Exclude partially cached .cfs file from SearchableSnapshotDirectoryStatsTests (#70006) (#70018)

Since #69861 CFS files read from FrozenIndexInput create 
dedicated frozen shared cache files when they are sliced. 
This does not play well with some tests that use the 
randomReadAndSlice to read files: this method can create 
overlapping slice/clone reads operations which makes it 
difficult to assert anything about CFS files with partial cache.

This commit prevent the tests to generate a .cfs file name 
when the partial cache is randomly picked up. As a follow 
up we should rework those test to make them more realistic 
with the new behavior.

Closes #70000

Author: tlrx

test/framework/src/main/java/org/elasticsearch/common/lucene/store/ESIndexInputTestCase.java

@@ -72,7 +72,8 @@ protected byte[] randomReadAndSlice(IndexInput indexInput, int length) throws IO
                 case 3:
                     // Read using slice
                     len = randomIntBetween(1, length - readPos);
-                    IndexInput slice = indexInput.slice(randomAlphaOfLength(10) + randomFileExtension(), readPos, len);
+                    final String sliceExtension = randomValueOtherThan(".cfs", ESIndexInputTestCase::randomFileExtension);
+                    IndexInput slice = indexInput.slice(randomAlphaOfLength(10) + sliceExtension, readPos, len);
                     temp = randomReadAndSlice(slice, len);
                     // assert that position in the original input didn't change
                     assertEquals(readPos, indexInput.getFilePointer());
@@ -121,7 +122,8 @@ protected void doRun() throws Exception {
                                     clone = indexInput.clone();
                                 } else {
                                     final int sliceEnd = between(readEnd, length);
-                                    clone = indexInput.slice("slice" + randomAlphaOfLength(10) + randomFileExtension(), 0L, sliceEnd);
+                                    final String sliceExtension = randomValueOtherThan(".cfs", ESIndexInputTestCase::randomFileExtension);
+                                    clone = indexInput.slice("slice" + randomAlphaOfLength(10) + sliceExtension, 0L, sliceEnd);
                                 }
                                 startLatch.countDown();
                                 startLatch.await();

x-pack/plugin/searchable-snapshots/src/test/java/org/elasticsearch/index/store/SearchableSnapshotDirectoryStatsTests.java

@@ -19,6 +19,7 @@
 import org.elasticsearch.common.TriConsumer;
 import org.elasticsearch.common.UUIDs;
 import org.elasticsearch.common.blobstore.BlobContainer;
+import org.elasticsearch.common.lucene.store.ESIndexInputTestCase;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.unit.ByteSizeUnit;
 import org.elasticsearch.common.unit.ByteSizeValue;
@@ -605,8 +606,14 @@ private void executeTestCase(
         final TriConsumer<String, byte[], SearchableSnapshotDirectory> test
     ) throws Exception {
 
+        final String fileName;
+        if (SearchableSnapshots.SNAPSHOT_PARTIAL_SETTING.get(indexSettings)) {
+            fileName = randomAlphaOfLength(10) + randomValueOtherThan(".cfs", ESIndexInputTestCase::randomFileExtension);
+        } else {
+            fileName = randomAlphaOfLength(10) + randomFileExtension();
+        }
+
         final byte[] fileContent = randomByteArrayOfLength(randomIntBetween(10, MAX_FILE_LENGTH));
-        final String fileName = randomAlphaOfLength(10) + randomFileExtension();
         final SnapshotId snapshotId = new SnapshotId("_name", "_uuid");
         final IndexId indexId = new IndexId("_name", "_uuid");
         final ShardId shardId = new ShardId("_name", "_uuid", 0);