I wrote:
> Barring objections or better ideas, I'll push forward with applying
> this patch and the dependency-fixup patch.
Applied and back-patched.
BTW, I had complained at the end of the pgsql-bugs thread about bug #6699
that it seemed like FK constraints would get prevented from being
restored in parallel fashion if they depended on a constraint-style
unique index, because the dependency for the FK constraint would
reference the index's dump ID, which is nowhere to be seen in the dump.
But in fact they are restored in parallel, and the reason is that
pg_restore silently ignores any references to unknown dump IDs (a hack
put in specifically because of the bogus dependency data, no doubt).
So that raises the opposite question: how come pg_restore doesn't fall
over from trying to create the FK constraint before the unique index it
depends on is created? And the answer to that is dumb luck, more or
less. The "locking dependencies" hack in pg_restore knows that creation
of an FK constraint requires exclusive lock on both tables, so it won't
try to restore the FK constraint before creation of the constraint-style
index is done. So getting the dependency information fixed is a
necessary prerequisite for any attempt to reduce the locking
requirements there.
regards, tom lane
