From 77bf727cdae84aa4e11d421da4ca5d70dc2b4f1c Mon Sep 17 00:00:00 2001
From: Valery Kharseko <vharseko@3a-systems.ru>
Date: Mon, 03 Aug 2026 07:57:42 +0000
Subject: [PATCH] [#808] fix MS SQL MERGE upsert conversion deadlock with WITH (HOLDLOCK, UPDLOCK) (#810)
---
opendj-server-legacy/src/main/java/org/opends/server/backends/jdbc/Storage.java | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/opendj-server-legacy/src/main/java/org/opends/server/backends/jdbc/Storage.java b/opendj-server-legacy/src/main/java/org/opends/server/backends/jdbc/Storage.java
index 65a1289..9b4dfff 100644
--- a/opendj-server-legacy/src/main/java/org/opends/server/backends/jdbc/Storage.java
+++ b/opendj-server-legacy/src/main/java/org/opends/server/backends/jdbc/Storage.java
@@ -389,8 +389,8 @@
statement.setBytes(3, value.toByteArray());
return (execute(statement) == 1 && statement.getUpdateCount() > 0);
}
- }else if (driverName.contains("microsoft")) { //ANSI MERGE with ; WITH (HOLDLOCK) makes the upsert atomic: without it SQL Server MERGE can race two concurrent NOT MATCHED inserts of the same key into a PRIMARY KEY violation
- try (final PreparedStatement statement = con.prepareStatement("merge into " + getTableName(treeName) + " WITH (HOLDLOCK) old using (select ? h,? k,? v) new on (old.h=new.h and old.k=new.k) WHEN MATCHED THEN UPDATE SET old.v=new.v WHEN NOT MATCHED THEN INSERT (h,k,v) VALUES (new.h,new.k,new.v);")) {
+ }else if (driverName.contains("microsoft")) { //ANSI MERGE with ; WITH (HOLDLOCK) makes the upsert atomic: without it SQL Server MERGE can race two concurrent NOT MATCHED inserts of the same key into a PRIMARY KEY violation. UPDLOCK is required on top of it: with HOLDLOCK alone the search phase takes a shared lock that the WHEN MATCHED update then has to convert to an exclusive one, so two concurrent upserts of the same key deadlock on the conversion; an update lock is taken right away and makes the second transaction wait instead
+ try (final PreparedStatement statement = con.prepareStatement("merge into " + getTableName(treeName) + " WITH (HOLDLOCK, UPDLOCK) old using (select ? h,? k,? v) new on (old.h=new.h and old.k=new.k) WHEN MATCHED THEN UPDATE SET old.v=new.v WHEN NOT MATCHED THEN INSERT (h,k,v) VALUES (new.h,new.k,new.v);")) {
statement.setString(1, key2hash.get(ByteBuffer.wrap(key.toByteArray())));
statement.setBytes(2, real2db(key.toByteArray()));
statement.setBytes(3, value.toByteArray());
--
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