Man Linux: Main Page and Category List


       SET  CONSTRAINTS  -  set  constraint  checking  modes  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). 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  foreign key constraints are affected by this setting.
       Check and unique constraints are  always  effectively  not  deferrable.
       Triggers   that  are  declared  as  ‘‘constraint  triggers’’  are  also


       This command only alters the behavior of constraints within the current
       transaction. Thus, if you execute this command outside of a transaction
       block (BEGIN/COMMIT pair), it will not appear to have any effect.


       This command complies with the behavior defined in  the  SQL  standard,
       except  for  the  limitation  that,  in  PostgreSQL, it only applies to
       foreign-key constraints.