Re: operator exclusion constraints

Awhile back I wrote:
> * I'm not too satisfied with the behavior of psql's \d:

> regression=# create table foo (f1 int primary key using index tablespace ts1,
> regression(# f2 int, EXCLUDE USING btree (f2 WITH =) using index tablespace ts1,
> regression(# f3 int, EXCLUDE USING btree (f3 WITH =) DEFERRABLE INITIALLY DEFERRED);
> NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "foo_pkey" for table "foo"
> NOTICE: CREATE TABLE / EXCLUDE will create implicit index "foo_f2_exclusion" for table "foo"
> NOTICE: CREATE TABLE / EXCLUDE will create implicit index "foo_f3_exclusion" for table "foo"
> CREATE TABLE
> regression=# \d foo
> Table "public.foo"
> Column | Type | Modifiers
> --------+---------+-----------
> f1 | integer | not null
> f2 | integer |
> f3 | integer |
> Indexes:
> "foo_pkey" PRIMARY KEY, btree (f1), tablespace "ts1"
> "foo_f2_exclusion" btree (f2), tablespace "ts1"
> "foo_f3_exclusion" btree (f3) DEFERRABLE INITIALLY DEFERRED
> Exclusion constraints:
> "foo_f2_exclusion" EXCLUDE USING btree (f2 WITH =)
> "foo_f3_exclusion" EXCLUDE USING btree (f3 WITH =) DEFERRABLE INITIALLY DEFERRED

> regression=#

> This might have been defensible back when the idea was to keep constraints
> decoupled from indexes, but now it just looks bizarre. We should either
> get rid of the "Exclusion constraints:" display and attach the info to
> the index entries, or hide indexes that are attached to exclusion
> constraints. I lean to the former on the grounds of the precedent for
> unique/pkey indexes --- which is not totally arbitrary, since an index
> is usable as a query index regardless of its function as a constraint.
> It's probably a debatable point though.

Attached is a patch against HEAD that folds exclusion constraints into
\d's regular indexes list. With this, the above example produces

Table "public.foo"
Column | Type | Modifiers
--------+---------+-----------
f1 | integer | not null
f2 | integer |
f3 | integer |
Indexes:
"foo_pkey" PRIMARY KEY, btree (f1), tablespace "ts1"
"foo_f2_exclusion" EXCLUDE USING btree (f2 WITH =), tablespace "ts1"
"foo_f3_exclusion" EXCLUDE USING btree (f3 WITH =) DEFERRABLE INITIALLY DEFERRED

Any objections?

regards, tom lane