PostgreSQL: default constraint names

The standard names for indexes in PostgreSQL are:

{tablename}_{columnname(s)}_{suffix}

where the suffix is one of the following:

• pkey for a Primary Key constraint
• key for a Unique constraint
• excl for an Exclusion constraint
• idx for any other kind of index
• fkey for a Foreign key
• check for a Check constraint

Standard suffix for sequences is

• seq for all sequences

Proof of your UNIQUE-constraint:

NOTICE: CREATE TABLE / UNIQUE will
create implicit index
“example_a_b_key” for table “example”