pg_constraint - PolarDB - Alibaba Cloud Documentation Center

The catalog pg_constraint stores check, primary key, unique, foreign key, and exclusion 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, not here.User-defined constraint triggers (created with CREATE CONSTRAINT TRIGGER) also give rise to an entry in this table. Check constraints on domains are stored here, too.

Column	Type	Description
`oid`	`oid`	Row identifier.
`conname`	`name`	Constraint name (not necessarily unique!).
`connamespace`	`oid`	The OID of the namespace that contains this constraint.
`contype`	`char`	`c`= check constraint `f`= foreign key constraint `p`= primary key constraint `u`= unique constraint `t`= constraint trigger `x`= exclusion constraint
`condeferrable`	`bool`	Is the constraint deferrable?
`condeferred`	`bool`	Is the constraint deferred by default?
`convalidated`	`bool`	Has the constraint been validated? Currently, can be false only for foreign keys and CHECK constraints.
`conrelid`	`oid`	The table this constraint is on; zero if not a table constraint.
`contypid`	`oid`	The domain this constraint is on; zero if not a domain constraint.
`conindid`	`oid`	The index supporting this constraint, if it's a unique, primary key, foreign key, or exclusion constraint; else zero.
`conparentid`	`oid`	The corresponding constraint of the parent partitioned table, if this is a constraint on a partition; else zero.
`confrelid`	`oid`	If a foreign key, the referenced table; else zero.
`confupdtype`	`char`	Foreign key update action code: `a`: no action `r`: restrict `c`: cascade `n`: set null `d`: set default
`confdeltype`	`char`	Foreign key deletion action code: `a`: no action `r`: restrict `c`: cascade `n`: set null `d`: set default
`confmatchtype`	`char`	Foreign key match type: `f`: full `p`: partial `s` : simple
`conislocal`	`bool`	This constraint is defined locally for the relation. Note that a constraint can be locally defined and inherited simultaneously.
`coninhcount`	`int4`	The number of direct inheritance ancestors this constraint has. A constraint with a nonzero number of ancestors cannot be dropped nor renamed.
`connoinherit`	`bool`	This constraint is defined locally for the relation. It is a non-inheritable constraint.
`conkey`	`int2[]`	If a table constraint (including foreign keys, but not constraint triggers), list of the constrained columns.
`confkey`	`int2[]`	If a foreign key, list of the referenced columns.
`conpfeqop`	`oid[]`	If a foreign key, list of the equality operators for PK = FK comparisons.
`conppeqop`	`oid[]`	If a foreign key, list of the equality operators for PK = PK comparisons.
`conffeqop`	`oid[]`	If a foreign key, list of the equality operators for FK = FK comparisons.
`conexclop`	`oid[]`	If an exclusion constraint, list of the per-column exclusion operators.
`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.)

In the case of an exclusion constraint,conkey is only useful for constraint elements that are simple column references. For other cases, a zero appears in conkey and the associated index must be consulted to discover the expression that is constrained. (conkey thus has the same contents as pg_index.indkey for the index.)

Note

pg_class.relchecks needs to agree with the number of check-constraint entries found in this table for each relation.