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HHH-9300 - DB2Dialect generates invalid order by clause

This commit is contained in:
Steve Ebersole 2015-03-24 23:49:09 -05:00
parent a4b5cf4597
commit 4e0f2b3a7b
1 changed files with 49 additions and 0 deletions
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49
hibernate-core/src/main/java/org/hibernate/dialect/DB2Dialect.java
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@ -27,8 +27,10 @@ import java.sql.CallableStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Types;
import java.util.Locale;
import org.hibernate.JDBCException;
import org.hibernate.NullPrecedence;
import org.hibernate.cfg.Environment;
import org.hibernate.dialect.function.AvgWithArgumentCastFunction;
import org.hibernate.dialect.function.NoArgSQLFunction;
@ -43,7 +45,10 @@ import org.hibernate.dialect.unique.UniqueDelegate;
import org.hibernate.engine.spi.RowSelection;
import org.hibernate.exception.LockTimeoutException;
import org.hibernate.exception.spi.SQLExceptionConversionDelegate;
import org.hibernate.internal.CoreLogging;
import org.hibernate.internal.CoreMessageLogger;
import org.hibernate.internal.util.JdbcExceptionHelper;
import org.hibernate.internal.util.StringHelper;
import org.hibernate.type.StandardBasicTypes;
import org.hibernate.type.descriptor.sql.SmallIntTypeDescriptor;
import org.hibernate.type.descriptor.sql.SqlTypeDescriptor;
@ -54,6 +59,7 @@ import org.hibernate.type.descriptor.sql.SqlTypeDescriptor;
* @author Gavin King
*/
public class DB2Dialect extends Dialect {
private static final CoreMessageLogger log = CoreLogging.messageLogger( DB2Dialect.class );
private static final AbstractLimitHandler LIMIT_HANDLER = new AbstractLimitHandler() {
@Override
@ -524,4 +530,47 @@ public class DB2Dialect extends Dialect {
return LIMIT_HANDLER;
}
/**
* DB2 allows NULLS LAST only if the order is ASC, and NULLS FIRST only if the order is DESC.
* @param expression The SQL order expression. In case of {@code @OrderBy} annotation user receives property placeholder
* (e.g. attribute name enclosed in '{' and '}' signs).
* @param collation Collation string in format {@code collate IDENTIFIER}, or {@code null}
* if expression has not been explicitly specified.
* @param order Order direction. Possible values: {@code asc}, {@code desc}, or {@code null}
* if expression has not been explicitly specified.
* @param nullPrecedence Nulls precedence. Default value: {@link NullPrecedence#NONE}.
*
* @return
*/
@Override
public String renderOrderByElement(String expression, String collation, String order, NullPrecedence nullPrecedence) {
// DB2 FTW!
if ( nullPrecedence == null || nullPrecedence == NullPrecedence.NONE ) {
return super.renderOrderByElement( expression, collation, order, NullPrecedence.NONE );
}
if ( nullPrecedence == NullPrecedence.FIRST ) {
// an explicit NullPrecedence request for NULLS FIRST
if ( order == null || "asc".equals( order ) ) {
// ASC + NULLS FIRST is ok, but unnecessary
return super.renderOrderByElement( expression, collation, order, NullPrecedence.NONE );
}
else {
// DESC + NULLS FIRST is not supported, so hack it
return "order by case when " + expression + " is null then 0 else 1 end, " + expression + " desc";
}
}
else {
// an explicit NullPrecedence request for NULLS LAST
if ( order == null || "asc".equals( order ) ) {
// ASC + NULLS LAST is not supported, so hack it
return "order by case when " + expression + " is null then 1 else 0 end, " + expression + " asc";
}
else {
// DESC + NULLS LAST is ok, but unnecessary
return super.renderOrderByElement( expression, collation, order, NullPrecedence.NONE );
}
}
}
}