pg_constraint

The pg_constraint system catalog table stores check, primary key, unique, and foreign key constraints on tables. Column constraints are not treated specially. Every column constraint is equivalent to some table constraint. Not-null constraints are represented in the pg_attribute catalog table. Check constraints on domains are stored here, too.

Column Type References Description

Column	Type	References	Description
conname	name	—	Constraint name (not necessarily unique)
connamespace	oid	pg_namespace.oid	The OID of the namespace (schema) that contains this constraint
contype	char	—	`c` — check constraint. `f` — foreign key constraint. `p` — primary key constraint. `u` — unique constraint. `t` — constraint trigger.
condeferrable	boolean	—	Indicates whether the constraint is deferrable
condeferred	boolean	—	Indicates whether the constraint is deferred by default
convalidated	boolean	—	Indicates whether the constraint has been validated. Currently, can only be `false` for foreign keys
conrelid	oid	pg_class.oid	The table this constraint is on; `0` if not a table constraint
contypid	oid	pg_type.oid	The domain this constraint is on; `0` if not a domain constraint
conindid	oid	pg_class.oid	The index supporting this constraint, if it is a unique, primary key, or foreign key constraint; else `0`
confrelid	oid	pg_class.oid	If a foreign key, the referenced table; else `0`
confupdtype	char	—	Foreign key update action code
confdeltype	char	—	Foreign key deletion action code
confmatchtype	char	—	Foreign key match type
conislocal	boolean	—	This constraint is defined locally for the relation. Note that a constraint can be locally defined and inherited simultaneously
coninhcount	integer	—	The number of direct inheritance descendants this constraint has. A constraint with a nonzero number of descendants cannot be dropped nor renamed
connoinherit	boolean	—	Indicates if the constraint is local and cannot be inherited by child tables
conkey	int2[]	pg_attribute.attnum	If a table constraint, list of columns which the constraint constrains
confkey	int2[]	pg_attribute.attnum	If a foreign key, list of the referenced columns
conpfeqop	oid[]	pg_operator.oid	If a foreign key, list of the equality operators for PK = FK comparisons
conppeqop	oid[]	pg_operator.oid	If a foreign key, list of the equality operators for PK = PK comparisons
conffeqop	oid[]	pg_operator.oid	If a foreign key, list of the equality operators for FK = FK comparisons
conexclop	oid[]	pg_operator.oid	If an exclusion constraint, list of the per-column exclusion operators
conbin	text	—	If a check constraint, an internal representation of the expression
consrc	text	—	If a check constraint, a human-readable representation of the expression

conname

name

—

Constraint name (not necessarily unique)

connamespace

oid

pg_namespace.oid

The OID of the namespace (schema) that contains this constraint

contype

char

—

c — check constraint.
f — foreign key constraint.
p — primary key constraint.
u — unique constraint.
t — constraint trigger.

condeferrable

boolean

—

Indicates whether the constraint is deferrable

condeferred

boolean

—

Indicates whether the constraint is deferred by default

convalidated

boolean

—

Indicates whether the constraint has been validated. Currently, can only be false for foreign keys

conrelid

oid

pg_class.oid

The table this constraint is on; 0 if not a table constraint

contypid

oid

pg_type.oid

The domain this constraint is on; 0 if not a domain constraint

conindid

oid

pg_class.oid

The index supporting this constraint, if it is a unique, primary key, or foreign key constraint; else 0

confrelid

oid

pg_class.oid

If a foreign key, the referenced table; else 0

confupdtype

char

—

Foreign key update action code

confdeltype

char

—

Foreign key deletion action code

confmatchtype

char

—

Foreign key match type

conislocal

boolean

—

This constraint is defined locally for the relation. Note that a constraint can be locally defined and inherited simultaneously

coninhcount

integer

—

The number of direct inheritance descendants this constraint has. A constraint with a nonzero number of descendants cannot be dropped nor renamed

connoinherit

boolean

—

Indicates if the constraint is local and cannot be inherited by child tables

conkey

int2[]

pg_attribute.attnum

If a table constraint, list of columns which the constraint constrains

confkey

int2[]

pg_attribute.attnum

If a foreign key, list of the referenced columns

conpfeqop

oid[]

pg_operator.oid

If a foreign key, list of the equality operators for PK = FK comparisons

conppeqop

oid[]

pg_operator.oid

If a foreign key, list of the equality operators for PK = PK comparisons

conffeqop

oid[]

pg_operator.oid

If a foreign key, list of the equality operators for FK = FK comparisons

conexclop

oid[]

pg_operator.oid

If an exclusion constraint, list of the per-column exclusion operators

conbin

text

—

If a check constraint, an internal representation of the expression

consrc

text

—

If a check constraint, a human-readable representation of the expression

pg_compression

pg_conversion