxxxxxxxxxxxx> wrote: > On 12/15/2011 03:53 PM, Alban Hertroys wrote: >> >> Correct, but... >> That's not a particularly useful index to create. That index just contains >> values of true where the associated column equals true - you're storing the >> same information twice. > > It could be very handy if you have an extremely high selectivity index (say > 1:1000 or more) where you want to keep the index tiny, fast, and very quick > to scan. > > I guess ideally Pg would be able to deduce that the index value is always > the same and just store a page list rather than a b-tree, but it's a bit of > a tiny use case. The partial index is definitely a lot smaller. BTW, this table (RecipeMetadata) will only ever be used in a join. I will never query it directly. But I'll query Recipes and join in RecipeMetadata. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
