Override default fadvice to SEQUENTIAL

This fixes the regression introduced by gcs-connector v3.

Author: shunping

sdks/java/extensions/google-cloud-platform-core/src/main/java/org/apache/beam/sdk/extensions/gcp/options/GcsOptions.java

@@ -60,7 +60,13 @@ public interface GcsOptions extends ApplicationNameOptions, GcpOptions, Pipeline
   class GcsReadOptionsFactory implements DefaultValueFactory<GoogleCloudStorageReadOptions> {
     @Override
     public GoogleCloudStorageReadOptions create(PipelineOptions options) {
-      return GoogleCloudStorageReadOptions.DEFAULT;
+      // In gcs-connector v3, GoogleCloudStorageReadOptions.DEFAULT changed fadvise from SEQUENTIAL
+      // to AUTO. Beam workloads default to SEQUENTIAL to preserve expected sequential read
+      // throughput and caching behavior.
+      return GoogleCloudStorageReadOptions.DEFAULT
+          .toBuilder()
+          .setFadvise(GoogleCloudStorageReadOptions.Fadvise.SEQUENTIAL)
+          .build();
     }
   }
 

sdks/java/extensions/google-cloud-platform-core/src/test/java/org/apache/beam/sdk/extensions/gcp/options/GcsOptionsTest.java

@@ -86,7 +86,7 @@ public void testGoogleCloudStorageReadOptionsSerialization() throws Exception {
     GcsOptions options = PipelineOptionsFactory.as(GcsOptions.class);
     GoogleCloudStorageReadOptions readOptions =
         GoogleCloudStorageReadOptions.builder()
-            .setFadvise(GoogleCloudStorageReadOptions.Fadvise.SEQUENTIAL)
+            .setFadvise(GoogleCloudStorageReadOptions.Fadvise.RANDOM)
             .setFastFailOnNotFoundEnabled(false)
             .setMinRangeRequestSize(12345L)
             .build();
@@ -102,7 +102,7 @@ public void testGoogleCloudStorageReadOptionsSerialization() throws Exception {
 
     assertNotNull(deserializedReadOptions);
     assertEquals(
-        GoogleCloudStorageReadOptions.Fadvise.SEQUENTIAL, deserializedReadOptions.getFadvise());
+        GoogleCloudStorageReadOptions.Fadvise.RANDOM, deserializedReadOptions.getFadvise());
     assertFalse(deserializedReadOptions.isFastFailOnNotFoundEnabled());
     assertEquals(12345L, deserializedReadOptions.getMinRangeRequestSize());
   }