Re: pg_restore dependencies - Mailing list pgsql-hackers

Tom Lane wrote:
> Andrew Dunstan <andrew@dunslane.net> writes:
>
>> What you're missing is that we need to compare the lockdeps of each item
>> (i.e. both the candidate item and the running item) with all the deps
>> (not just the lockdeps) of the other item. If neither item has any
>> lockdeps there will be no conflict. This will allow concurrent index
>> creation, since neither item will have any lockdeps. But it will prevent
>> us selecting a create index that conflicts with a running FK creation or
>> vice versa.
>>
>
> Oh, I see, you're using the deps as a proxy for the shared locks the
> operation will acquire.  Yeah, that might work.  Seems like it's nearly
> a one-liner fix, too.
>
>
>

Well, what I have in mind is a bit bigger, but not large. See attached
patch.

cheers

andrew
*** pg_backup_archiver.c    2009-04-10 00:09:57.000000000 -0400
--- pg_backup_archiver-fix.c    2009-04-10 19:22:07.000000000 -0400
***************
*** 3423,3433 ****
              if (slots[i].args == NULL)
                  continue;
              running_te = slots[i].args->te;
              for (j = 0; j < te->nLockDeps && !conflicts; j++)
              {
!                 for (k = 0; k < running_te->nLockDeps; k++)
                  {
!                     if (te->lockDeps[j] == running_te->lockDeps[k])
                      {
                          conflicts = true;
                          break;
--- 3423,3450 ----
              if (slots[i].args == NULL)
                  continue;
              running_te = slots[i].args->te;
+             /* does the candidate item require an exclusive lock that
+              * would block on or conflict with the running item?
+              */
              for (j = 0; j < te->nLockDeps && !conflicts; j++)
              {
!                 for (k = 0; k < running_te->nDeps; k++)
                  {
!                     if (te->lockDeps[j] == running_te->dependencies[k])
!                     {
!                         conflicts = true;
!                         break;
!                     }
!                 }
!             }
!             /* or does the running item hold an exclusive lock that
!              * would block or conflict with the candidate item?
!              */
!             for (j = 0; j < running_te->nLockDeps && !conflicts; j++)
!             {
!                 for (k = 0; k < te->nDeps; k++)
!                 {
!                     if (running_te->lockDeps[j] == te->dependencies[k])
                      {
                          conflicts = true;
                          break;