GH1565 Add alias in "for update" clause to entity loading query containing outer join if database (e.g Postgres) does not support locking with outer join

Author: Doan Van Tuan

src/NHibernate.Test/NHSpecificTest/GH1565/Mappings.hbm.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="NHibernate.Test"
+                   namespace="NHibernate.Test.NHSpecificTest.GH1565">
+  
+  <class name="MainEntity">
+    <id name="Id" unsaved-value="0">
+      <generator class="native" />
+    </id>
+
+    <join table="EntityData" inverse="true">
+      <key column="EntityId"/>
+      <property name="Data" />
+    </join>
+  </class>
+</hibernate-mapping>

src/NHibernate.Test/NHSpecificTest/GH1565/PostgresOuterJoinLockTest.cs

@@ -0,0 +1,68 @@
+using NHibernate.Cfg;
+using NHibernate.Dialect;
+using NUnit.Framework;
+
+namespace NHibernate.Test.NHSpecificTest.GH1565
+{
+    [TestFixture]
+    public class PostgresOuterJoinLockTest : BugTestCase
+    {
+	    [Test]
+	    public void LockWithOuterJoin_ShouldBePossible()
+	    {
+		    using (var session = OpenSession())
+		    {
+			    using (var transaction = session.BeginTransaction())
+			    {
+				    var entity = session.Get<MainEntity>(id, LockMode.Upgrade);
+				    Assert.That(entity.Id, Is.EqualTo(id));
+				    transaction.Rollback();
+			    }
+		    }
+	    }
+
+		private int id;
+        protected override void OnSetUp()
+        {
+            base.OnSetUp();
+            using (var session = OpenSession())
+            {
+                using (var transaction = session.BeginTransaction())
+                {
+                    session.FlushMode = FlushMode.Auto;
+	                var entity = new MainEntity();
+                    session.Save(entity);
+                    transaction.Commit();
+                    id = entity.Id;
+                }
+            }
+        }
+
+        protected override void OnTearDown()
+        {
+            base.OnTearDown();
+            using (var session = OpenSession())
+            {
+                session.CreateSQLQuery("delete from MainEntity").ExecuteUpdate();
+            }
+        }
+
+        protected override bool AppliesTo(Dialect.Dialect dialect)
+        {
+            return dialect is PostgreSQLDialect;
+        }
+
+	    protected override void Configure(Configuration configuration)
+	    {
+		    configuration.SetProperty(Cfg.Environment.Dialect, typeof(PostgreSQL83Dialect).FullName);
+		    configuration.SetProperty(Cfg.Environment.ConnectionDriver, typeof(Driver.NpgsqlDriver).FullName);
+	    }
+    }
+
+    public class MainEntity
+    {
+	    public virtual int Id { get; set; } = 0;
+
+		public virtual string Data { get; set; }
+    }
+}

src/NHibernate/Dialect/PostgreSQLDialect.cs

@@ -316,6 +316,7 @@ public override string CurrentTimestampSelectString
 
 		public override bool SupportsUnboundedLobLocatorMaterialization => false;
 
+		public override bool SupportsOuterJoinForUpdate => false;
 		#endregion
 
 		[Serializable]

src/NHibernate/Loader/AbstractEntityJoinWalker.cs

@@ -118,7 +118,7 @@ private void InitStatementString(SqlString projection, SqlString condition, SqlS
 			JoinFragment ojf = MergeOuterJoins(associations);
 
 			SqlSelectBuilder select = new SqlSelectBuilder(Factory)
-				.SetLockMode(lockMode)
+				.SetLockMode(lockMode, alias)
 				.SetSelectClause(selectClause)
 				.SetFromClause(Dialect.AppendLockHint(lockMode, persister.FromTableFragment(alias)) +persister.FromJoinFragment(alias, true, true))
 				.SetWhereClause(condition)

src/NHibernate/SqlCommand/SqlSelectBuilder.cs

@@ -21,7 +21,9 @@ public class SqlSelectBuilder : SqlBaseBuilder, ISqlStringBuilder
 		private SqlString groupByClause;
 		private SqlString havingClause;
 		private LockMode lockMode;
+		private string aliasToLock;
 		private string comment;
+		private bool hasOuterJoin = false;
 
 		public SqlSelectBuilder(ISessionFactoryImplementor factory)
 			: base(factory.Dialect, factory) {}
@@ -40,6 +42,7 @@ public SqlSelectBuilder SetComment(string comment)
 		public SqlSelectBuilder SetFromClause(string fromClause)
 		{
 			this.fromClause = fromClause;
+			hasOuterJoin = hasOuterJoin || fromClause.ToLowerInvariant().Contains("left outer join");
 			return this;
 		}
 
@@ -110,6 +113,9 @@ public SqlSelectBuilder SetOuterJoins(SqlString outerJoinsAfterFrom, SqlString o
 			}
 
 			this.outerJoinsAfterWhere = tmpOuterJoinsAfterWhere;
+
+			hasOuterJoin = hasOuterJoin || 
+			               outerJoinsAfterFrom != null && outerJoinsAfterFrom.ToString().ToLowerInvariant().Contains("outer join");
 			return this;
 		}
 
@@ -181,9 +187,10 @@ public SqlSelectBuilder SetHavingClause(SqlString havingSqlString)
 			return this;
 		}
 
-		public SqlSelectBuilder SetLockMode(LockMode lockMode)
+		public SqlSelectBuilder SetLockMode(LockMode lockMode, string alias)
 		{
 			this.lockMode = lockMode;
+			aliasToLock = alias;
 			return this;
 		}
 
@@ -267,7 +274,7 @@ public SqlString ToSqlString()
 
 			if (lockMode != null)
 			{
-				sqlBuilder.Add(Dialect.GetForUpdateString(lockMode));
+				sqlBuilder.Add(GetForUpdateString());
 			}
 
 			if (log.IsDebugEnabled())
@@ -291,6 +298,19 @@ public SqlString ToSqlString()
 			return sqlBuilder.ToSqlString();
 		}
 
+		private string GetForUpdateString()
+		{
+			if (!Dialect.SupportsOuterJoinForUpdate && hasOuterJoin)
+			{
+				if (Equals(lockMode, LockMode.Upgrade))
+					return Dialect.GetForUpdateString(aliasToLock);
+				if (Equals(lockMode, LockMode.UpgradeNoWait))
+					return Dialect.GetForUpdateNowaitString(aliasToLock);
+			}
+
+			return Dialect.GetForUpdateString(lockMode);
+		}
+
 		#endregion
 	}
 }