/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
 * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
 */
package org.hibernate.dialect.unique;

import org.hibernate.boot.Metadata;
import org.hibernate.mapping.UniqueKey;

Dialect-level delegate in charge of applying "uniqueness" to a column.  Uniqueness can be defined
in 1 of 3 ways:

    
 Add a unique constraint via separate alter table statements. See getAlterTableToAddUniqueKeyCommand. Also, see getAlterTableToDropUniqueKeyCommand 
    
 Add a unique constraint via dialect-specific syntax in table create statement. See getTableCreationUniqueConstraintsFragment 
    
 Add "unique" syntax to the column itself. See getColumnDefinitionUniquenessFragment 

#1 & #2 are preferred, if possible; #3 should be solely a fall-back.
See HHH-7797.
Author:
Brett Meyer/**
 * Dialect-level delegate in charge of applying "uniqueness" to a column.  Uniqueness can be defined
 * in 1 of 3 ways:<ol>
 *     <li>
 *         Add a unique constraint via separate alter table statements.  See {@link #getAlterTableToAddUniqueKeyCommand}.
 *         Also, see {@link #getAlterTableToDropUniqueKeyCommand}
 *     </li>
 *     <li>
 *			Add a unique constraint via dialect-specific syntax in table create statement.  See
 *			{@link #getTableCreationUniqueConstraintsFragment}
 *     </li>
 *     <li>
 *         Add "unique" syntax to the column itself.  See {@link #getColumnDefinitionUniquenessFragment}
 *     </li>
 * </ol>
 *
 * #1 & #2 are preferred, if possible; #3 should be solely a fall-back.
 * 
 * See HHH-7797.
 * 
 * @author Brett Meyer
 */
public interface UniqueDelegate {
	
Get the fragment that can be used to make a column unique as part of its column definition.

This is intended for dialects which do not support unique constraints
Params:
column – The column to which to apply the unique
Returns:
The fragment (usually "unique"), empty string indicates the uniqueness will be indicated using a
different approach/**
	 * Get the fragment that can be used to make a column unique as part of its column definition.
	 * <p/>
	 * This is intended for dialects which do not support unique constraints
	 * 
	 * @param column The column to which to apply the unique
	 *
	 * @return The fragment (usually "unique"), empty string indicates the uniqueness will be indicated using a
	 * different approach
	 */
	public String getColumnDefinitionUniquenessFragment(org.hibernate.mapping.Column column);

	
Get the fragment that can be used to apply unique constraints as part of table creation. The implementation should iterate over the UniqueKey instances for the given table (see Table.getUniqueKeyIterator() and generate the whole fragment for all unique keys 

Intended for Dialects which support unique constraint definitions, but just not in separate ALTER statements.
Params:
table – The table for which to generate the unique constraints fragment
Returns:
The fragment, typically in the form ", unique(col1, col2), unique( col20)". NOTE: The leading comma is important!/**
	 * Get the fragment that can be used to apply unique constraints as part of table creation.  The implementation
	 * should iterate over the {@link org.hibernate.mapping.UniqueKey} instances for the given table (see
	 * {@link org.hibernate.mapping.Table#getUniqueKeyIterator()} and generate the whole fragment for all
	 * unique keys
	 * <p/>
	 * Intended for Dialects which support unique constraint definitions, but just not in separate ALTER statements.
	 *
	 * @param table The table for which to generate the unique constraints fragment
	 *
	 * @return The fragment, typically in the form {@code ", unique(col1, col2), unique( col20)"}.  NOTE: The leading
	 * comma is important!
	 */
	public String getTableCreationUniqueConstraintsFragment(org.hibernate.mapping.Table table);

	
Get the SQL ALTER TABLE command to be used to create the given UniqueKey.
Params:
uniqueKey – The UniqueKey instance.  Contains all information about the columns
metadata – Access to the bootstrap mapping information
Returns:
The ALTER TABLE command/**
	 * Get the SQL ALTER TABLE command to be used to create the given UniqueKey.
	 *
	 * @param uniqueKey The UniqueKey instance.  Contains all information about the columns
	 * @param metadata Access to the bootstrap mapping information
	 *
	 * @return The ALTER TABLE command
	 */
	public String getAlterTableToAddUniqueKeyCommand(UniqueKey uniqueKey, Metadata metadata);

	
Get the SQL ALTER TABLE command to be used to drop the given UniqueKey.
Params:
uniqueKey – The UniqueKey instance.  Contains all information about the columns
metadata – Access to the bootstrap mapping information
Returns:
The ALTER TABLE command/**
	 * Get the SQL ALTER TABLE command to be used to drop the given UniqueKey.
	 *
	 * @param uniqueKey The UniqueKey instance.  Contains all information about the columns
	 * @param metadata Access to the bootstrap mapping information
	 *
	 * @return The ALTER TABLE command
	 */
	public String getAlterTableToDropUniqueKeyCommand(UniqueKey uniqueKey, Metadata metadata);

}