Add support for reloading the SPI for KnnVectorsFormat class (#13394)

Signed-off-by: Navneet Verma <navneev@amazon.com>

lucene/CHANGES.txt

@@ -413,6 +413,8 @@ Other
 * GITHUB#13077: Add public getter for SynonymQuery#field (Andrey Bozhko)
 
 
+* GITHUB#13393: Add support for reloading the SPI for KnnVectorsFormat class (Navneet Verma)
+
 ======================== Lucene 9.10.0 =======================
 
 API Changes

lucene/core/src/java/org/apache/lucene/codecs/KnnVectorsFormat.java

@@ -68,6 +68,19 @@ public abstract class KnnVectorsFormat implements NamedSPILoader.NamedSPI {
     return name;
   }
 
+  /**
+   * Reloads the KnnVectorsFormat list from the given {@link ClassLoader}.
+   *
+   * <p><b>NOTE:</b> Only new KnnVectorsFormat are added, existing ones are never removed or
+   * replaced.
+   *
+   * <p><em>This method is expensive and should only be called for discovery of new KnnVectorsFormat
+   * on the given classpath/classloader!</em>
+   */
+  public static void reloadKnnVectorsFormat(ClassLoader classloader) {
+    Holder.getLoader().reload(classloader);
+  }
+
   /** looks up a format by name */
   public static KnnVectorsFormat forName(String name) {
     return Holder.getLoader().lookup(name);