/**
* Looks up a field with a given name, returning null if not found.
*
* @param rowType Row type
* @param columnName Field name
* @return Field, or null if not found
*/
public static RelDataTypeField lookupField(
boolean caseSensitive, final RelDataType rowType, String columnName) {
RelDataTypeField field = rowType.getField(columnName, caseSensitive);
if (field != null) {
return field;
}
// If record type is flagged as having "any field you ask for",
// return a type. (TODO: Better way to mark accommodating types.)
RelDataTypeField extra = RelDataTypeImpl.extra(rowType);
if (extra != null) {
return new RelDataTypeFieldImpl(columnName, -1, extra.getType());
}
return null;
}
public static RelDataType createTypeFromProjection(
RelDataType type,
List<String> columnNameList,
RelDataTypeFactory typeFactory,
boolean caseSensitive) {
// If the names in columnNameList and type have case-sensitive differences,
// the resulting type will use those from type. These are presumably more
// canonical.
final List<RelDataTypeField> fields = new ArrayList<RelDataTypeField>(columnNameList.size());
for (String name : columnNameList) {
RelDataTypeField field = type.getField(name, caseSensitive);
fields.add(type.getFieldList().get(field.getIndex()));
}
return typeFactory.createStructType(fields);
}
/**
* Returns the "extra" field in a row type whose presence signals that fields will come into
* existence just by asking for them.
*
* @param rowType Row type
* @return The "extra" field, or null
*/
public static RelDataTypeField extra(RelDataType rowType) {
// Even in a case-insensitive connection, the name must be precisely
// "_extra".
return rowType.getField("_extra", true);
}