org.hibernate.dialect.unique

Interface UniqueDelegate

All Known Implementing Classes:

DB2UniqueDelegate, DefaultUniqueDelegate, InformixUniqueDelegate

public interface UniqueDelegate

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

1. Add a unique constraint via separate alter table statements. See getAlterTableToAddUniqueKeyCommand(org.hibernate.mapping.UniqueKey, org.hibernate.boot.Metadata). Also, see getAlterTableToDropUniqueKeyCommand(org.hibernate.mapping.UniqueKey, org.hibernate.boot.Metadata)
2. Add a unique constraint via dialect-specific syntax in table create statement. See getTableCreationUniqueConstraintsFragment(org.hibernate.mapping.Table)
3. Add "unique" syntax to the column itself. See getColumnDefinitionUniquenessFragment(org.hibernate.mapping.Column)

#1 & #2 are preferred, if possible; #3 should be solely a fall-back. See HHH-7797.

Method Summary

Modifier and Type	Method and Description
String	getAlterTableToAddUniqueKeyCommand(UniqueKey uniqueKey, Metadata metadata) Get the SQL ALTER TABLE command to be used to create the given UniqueKey.
String	getAlterTableToDropUniqueKeyCommand(UniqueKey uniqueKey, Metadata metadata) Get the SQL ALTER TABLE command to be used to drop the given UniqueKey.
String	getColumnDefinitionUniquenessFragment(Column column) Get the fragment that can be used to make a column unique as part of its column definition.
String	getTableCreationUniqueConstraintsFragment(Table table) Get the fragment that can be used to apply unique constraints as part of table creation.

Method Detail

getColumnDefinitionUniquenessFragment

String getColumnDefinitionUniquenessFragment(Column column)

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

Parameters:

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

getTableCreationUniqueConstraintsFragment

String getTableCreationUniqueConstraintsFragment(Table table)

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.

Parameters:

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!

getAlterTableToAddUniqueKeyCommand

String getAlterTableToAddUniqueKeyCommand(UniqueKey uniqueKey,
                                          Metadata metadata)

Get the SQL ALTER TABLE command to be used to create the given UniqueKey.

Parameters:

uniqueKey - The UniqueKey instance. Contains all information about the columns

metadata - Access to the bootstrap mapping information

Returns:

The ALTER TABLE command

getAlterTableToDropUniqueKeyCommand

String getAlterTableToDropUniqueKeyCommand(UniqueKey uniqueKey,
                                           Metadata metadata)

Get the SQL ALTER TABLE command to be used to drop the given UniqueKey.

Parameters:

uniqueKey - The UniqueKey instance. Contains all information about the columns

metadata - Access to the bootstrap mapping information

Returns:

The ALTER TABLE command