HHH-7797 Use unique indexes on nullable columns for DB2. Correctly

handle @UniqueConstraint table annotations on second passes.

hibernate-core/src/main/java/org/hibernate/cfg/Configuration.java

@@ -1540,7 +1540,6 @@ public class Configuration implements Serializable {
 	private void buildUniqueKeyFromColumnNames(Table table, String keyName, String[] columnNames) {
 		keyName = normalizer.normalizeIdentifierQuoting( keyName );
 
-		UniqueKey uc;
 		int size = columnNames.length;
 		Column[] columns = new Column[size];
 		Set<Column> unbound = new HashSet<Column>();
@@ -1559,8 +1558,10 @@ public class Configuration implements Serializable {
 		}
 		for ( Column column : columns ) {
 			if ( table.containsColumn( column ) ) {
-				uc = table.getOrCreateUniqueKey( keyName );
+				Column tableColumn = table.getColumn( column );
-				uc.addColumn( table.getColumn( column ) );
+				tableColumn.setUnique( true );
+				Dialect.getDialect().getUniqueDelegate().generateUniqueKey(
+						table, tableColumn );
 				unbound.remove( column );
 			}
 		}

hibernate-core/src/main/java/org/hibernate/dialect/DB2Dialect.java

@@ -35,6 +35,8 @@ import org.hibernate.dialect.function.NoArgSQLFunction;
 import org.hibernate.dialect.function.SQLFunctionTemplate;
 import org.hibernate.dialect.function.StandardSQLFunction;
 import org.hibernate.dialect.function.VarArgsSQLFunction;
+import org.hibernate.dialect.unique.DB2UniqueDelegate;
+import org.hibernate.dialect.unique.UniqueDelegate;
 import org.hibernate.exception.LockTimeoutException;
 import org.hibernate.exception.spi.SQLExceptionConversionDelegate;
 import org.hibernate.internal.util.JdbcExceptionHelper;
@@ -48,6 +50,8 @@ import org.hibernate.type.descriptor.sql.SqlTypeDescriptor;
  * @author Gavin King
  */
 public class DB2Dialect extends Dialect {
+	
+	private final UniqueDelegate uniqueDelegate;
 
 	public DB2Dialect() {
 		super();
@@ -174,6 +178,8 @@ public class DB2Dialect extends Dialect {
 		registerKeyword( "only" );
 
 		getDefaultProperties().setProperty( Environment.STATEMENT_BATCH_SIZE, NO_BATCH );
+		
+		uniqueDelegate = new DB2UniqueDelegate( this );
 	}
 	@Override
 	public String getLowercaseFunction() {
@@ -451,5 +457,10 @@ public class DB2Dialect extends Dialect {
 			}
 		};
 	}
+	
+	@Override
+	public UniqueDelegate getUniqueDelegate() {
+		return uniqueDelegate;
+	}
 
