Re: Dropping behavior for unique CONSTRAINTs

On 3/4/23 05:51, Peter J. Holzer wrote:
> On 2023-03-04 02:34:02 -0600, Ron wrote:
>> On 3/4/23 02:03, Peter J. Holzer wrote:
>> [snip]
>>> So your plan is to create a unique constraint (backed by a unique
>>> index) and then to drop the index and keep the constraint?
>>>
>>> That doesn't work. A unique constraint can't exist without a (unique)
>>> index. Think about it: With a unique constraint PostgreSQL needs to
>>> check for every insert whether the value already exists in the table.
>>> Without an index this would mean a full table scan.
>> I cut my teeth on an RDBMS which didn't automagically create a backing
>> index.  You had to do it yourself...
> Just curious: Which RDBMS was that?

Rdb/VMS (the DEC product for OpenVMS, which has been owned by Oracle for the
past 25 years).

> Speaking of foreign key constraints: Neither Oracle nor PostgreSQL
> automatically add an index on a foreign key. That bit me hard back in
> the day ...

Us too.  (Well, the developer, from before I arrived.)

--
Born in Arizona, moved to Babylonia.