Fix logic to detect conflicts or blocks involving exclusive locks in parallel restore items.

If a currently running item needs an exclusive lock on any item that the candidate items needs
any sort of lock on, or vice versa, then the candidate item is not allowed to run now, and
must wait till later.

src/bin/pg_dump/pg_backup_archiver.c

@@ -15,7 +15,7 @@
  *
  *
  * IDENTIFICATION
- *		$PostgreSQL: pgsql/src/bin/pg_dump/pg_backup_archiver.c,v 1.169 2009/03/26 22:26:07 petere Exp $
+ *		$PostgreSQL: pgsql/src/bin/pg_dump/pg_backup_archiver.c,v 1.170 2009/04/12 21:02:44 adunstan Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -124,6 +124,7 @@ static parallel_restore_result parallel_restore(RestoreArgs *args);
 static void mark_work_done(ArchiveHandle *AH, thandle worker, int status,
 						   ParallelSlot *slots, int n_slots);
 static void fix_dependencies(ArchiveHandle *AH);
+static bool has_lock_conflicts(TocEntry *te1, TocEntry *te2);
 static void repoint_table_dependencies(ArchiveHandle *AH,
 									   DumpId tableId, DumpId tableDataId);
 static void identify_locking_dependencies(TocEntry *te,
@@ -3350,6 +3351,29 @@ get_next_slot(ParallelSlot *slots, int n_slots)
 	return NO_SLOT;
 }
 
+
+/*
+ * Check if te1 has an exclusive lock requirement for an item that te2 also
+ * requires, whether or not te2's requirement is for an exclusive lock.
+ */
+static bool
+has_lock_conflicts(TocEntry *te1, TocEntry *te2)
+{
+	int j,k;
+
+	for (j = 0; j < te1->nLockDeps; j++)
+	{
+		for (k = 0; k < te2->nDeps; k++)
+		{
+			if (te1->lockDeps[j] == te2->dependencies[k])
+				return true;
+		}
+	}
+	return false;
+}
+
+
+
 /*
  * Find the next work item (if any) that is capable of being run now.
  *
@@ -3373,7 +3397,7 @@ get_next_work_item(ArchiveHandle *AH, TocEntry **first_unprocessed,
 	bool      pref_non_data = false; /* or get from AH->ropt */
 	TocEntry *data_te = NULL;
 	TocEntry *te;
-	int       i,j,k;
+	int       i,k;
 
 	/*
 	 * Bogus heuristics for pref_non_data
@@ -3413,8 +3437,8 @@ get_next_work_item(ArchiveHandle *AH, TocEntry **first_unprocessed,
 
 		/*
 		 * Check to see if the item would need exclusive lock on something
-		 * that a currently running item also needs lock on.  If so, we
-		 * don't want to schedule them together.
+		 * that a currently running item also needs lock on, or vice versa.
+		 * If so, we don't want to schedule them together.
 		 */
 		for (i = 0; i < n_slots && !conflicts; i++)
 		{
@@ -3423,18 +3447,14 @@ get_next_work_item(ArchiveHandle *AH, TocEntry **first_unprocessed,
 			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])
+
+			if (has_lock_conflicts(te, running_te) ||
+				has_lock_conflicts(running_te, te))
 			{
 				conflicts = true;
 				break;
 			}
 		}
-			}
-		}
 
 		if (conflicts)
 			continue;