The fields used to determine sort order must be carefully chosen. - * Documents must contain a single term in such a field, - * and the value of the term should indicate the document's relative position in - * a given sort order. The field must be indexed, but should not be tokenized, - * and does not need to be stored (unless you happen to want it back with the - * rest of your document data). In other words: - * - *
document.add (new Field ("byNumber", Integer.toString(x), Field.Store.NO, Field.Index.NOT_ANALYZED));
There are four possible kinds of term values which may be put into - * sorting fields: Integers, Longs, Floats, or Strings. Unless - * {@link SortField SortField} objects are specified, the type of value - * in the field is determined by parsing the first term in the field. - * - *
Integer term values should contain only digits and an optional
- * preceding negative sign. Values must be base 10 and in the range
- * Integer.MIN_VALUE and Integer.MAX_VALUE inclusive.
- * Documents which should appear first in the sort
- * should have low value integers, later documents high values
- * (i.e. the documents should be numbered 1..n where
- * 1 is the first and n the last).
- *
- *
Long term values should contain only digits and an optional
- * preceding negative sign. Values must be base 10 and in the range
- * Long.MIN_VALUE and Long.MAX_VALUE inclusive.
- * Documents which should appear first in the sort
- * should have low value integers, later documents high values.
- *
- *
Float term values should conform to values accepted by
- * {@link Float Float.valueOf(String)} (except that NaN
- * and Infinity are not supported).
- * Documents which should appear first in the sort
- * should have low values, later documents high values.
- *
- *
String term values can contain any valid String, but should - * not be tokenized. The values are sorted according to their - * {@link Comparable natural order}. Note that using this type - * of term value has higher memory requirements than the other - * two types. - * - *
One of these objects can be - * used multiple times and the sort order changed between usages. - * - *
This class is thread safe. - * - *
Sorting uses of caches of term values maintained by the
- * internal HitQueue(s). The cache is static and contains an integer
- * or float array of length IndexReader.maxDoc() for each field
- * name for which a sort is performed. In other words, the size of the
- * cache in bytes is:
- *
- *
4 * IndexReader.maxDoc() * (# of different fields actually used to sort)
- *
- *
For String fields, the cache is larger: in addition to the - * above array, the value of every term in the field is kept in memory. - * If there are many unique terms in the field, this could - * be quite large. - * - *
Note that the size of the cache is not affected by how many - * fields are in the index and might be used to sort - only by - * the ones actually used to sort a result set. - * - *
Created: Feb 12, 2004 10:53:57 AM
- *
- * @since lucene 1.4
- */
-public class Sort
-implements Serializable {
-
- /**
- * Represents sorting by computed relevance. Using this sort criteria returns
- * the same results as calling
- * {@link Searcher#search(Query,int) Searcher#search()}without a sort criteria,
- * only with slightly more overhead.
- */
- public static final Sort RELEVANCE = new Sort();
-
- /** Represents sorting by index order. */
- public static final Sort INDEXORDER = new Sort(SortField.FIELD_DOC);
-
- // internal representation of the sort criteria
- SortField[] fields;
-
- /**
- * Sorts by computed relevance. This is the same sort criteria as calling
- * {@link Searcher#search(Query,int) Searcher#search()}without a sort criteria,
- * only with slightly more overhead.
- */
- public Sort() {
- this(SortField.FIELD_SCORE);
- }
-
- /** Sorts by the criteria in the given SortField. */
- public Sort(SortField field) {
- setSort(field);
- }
-
- /** Sorts in succession by the criteria in each SortField. */
- public Sort(SortField... fields) {
- setSort(fields);
- }
-
- /** Sets the sort to the given criteria. */
- public void setSort(SortField field) {
- this.fields = new SortField[] { field };
- }
-
- /** Sets the sort to the given criteria in succession. */
- public void setSort(SortField... fields) {
- this.fields = fields;
- }
-
- /**
- * Representation of the sort criteria.
- * @return Array of SortField objects used in this sort criteria
- */
- public SortField[] getSort() {
- return fields;
- }
-
- @Override
- public String toString() {
- StringBuilder buffer = new StringBuilder();
-
- for (int i = 0; i < fields.length; i++) {
- buffer.append(fields[i].toString());
- if ((i+1) < fields.length)
- buffer.append(',');
- }
-
- return buffer.toString();
- }
-
- /** Returns true if o is equal to this. */
- @Override
- public boolean equals(Object o) {
- if (this == o) return true;
- if (!(o instanceof Sort)) return false;
- final Sort other = (Sort)o;
- return Arrays.equals(this.fields, other.fields);
- }
-
- /** Returns a hash code value for this object. */
- @Override
- public int hashCode() {
- return 0x45aaf665 + Arrays.hashCode(fields);
- }
-}