db2dialect.java

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//$Id: DB2Dialect.java,v 1.7.2.7 2004/01/27 22:01:41 oneovthafew Exp $
package net.sf.hibernate.dialect;

import java.sql.Types;

import net.sf.hibernate.cfg.Environment;

/**
 * An SQL dialect for DB2.
 * @author Gavin King
 */
public class DB2Dialect extends Dialect {
	
	public DB2Dialect() {
		super();
		registerColumnType( Types.BIT, "SMALLINT" );
		registerColumnType( Types.BIGINT, "BIGINT" );
		registerColumnType( Types.SMALLINT, "SMALLINT" );
		registerColumnType( Types.TINYINT, "SMALLINT" );
		registerColumnType( Types.INTEGER, "INTEGER" );
		registerColumnType( Types.CHAR, "CHAR(1)" );
		registerColumnType( Types.VARCHAR, "VARCHAR($l)" );
		registerColumnType( Types.FLOAT, "FLOAT" );
		registerColumnType( Types.DOUBLE, "DOUBLE" );
		registerColumnType( Types.DATE, "DATE" );
		registerColumnType( Types.TIME, "TIME" );
		registerColumnType( Types.TIMESTAMP, "TIMESTAMP" );
		registerColumnType( Types.VARBINARY, "VARCHAR($l) FOR BIT DATA" );
		registerColumnType( Types.NUMERIC, "NUMERIC(19, $l)" );
		registerColumnType( Types.BLOB, "BLOB($l)" );
		registerColumnType( Types.CLOB, "CLOB($l)" );
		
		getDefaultProperties().setProperty(Environment.USE_OUTER_JOIN, "true");
		getDefaultProperties().setProperty(Environment.STATEMENT_BATCH_SIZE, NO_BATCH);
	}
	
	public String getAddColumnString() {
		return "add column";
	}
	public boolean dropConstraints() {
		return false;
	}
	public boolean supportsIdentityColumns() {
		return true;
	}
	public String getIdentitySelectString() {
		return "values IDENTITY_VAL_LOCAL()";
	}
	public String getIdentityColumnString() {
		return "not null generated by default as identity";
	}
	public String getIdentityInsertString() {
		return "default";
	}
	
	public String getSequenceNextValString(String sequenceName) {
		return "values nextval for " + sequenceName;
	}
	public String getCreateSequenceString(String sequenceName) {
		return "create sequence " + sequenceName;
	}
	public String getDropSequenceString(String sequenceName) {
		return "drop sequence " + sequenceName + " restrict";
	}
	
	public boolean supportsSequences() {
		return true;
	}

	public boolean supportsLimit() {
		return true;
	}

	public String getLimitString(String sql, boolean hasOffset) {
		StringBuffer rownumber = new StringBuffer(50)
			.append(" rownumber() over(");
		int orderByIndex = sql.toLowerCase().indexOf("order by");
		if (orderByIndex>0) rownumber.append( sql.substring(orderByIndex) );
		rownumber.append(") as row_,");
		StringBuffer pagingSelect = new StringBuffer( sql.length()+100 )
			.append("select * from ( ")
			.append(sql)
			.insert( getAfterSelectInsertPoint(sql), rownumber.toString() )
			.append(" ) as temp_ where row_ ");
		if (hasOffset) {
			pagingSelect.append("between ?+1 and ?");
		}
		else {
			pagingSelect.append("<= ?");
		}
		return pagingSelect.toString();
	}

	public boolean useMaxForLimit() {
		return true;
	}

	private static int getAfterSelectInsertPoint(String sql) {
		return 16 + ( sql.startsWith("select distinct") ? 15 : 6 );
	}
}