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SET CONSTRAINTS(7)	PostgreSQL 9.6.20 Documentation	    SET	CONSTRAINTS(7)

       SET_CONSTRAINTS - set constraint	check timing for the current

       SET CONSTRAINTS { ALL | name [, ...] } {	DEFERRED | IMMEDIATE }

       SET CONSTRAINTS sets the	behavior of constraint checking	within the
       current transaction.  IMMEDIATE constraints are checked at the end of
       each statement.	DEFERRED constraints are not checked until transaction
       commit. Each constraint has its own IMMEDIATE or	DEFERRED mode.

       Upon creation, a	constraint is given one	of three characteristics:
       DEFERRABLE. The third class is always IMMEDIATE and is not affected by
       the SET CONSTRAINTS command. The	first two classes start	every
       transaction in the indicated mode, but their behavior can be changed
       within a	transaction by SET CONSTRAINTS.

       SET CONSTRAINTS with a list of constraint names changes the mode	of
       just those constraints (which must all be deferrable). Each constraint
       name can	be schema-qualified. The current schema	search path is used to
       find the	first matching name if no schema name is specified.  SET
       CONSTRAINTS ALL changes the mode	of all deferrable constraints.

       When SET	CONSTRAINTS changes the	mode of	a constraint from DEFERRED to
       IMMEDIATE, the new mode takes effect retroactively: any outstanding
       data modifications that would have been checked at the end of the
       transaction are instead checked during the execution of the SET
       CONSTRAINTS command. If any such	constraint is violated,	the SET
       CONSTRAINTS fails (and does not change the constraint mode). Thus, SET
       CONSTRAINTS can be used to force	checking of constraints	to occur at a
       specific	point in a transaction.

       Currently, only UNIQUE, PRIMARY KEY, REFERENCES (foreign	key), and
       EXCLUDE constraints are affected	by this	setting.  NOT NULL and CHECK
       constraints are always checked immediately when a row is	inserted or
       modified	(not at	the end	of the statement). Uniqueness and exclusion
       constraints that	have not been declared DEFERRABLE are also checked

       The firing of triggers that are declared	as "constraint triggers" is
       also controlled by this setting -- they fire at the same	time that the
       associated constraint should be checked.

       Because PostgreSQL does not require constraint names to be unique
       within a	schema (but only per-table), it	is possible that there is more
       than one	match for a specified constraint name. In this case SET
       CONSTRAINTS will	act on all matches. For	a non-schema-qualified name,
       once a match or matches have been found in some schema in the search
       path, schemas appearing later in	the path are not searched.

       This command only alters	the behavior of	constraints within the current
       transaction. Issuing this outside of a transaction block	emits a
       warning and otherwise has no effect.

       This command complies with the behavior defined in the SQL standard,
       except for the limitation that, in PostgreSQL, it does not apply	to NOT
       NULL and	CHECK constraints. Also, PostgreSQL checks non-deferrable
       uniqueness constraints immediately, not at end of statement as the
       standard	would suggest.

PostgreSQL 9.6.20		     2020		    SET	CONSTRAINTS(7)


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