 }

hibernate-core/src/main/java/org/hibernate/dialect/unique/DB2UniqueDelegate.java

@@ -0,0 +1,109 @@
+/* 
+ * Hibernate, Relational Persistence for Idiomatic Java
+ * 
+ * JBoss, Home of Professional Open Source
+ * Copyright 2012 Red Hat Inc. and/or its affiliates and other contributors
+ * as indicated by the @authors tag. All rights reserved.
+ * See the copyright.txt in the distribution for a
+ * full listing of individual contributors.
+ *
+ * This copyrighted material is made available to anyone wishing to use,
+ * modify, copy, or redistribute it subject to the terms and conditions
+ * of the GNU Lesser General Public License, v. 2.1.
+ * This program is distributed in the hope that it will be useful, but WITHOUT A
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.
+ * You should have received a copy of the GNU Lesser General Public License,
+ * v.2.1 along with this distribution; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA  02110-1301, USA.
+ */
+package org.hibernate.dialect.unique;
+
+import java.util.Iterator;
+
+import org.hibernate.dialect.Dialect;
+import org.hibernate.metamodel.relational.Column;
+import org.hibernate.metamodel.relational.Index;
+import org.hibernate.metamodel.relational.UniqueKey;
+
+/**
+ * DB2 does not allow unique constraints on nullable columns.  Rather than
+ * forcing "not null", use unique *indexes* instead.
+ * 
+ * @author Brett Meyer
+ */
+public class DB2UniqueDelegate extends DefaultUniqueDelegate {
+	
+	public DB2UniqueDelegate( Dialect dialect ) {
+		super( dialect );
+	}
+	
+	@Override
+	public String applyUniquesOnAlter( org.hibernate.mapping.UniqueKey uniqueKey,
+			String defaultCatalog, String defaultSchema ) {
+		if ( hasNullable( uniqueKey ) ) {
+			return org.hibernate.mapping.Index.buildSqlCreateIndexString(
+					dialect, uniqueKey.getName(), uniqueKey.getTable(),
+					uniqueKey.columnIterator(), true, defaultCatalog,
+					defaultSchema );
+		} else {
+			return super.applyUniquesOnAlter(
+					uniqueKey, defaultCatalog, defaultSchema );
+		}
+	}
+	
+	@Override
+	public String applyUniquesOnAlter( UniqueKey uniqueKey ) {
+		if ( hasNullable( uniqueKey ) ) {
+			return Index.buildSqlCreateIndexString(
+					dialect, uniqueKey.getName(), uniqueKey.getTable(),
+					uniqueKey.getColumns(), true );
+		} else {
+			return super.applyUniquesOnAlter( uniqueKey );
+		}
+	}
+	
+	@Override
+	public String dropUniquesOnAlter( org.hibernate.mapping.UniqueKey uniqueKey,
+			String defaultCatalog, String defaultSchema ) {
+		if ( hasNullable( uniqueKey ) ) {
+			return org.hibernate.mapping.Index.buildSqlDropIndexString(
+					dialect, uniqueKey.getTable(), uniqueKey.getName(),
+					defaultCatalog, defaultSchema );
+		} else {
+			return super.dropUniquesOnAlter(
+					uniqueKey, defaultCatalog, defaultSchema );
+		}
+	}
+	
+	@Override
+	public String dropUniquesOnAlter( UniqueKey uniqueKey ) {
+		if ( hasNullable( uniqueKey ) ) {
+			return Index.buildSqlDropIndexString(
+					dialect, uniqueKey.getTable(), uniqueKey.getName() );
+		} else {
+			return super.dropUniquesOnAlter( uniqueKey );
+		}
+	}
+	
+	private boolean hasNullable( org.hibernate.mapping.UniqueKey uniqueKey ) {
+		Iterator iter = uniqueKey.getColumnIterator();
+		while ( iter.hasNext() ) {
+			if ( ( ( org.hibernate.mapping.Column ) iter.next() ).isNullable() ) {
+				return true;
+			}
+		}
+		return false;
+	}
+	
+	private boolean hasNullable( UniqueKey uniqueKey ) {
+		Iterator iter = uniqueKey.getColumns().iterator();
+		while ( iter.hasNext() ) {
+			if ( ( ( Column ) iter.next() ).isNullable() ) {
+				return true;
+			}
+		}
+		return false;
+	}
+}

hibernate-core/src/main/java/org/hibernate/dialect/unique/DefaultUniqueDelegate.java

@@ -35,7 +35,7 @@ import org.hibernate.metamodel.relational.UniqueKey;
  */
 public class DefaultUniqueDelegate implements UniqueDelegate {
 	
-	private final Dialect dialect;
+	protected final Dialect dialect;
 	
 	public DefaultUniqueDelegate( Dialect dialect ) {
 		this.dialect = dialect;
@@ -57,7 +57,12 @@ public class DefaultUniqueDelegate implements UniqueDelegate {
 	}
 	
 	@Override
-	public String applyUniqueToColumn() {
+	public String applyUniqueToColumn( org.hibernate.mapping.Column column ) {
+		return "";
+	}
+	
+	@Override
+	public String applyUniqueToColumn( Column column ) {
 		return "";
 	}
 

hibernate-core/src/main/java/org/hibernate/dialect/unique/UniqueDelegate.java

@@ -68,9 +68,20 @@ public interface UniqueDelegate {
 	 * return the syntax necessary to mutate the column definition
 	 * (usually "unique").
 	 * 
+	 * @param column
 	 * @return String
 	 */
-	public String applyUniqueToColumn();
+	public String applyUniqueToColumn( org.hibernate.mapping.Column column );
+	
+	/**
+	 * If the dialect does not supports unique constraints, this method should
+	 * return the syntax necessary to mutate the column definition
+	 * (usually "unique").
+	 * 
+	 * @param column
+	 * @return String
+	 */
+	public String applyUniqueToColumn( Column column );
 	
