fix(es): npe when applying scripted update on elasticsearch (#15283)

Author: chakru-r

metadata-io/src/main/java/com/linkedin/metadata/search/elasticsearch/client/shim/impl/Es8SearchClientShim.java

@@ -1641,6 +1641,21 @@ protected void addToProcessor(BulkIngester<?> processor, DocWriteRequest<?> writ
     if (writeRequest instanceof UpdateRequest) {
       UpdateRequest update = (UpdateRequest) writeRequest;
       Script script = convertScript(update.script());
+
+      @SuppressWarnings("rawtypes")
+      UpdateAction.Builder actionBuilder =
+          new UpdateAction.Builder()
+              .detectNoop(update.detectNoop())
+              .docAsUpsert(update.docAsUpsert())
+              .script(script)
+              .upsert(update.upsert());
+
+      // Only set doc if it exists (not present for script-only updates)
+      if (update.doc() != null) {
+        actionBuilder.doc(
+            XContentHelper.convertToMap(update.doc().source(), true, XContentType.JSON).v2());
+      }
+
       operation =
           new BulkOperation(
               new UpdateOperation.Builder<>()
@@ -1651,17 +1666,7 @@ protected void addToProcessor(BulkIngester<?> processor, DocWriteRequest<?> writ
                   .requireAlias(writeRequest.isRequireAlias())
                   .index(writeRequest.index())
                   .routing(writeRequest.routing())
-                  .action(
-                      new UpdateAction.Builder<>()
-                          .doc(
-                              XContentHelper.convertToMap(
-                                      update.doc().source(), true, XContentType.JSON)
-                                  .v2())
-                          .detectNoop(update.detectNoop())
-                          .docAsUpsert(update.docAsUpsert())
-                          .script(script)
-                          .upsert(update.upsert())
-                          .build())
+                  .action(actionBuilder.build())
                   .build());
     } else if (writeRequest instanceof DeleteRequest) {
       DeleteRequest deleteRequest = (DeleteRequest) writeRequest;

metadata-io/src/test/java/com/linkedin/metadata/search/update/ESWriteDAOTest.java

@@ -116,6 +116,7 @@ public void testDeleteDocument() {
     assertEquals(capturedRequest.id(), TEST_DOC_ID);
   }
 
+  @Test
   public void testApplyScriptUpdate() {
     String scriptSource = "ctx._source.field = params.newValue";
     Map<String, Object> scriptParams = new HashMap<>();
@@ -135,6 +136,7 @@ public void testApplyScriptUpdate() {
     assertFalse(capturedRequest.detectNoop());
     assertTrue(capturedRequest.scriptedUpsert());
     assertEquals(NUM_RETRIES, capturedRequest.retryOnConflict());
+    assertNull(capturedRequest.doc()); // For scripted updates, this is null
 
     // Verify script content and parameters
     Script script = capturedRequest.script();