From ca3afd2f0a05791a0e47f7ae3cdae3f90a594c70 Mon Sep 17 00:00:00 2001
From: Andrew Dunstan <andrew@dunslane.net>
Date: Sun, 12 Apr 2009 21:02:44 +0000
Subject: [PATCH] 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 | 44 ++++++++++++++++++++--------
 1 file changed, 32 insertions(+), 12 deletions(-)

diff --git a/src/bin/pg_dump/pg_backup_archiver.c b/src/bin/pg_dump/pg_backup_archiver.c
index 5201e60184..0245e060de 100644
--- a/src/bin/pg_dump/pg_backup_archiver.c
+++ b/src/bin/pg_dump/pg_backup_archiver.c
@@ -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++)
 		{
@@ -3423,16 +3447,12 @@ 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++)
+
+			if (has_lock_conflicts(te, running_te) ||
+				has_lock_conflicts(running_te, te))
 			{
-				for (k = 0; k < running_te->nLockDeps; k++)
-				{
-					if (te->lockDeps[j] == running_te->lockDeps[k])
-					{
-						conflicts = true;
-						break;
-					}
-				}
+				conflicts = true;
+				break;
 			}
 		}
 
-- 
2.30.2