apply_constraints

[beckom4]

Hi,
Which lock does the function apply_constraints use on the table during its run? We're trying to figure out if we can use it to apply new constraints and indexes on existing partitioned tables.
Thanks!

[keithf4]

Going by the documentation, it looks like most constraints do take out an access exclusive lock on the table.

https://www.postgresql.org/docs/17/sql-altertable.html

Although most forms of ADD table_constraint require an ACCESS EXCLUSIVE lock, ADD FOREIGN KEY requires only a SHARE ROW 
EXCLUSIVE lock. Note that ADD FOREIGN KEY also acquires a SHARE ROW EXCLUSIVE lock on the referenced table, in addition to the 
lock on the table on which the constraint is declared.

Additional restrictions apply when unique or primary key constraints are added to partitioned tables; see 
[CREATE TABLE](https://www.postgresql.org/docs/17/sql-createtable.html). Also, foreign key constraints on partitioned tables may not be
 declared NOT VALID at present.