pg_constraint

The catalog pg_constraint stores check, not-null, primary key, unique, foreign key, and exclusion constraints on tables.

Reading PG 18current·documented in 24 of 24 versions, 7.4 to 20

7.4 8.0 8.1 8.2 8.3 8.4 9.0 9.1 9.2 9.3 9.4 9.5 9.6 10 11 12 13 14 15 16 17 18 19 20

Kind: System catalogs
Columns in this snapshot: 28
Definition source: English manual
Metadata snapshot: 18.6

Columns 28

As listed in the PostgreSQL 18 manual.

Column	Type	Description / reference
`oid`	`oid`NOT NULL	Row identifier
`conname`	`name`NOT NULL	Constraint name (not necessarily unique!)
`connamespace`	`oid`NOT NULL	The OID of the namespace that contains this constraint pg_namespace.oid
`contype`	`char`NOT NULL	c = check constraint, f = foreign key constraint, n = not-null constraint, p = primary key constraint, u = unique constraint, t = constraint trigger, x = exclusion constraint
`condeferrable`	`bool`NOT NULL	Is the constraint deferrable?
`condeferred`	`bool`NOT NULL	Is the constraint deferred by default?
`conenforced`	`bool`NOT NULL	Is the constraint enforced?
`convalidated`	`bool`NOT NULL	Has the constraint been validated?
`conrelid`	`oid`NOT NULL	The table this constraint is on; zero if not a table constraint pg_class.oid
`contypid`	`oid`NOT NULL	The domain this constraint is on; zero if not a domain constraint pg_type.oid
`conindid`	`oid`NOT NULL	The index supporting this constraint, if it's a unique, primary key, foreign key, or exclusion constraint; else zero pg_class.oid
`conparentid`	`oid`NOT NULL	The corresponding constraint of the parent partitioned table, if this is a constraint on a partition; else zero pg_constraint.oid
`confrelid`	`oid`NOT NULL	If a foreign key, the referenced table; else zero pg_class.oid
`confupdtype`	`char`NOT NULL	Foreign key update action code: a = no action, r = restrict, c = cascade, n = set null, d = set default
`confdeltype`	`char`NOT NULL	Foreign key deletion action code: a = no action, r = restrict, c = cascade, n = set null, d = set default
`confmatchtype`	`char`NOT NULL	Foreign key match type: f = full, p = partial, s = simple
`conislocal`	`bool`NOT NULL	This constraint is defined locally for the relation. Note that a constraint can be locally defined and inherited simultaneously.
`coninhcount`	`int2`NOT NULL	The number of direct inheritance ancestors this constraint has. A constraint with a nonzero number of ancestors cannot be dropped nor renamed.
`connoinherit`	`bool`NOT NULL	This constraint is defined locally for the relation. It is a non-inheritable constraint.
`conperiod`	`bool`NOT NULL	This constraint is defined with WITHOUT OVERLAPS (for primary keys and unique constraints) or PERIOD (for foreign keys).
`conkey`	`int2[]`	If a table constraint (including foreign keys, but not constraint triggers), list of the constrained columns pg_attribute.attnum
`confkey`	`int2[]`	If a foreign key, list of the referenced columns pg_attribute.attnum
`conpfeqop`	`oid[]`	If a foreign key, list of the equality operators for PK = FK comparisons pg_operator.oid
`conppeqop`	`oid[]`	If a foreign key, list of the equality operators for PK = PK comparisons pg_operator.oid
`conffeqop`	`oid[]`	If a foreign key, list of the equality operators for FK = FK comparisons pg_operator.oid
`confdelsetcols`	`int2[]`	If a foreign key with a SET NULL or SET DEFAULT delete action, the columns that will be updated. If null, all of the referencing columns will be updated. pg_attribute.attnum
`conexclop`	`oid[]`	If an exclusion constraint or WITHOUT OVERLAPS primary key/unique constraint, list of the per-column exclusion operators. pg_operator.oid
`conbin`	`pg_node_tree`	If a check constraint, an internal representation of the expression. (It's recommended to use pg_get_constraintdef() to extract the definition of a check constraint.)