Carlos Alves <carlos.alves@xxxxxxxxxxxxxxx> writes: > I need some help to understand why a transaction wiht a row delete > aquire a AccessExclusiveLock and a row update a ExclusiveLock. UPDATE can use the weaker lock type if it's not modifying any column that is part of a unique index. This is to allow concurrency with foreign-key checks that might wish to grab a read-only (shared) lock on such a tuple. A DELETE, or an UPDATE that is modifying key columns, has to conflict with foreign-key checks. regards, tom lane
