spike-liu commented on a change in pull request #678:
URL: https://github.com/apache/lucene/pull/678#discussion_r807563855
##########
File path: lucene/core/src/java/org/apache/lucene/index/Terms.java
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@@ -124,6 +124,69 @@ protected BytesRef nextSeekTerm(BytesRef term) throws
IOException {
/** Zero-length array of {@link Terms}. */
public static final Terms[] EMPTY_ARRAY = new Terms[0];
+ /** An empty {@link Terms} which returns no terms */
+ public static Terms emptyTerms() {
+ return new Terms() {
+ @Override
+ public TermsEnum iterator() throws IOException {
+ return TermsEnum.EMPTY;
+ }
+
+ @Override
+ public long size() throws IOException {
+ return 0;
+ }
+
+ @Override
+ public long getSumTotalTermFreq() throws IOException {
+ return 0;
+ }
+
+ @Override
+ public long getSumDocFreq() throws IOException {
+ return 0;
+ }
+
+ @Override
+ public int getDocCount() throws IOException {
+ return 0;
+ }
+
+ @Override
+ public boolean hasFreqs() {
+ return false;
+ }
+
+ @Override
+ public boolean hasOffsets() {
+ return false;
+ }
+
+ @Override
+ public boolean hasPositions() {
+ return false;
+ }
+
+ @Override
+ public boolean hasPayloads() {
+ return false;
+ }
+ };
+ }
+
+ /**
+ * Returns the {@link Terms} index for this field, or {@link #emptyTerms} if
it has none.
+ * @return terms instance, or an empty instance if {@code field} does not
exist in this reader
+ * @throws IOException if an I/O error occurs.
+ */
+ public static Terms terms(LeafReader reader, String field) throws
IOException {
Review comment:
fixed.
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