1SET CONSTRAINTS(7)       PostgreSQL 12.6 Documentation      SET CONSTRAINTS(7)
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NAME

6       SET_CONSTRAINTS - set constraint check timing for the current
7       transaction
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SYNOPSIS

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

13       SET CONSTRAINTS sets the behavior of constraint checking within the
14       current transaction.  IMMEDIATE constraints are checked at the end of
15       each statement.  DEFERRED constraints are not checked until transaction
16       commit. Each constraint has its own IMMEDIATE or DEFERRED mode.
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18       Upon creation, a constraint is given one of three characteristics:
19       DEFERRABLE INITIALLY DEFERRED, DEFERRABLE INITIALLY IMMEDIATE, or NOT
20       DEFERRABLE. The third class is always IMMEDIATE and is not affected by
21       the SET CONSTRAINTS command. The first two classes start every
22       transaction in the indicated mode, but their behavior can be changed
23       within a transaction by SET CONSTRAINTS.
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25       SET CONSTRAINTS with a list of constraint names changes the mode of
26       just those constraints (which must all be deferrable). Each constraint
27       name can be schema-qualified. The current schema search path is used to
28       find the first matching name if no schema name is specified.  SET
29       CONSTRAINTS ALL changes the mode of all deferrable constraints.
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31       When SET CONSTRAINTS changes the mode of a constraint from DEFERRED to
32       IMMEDIATE, the new mode takes effect retroactively: any outstanding
33       data modifications that would have been checked at the end of the
34       transaction are instead checked during the execution of the SET
35       CONSTRAINTS command. If any such constraint is violated, the SET
36       CONSTRAINTS fails (and does not change the constraint mode). Thus, SET
37       CONSTRAINTS can be used to force checking of constraints to occur at a
38       specific point in a transaction.
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40       Currently, only UNIQUE, PRIMARY KEY, REFERENCES (foreign key), and
41       EXCLUDE constraints are affected by this setting.  NOT NULL and CHECK
42       constraints are always checked immediately when a row is inserted or
43       modified (not at the end of the statement). Uniqueness and exclusion
44       constraints that have not been declared DEFERRABLE are also checked
45       immediately.
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47       The firing of triggers that are declared as “constraint triggers” is
48       also controlled by this setting — they fire at the same time that the
49       associated constraint should be checked.
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NOTES

52       Because PostgreSQL does not require constraint names to be unique
53       within a schema (but only per-table), it is possible that there is more
54       than one match for a specified constraint name. In this case SET
55       CONSTRAINTS will act on all matches. For a non-schema-qualified name,
56       once a match or matches have been found in some schema in the search
57       path, schemas appearing later in the path are not searched.
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59       This command only alters the behavior of constraints within the current
60       transaction. Issuing this outside of a transaction block emits a
61       warning and otherwise has no effect.
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COMPATIBILITY

64       This command complies with the behavior defined in the SQL standard,
65       except for the limitation that, in PostgreSQL, it does not apply to NOT
66       NULL and CHECK constraints. Also, PostgreSQL checks non-deferrable
67       uniqueness constraints immediately, not at end of statement as the
68       standard would suggest.
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72PostgreSQL 12.6                      2021                   SET CONSTRAINTS(7)
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