 	/**
 	 * If constraints are supported, but not in seperate alter statements,

hibernate-core/src/main/java/org/hibernate/mapping/Index.java

@@ -79,7 +79,6 @@ public class Index implements RelationalModel, Serializable {
 			String defaultCatalog,
 			String defaultSchema
 	) {
-		//TODO handle supportsNotNullUnique=false, but such a case does not exist in the wild so far
 		StringBuilder buf = new StringBuilder( "create" )
 				.append( unique ?
 						" unique" :

hibernate-core/src/main/java/org/hibernate/mapping/Table.java

@@ -425,8 +425,8 @@ public class Table implements RelationalModel, Serializable {
 				if ( column.isUnique() ) {
 					dialect.getUniqueDelegate().generateUniqueKey(
 							this, column );
-					alter.append(
+					alter.append( dialect.getUniqueDelegate()
-							dialect.getUniqueDelegate().applyUniqueToColumn() );
+							.applyUniqueToColumn( column ) );
 				}
 
 				if ( column.hasCheckConstraint() && dialect.supportsColumnCheck() ) {
@@ -526,7 +526,9 @@ public class Table implements RelationalModel, Serializable {
 			
 			if ( col.isUnique() ) {
 				dialect.getUniqueDelegate().generateUniqueKey( this, col );
-				buf.append( dialect.getUniqueDelegate().applyUniqueToColumn() );			}
+				buf.append( dialect.getUniqueDelegate()
+						.applyUniqueToColumn( col ) );
+			}
 				
 			if ( col.hasCheckConstraint() && dialect.supportsColumnCheck() ) {
 				buf.append( " check (" )

hibernate-core/src/main/java/org/hibernate/mapping/UniqueKey.java

@@ -57,17 +57,4 @@ public class UniqueKey extends Constraint {
 				this, defaultCatalog, defaultSchema );
 	}
 
-//	@Override
-//    public boolean isGenerated(Dialect dialect) {
-//		if ( !dialect.supportsUniqueConstraintInCreateAlterTable() ) return false;
-//		if ( dialect.supportsNotNullUnique() ) return true;
-//		
-//		Iterator iter = getColumnIterator();
-//		while ( iter.hasNext() ) {
-//			// Dialect does not support "not null unique" and this column is not null.
-//			if ( ! ( (Column) iter.next() ).isNullable() ) return false;
-//		}
-//		return true;
-//	}
-
 }

hibernate-core/src/main/java/org/hibernate/metamodel/relational/Index.java

@@ -63,7 +63,6 @@ public class Index extends AbstractConstraint implements Constraint {
 			Iterable<Column> columns,
 			boolean unique
 	) {
-		//TODO handle supportsNotNullUnique=false, but such a case does not exist in the wild so far
 		StringBuilder buf = new StringBuilder( "create" )
 				.append( unique ?
 						" unique" :
@@ -89,6 +88,18 @@ public class Index extends AbstractConstraint implements Constraint {
 		return buf.toString();
 	}
 
+	public static String buildSqlDropIndexString(
+			Dialect dialect,
+			TableSpecification table,
+			String name
+	) {
+		return "drop index " +
+				StringHelper.qualify(
+						table.getQualifiedName( dialect ),
+						name
+				);
+	}
+
 	public String sqlConstraintStringInAlterTable(Dialect dialect) {
 		StringBuilder buf = new StringBuilder( " index (" );
 		boolean first = true;

hibernate-core/src/main/java/org/hibernate/metamodel/relational/Table.java

@@ -201,7 +201,8 @@ public class Table extends AbstractTableSpecification implements Exportable {
 
 			if ( col.isUnique() ) {
 				dialect.getUniqueDelegate().generateUniqueKey( this, col );
-				buf.append( dialect.getUniqueDelegate().applyUniqueToColumn() );
+				buf.append( dialect.getUniqueDelegate()
+						.applyUniqueToColumn( col ) );
 			}
 
 			if ( col.getCheckCondition() != null && dialect.supportsColumnCheck() ) {