Steve Rogerson <steve.pg@xxxxxxxxxxxxxxxxx> writes: > On 05/01/16 19:47, Tom Lane wrote: >> That's operating as designed. A unique constraint needs an index, >> but not vice versa. > I can see that might be plausible , hence the question but as a "unique index" > imposes as constraint they seem equivalent. What's the functional difference > between the two situations? There is none so far as uniqueness-enforcement is concerned, because the index is the same either way, and that's what enforces it. The main reason we don't automatically create a constraint for every unique index is that not all index declarations can be represented by SQL-standard constraints. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
