Fix parallel pg_restore to handle comments on POST_DATA items correctly.

The previous coding would try to process all SECTION_NONE items in the
initial sequential-restore pass, which failed if they were dependencies of
not-yet-restored items.  Fix by postponing such items into the parallel
processing pass once we have skipped any non-PRE_DATA item.

Back-patch into 9.0; the original parallel-restore coding in 8.4 did not
have this bug, so no need to change it.

Report and diagnosis by Arnd Hannemann.

diff --git a/src/bin/pg_dump/pg_backup_archiver.c b/src/bin/pg_dump/pg_backup_archiver.c
index 480264e911c7b5f4a7673a9f85f9d749c755c3f7..ff722db3c67c84cb731e77df82a26c302f833970 100644 (file)
--- a/src/bin/pg_dump/pg_backup_archiver.c
+++ b/src/bin/pg_dump/pg_backup_archiver.c
@@ -3218,12 +3218,12 @@ dumpTimestamp(ArchiveHandle *AH, const char *msg, time_t tim)
  * Main engine for parallel restore.
  *
  * Work is done in three phases.
- * First we process tocEntries until we come to one that is marked
- * SECTION_DATA or SECTION_POST_DATA, in a single connection, just as for a
- * standard restore.  Second we process the remaining non-ACL steps in
- * parallel worker children (threads on Windows, processes on Unix), each of
- * which connects separately to the database.  Finally we process all the ACL
- * entries in a single connection (that happens back in RestoreArchive).
+ * First we process all SECTION_PRE_DATA tocEntries, in a single connection,
+ * just as for a standard restore.  Second we process the remaining non-ACL
+ * steps in parallel worker children (threads on Windows, processes on Unix),
+ * each of which connects separately to the database.  Finally we process all
+ * the ACL entries in a single connection (that happens back in
+ * RestoreArchive).
  */
 static void
 restore_toc_entries_parallel(ArchiveHandle *AH)
@@ -3233,6 +3233,7 @@ restore_toc_entries_parallel(ArchiveHandle *AH)
    ParallelSlot *slots;
    int         work_status;
    int         next_slot;
+   bool        skipped_some;
    TocEntry    pending_list;
    TocEntry    ready_list;
    TocEntry   *next_work_item;
@@ -3262,12 +3263,31 @@ restore_toc_entries_parallel(ArchiveHandle *AH)
     * showing all the dependencies of SECTION_PRE_DATA items, so we do not
     * risk trying to process them out-of-order.
     */
+   skipped_some = false;
    for (next_work_item = AH->toc->next; next_work_item != AH->toc; next_work_item = next_work_item->next)
    {
-       /* Non-PRE_DATA items are just ignored for now */
-       if (next_work_item->section == SECTION_DATA ||
-           next_work_item->section == SECTION_POST_DATA)
-           continue;
+       /* NB: process-or-continue logic must be the inverse of loop below */
+       if (next_work_item->section != SECTION_PRE_DATA)
+       {
+           /* DATA and POST_DATA items are just ignored for now */
+           if (next_work_item->section == SECTION_DATA ||
+               next_work_item->section == SECTION_POST_DATA)
+           {
+               skipped_some = true;
+               continue;
+           }
+           else
+           {
+               /*
+                * SECTION_NONE items, such as comments, can be processed now
+                * if we are still in the PRE_DATA part of the archive.  Once
+                * we've skipped any items, we have to consider whether the
+                * comment's dependencies are satisfied, so skip it for now.
+                */
+               if (skipped_some)
+                   continue;
+           }
+       }
 
        ahlog(AH, 1, "processing item %d %s %s\n",
              next_work_item->dumpId,
@@ -3310,17 +3330,32 @@ restore_toc_entries_parallel(ArchiveHandle *AH)
     */
    par_list_header_init(&pending_list);
    par_list_header_init(&ready_list);
+   skipped_some = false;
    for (next_work_item = AH->toc->next; next_work_item != AH->toc; next_work_item = next_work_item->next)
    {
-       /* All PRE_DATA items were dealt with above */
+       /* NB: process-or-continue logic must be the inverse of loop above */
+       if (next_work_item->section == SECTION_PRE_DATA)
+       {
+           /* All PRE_DATA items were dealt with above */
+           continue;
+       }
        if (next_work_item->section == SECTION_DATA ||
            next_work_item->section == SECTION_POST_DATA)
        {
-           if (next_work_item->depCount > 0)
-               par_list_append(&pending_list, next_work_item);
-           else
-               par_list_append(&ready_list, next_work_item);
+           /* set this flag at same point that previous loop did */
+           skipped_some = true;
        }
+       else
+       {
+           /* SECTION_NONE items must be processed if previous loop didn't */
+           if (!skipped_some)
+               continue;
+       }
+
+       if (next_work_item->depCount > 0)
+           par_list_append(&pending_list, next_work_item);
+       else
+           par_list_append(&ready_list, next_work_item);
    }
 
    /*