/**
* Creates an expression accessing a given named field from a record.
*
* <p>NOTE: Be careful choosing the value of {@code caseSensitive}. If the field name was supplied
* by an end-user (e.g. as a column alias in SQL), use your session's case-sensitivity setting.
* Only hard-code {@code true} if you are sure that the field name is internally generated.
* Hard-coding {@code false} is almost certainly wrong.
*
* @param expr Expression yielding a record
* @param fieldName Name of field in record
* @param caseSensitive Whether match is case-sensitive
* @return Expression accessing a given named field
*/
public RexNode makeFieldAccess(RexNode expr, String fieldName, boolean caseSensitive) {
final RelDataType type = expr.getType();
final RelDataTypeField field = type.getField(fieldName, caseSensitive, false);
if (field == null) {
throw Util.newInternal("Type '" + type + "' has no field '" + fieldName + "'");
}
return makeFieldAccessInternal(expr, field);
}
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<>(columnNameList.size());
for (String name : columnNameList) {
RelDataTypeField field = type.getField(name, caseSensitive, false);
fields.add(type.getFieldList().get(field.getIndex()));
}
return typeFactory.createStructType(fields);
}
/**
* Looks up a field with a given name, returning null if not found.
*
* @param caseSensitive Whether match is case-sensitive
* @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) {
return rowType.getField(columnName, caseSensitive, false);
}