Unable to add exclude constraint to table

Question

I'm unable to create an excludes index with this schema.

create table foo_bar(
    foo_id text primary key,
    bar char(3) not null,
    created_at timestamptz not null default current_timestamp,
    system_period tstzrange not null default tstzrange(current_timestamp, null),
    exclude using gist (system_period with &&)
);

create table foo_bar_history(like foo_bar);

alter table foo_bar_history add constraint exclude using gist (system_period with &&);

The final alter table line here fails with

SQL Error [42601]: ERROR: syntax error at or near "using"

I've double checked the docs, but I really can't see what I'm doing wrong here.

PostgreSQL 9.6.9 on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 7.2.0-8ubuntu3.2) 7.2.0, 64-bit

Answer 1

You either have to specify the constraint name after CONSTRAINT or omit that keyword altogether so that PostgreSQL picks a name itself.