Only use direct IO in searches

Author: thecoop

server/src/main/java/org/elasticsearch/index/codec/vectors/es818/ES818FlatVectorsReader.java

@@ -119,7 +119,7 @@ private static IndexInput openDataInput(
         IOContext context
     ) throws IOException {
         String fileName = IndexFileNames.segmentFileName(state.segmentInfo.name, state.segmentSuffix, fileExtension);
-        IndexInput in = state.directory instanceof DirectIOIndexInputSupplier did
+        IndexInput in = context.context() == IOContext.Context.DEFAULT && state.directory instanceof DirectIOIndexInputSupplier did
             ? did.openInputDirect(fileName, context)
             : state.directory.openInput(fileName, context);
         boolean success = false;