1SET CONSTRAINTS(7) SQL Commands SET CONSTRAINTS(7)
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6 SET CONSTRAINTS - set constraint checking modes for the current trans‐
7 action
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11 SET CONSTRAINTS { ALL | name [, ...] } { DEFERRED | IMMEDIATE }
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15 SET CONSTRAINTS sets the behavior of constraint checking within the
16 current transaction. IMMEDIATE constraints are checked at the end of
17 each statement. DEFERRED constraints are not checked until transaction
18 commit. Each constraint has its own IMMEDIATE or DEFERRED mode.
19 Upon creation, a constraint is given one of three characteristics:
21 DEFERRABLE INITIALLY DEFERRED, DEFERRABLE INITIALLY IMMEDIATE, or NOT
22 DEFERRABLE. The third class is always IMMEDIATE and is not affected by
23 the SET CONSTRAINTS command. The first two classes start every transac‐
24 tion in the indicated mode, but their behavior can be changed within a
25 transaction by SET CONSTRAINTS.
26 SET CONSTRAINTS with a list of constraint names changes the mode of
28 just those constraints (which must all be deferrable). The current
29 schema search path is used to find the first matching name if no schema
30 name is specified. SET CONSTRAINTS ALL changes the mode of all
31 deferrable constraints.
32 When SET CONSTRAINTS changes the mode of a constraint from DEFERRED to
34 IMMEDIATE, the new mode takes effect retroactively: any outstanding
35 data modifications that would have been checked at the end of the
36 transaction are instead checked during the execution of the SET CON‐
37 STRAINTS command. If any such constraint is violated, the SET CON‐
38 STRAINTS fails (and does not change the constraint mode). Thus, SET
39 CONSTRAINTS can be used to force checking of constraints to occur at a
40 specific point in a transaction.
41 Currently, only foreign key constraints are affected by this setting.
43 Check and unique constraints are always effectively not deferrable.
44 Triggers that are declared as ``constraint triggers'' are also
45 affected.
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48 This command only alters the behavior of constraints within the current
49 transaction. Thus, if you execute this command outside of a transaction
50 block (BEGIN/COMMIT pair), it will not appear to have any effect.
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53 This command complies with the behavior defined in the SQL standard,
54 except for the limitation that, in PostgreSQL, it only applies to for‐
55 eign-key constraints.
56SQL - Language Statements 2011-09-22 SET CONSTRAINTS(7)