Re: [BUGS] BUG #14596: False primary/unique key constraint violations

rasmus@mindplay.dk writes:
> It looks like constraints are being checked row-by-row while the udpate is
> happening?

This is documented somewhere ... ah, here, in the COMPATIBILITY section of
the CREATE TABLE reference page:

  Non-deferred Uniqueness Constraints

  When a UNIQUE or PRIMARY KEY constraint is not deferrable, PostgreSQL
  checks for uniqueness immediately whenever a row is inserted or
  modified. The SQL standard says that uniqueness should be enforced only
  at the end of the statement; this makes a difference when, for example,
  a single command updates multiple key values. To obtain
  standard-compliant behavior, declare the constraint as DEFERRABLE but
  not deferred (i.e., INITIALLY IMMEDIATE). Be aware that this can be
  significantly slower than immediate uniqueness checking.


            regards, tom lane


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