thecoop commented on code in PR #14510:
URL: https://github.com/apache/lucene/pull/14510#discussion_r2075540345


##########
lucene/core/src/java/org/apache/lucene/store/MMapDirectory.java:
##########
@@ -277,6 +277,32 @@ public final long getMaxChunkSize() {
     return 1L << chunkSizePower;
   }
 
+  public static ReadAdvice toReadAdvice(IOContext context) {
+    if (context.context() == IOContext.Context.MERGE
+        || context.context() == IOContext.Context.FLUSH) {
+      return ReadAdvice.SEQUENTIAL;
+    }
+
+    if (context.hints().contains(DataAccessHint.RANDOM)) {
+      return ReadAdvice.RANDOM;
+    }
+    if (context.hints().contains(DataAccessHint.SEQUENTIAL)) {
+      return ReadAdvice.SEQUENTIAL;
+    }
+
+    if (context.hints().contains(FileTypeHint.DATA)
+        || context.hints().contains(FileTypeHint.INDEX)) {
+      return ReadAdvice.NORMAL;
+    }
+    // Postings have a forward-only access pattern, so pass ReadAdvice.NORMAL 
to perform
+    // readahead.
+    if (context.hints().contains(FileDataHint.POSTINGS)) {
+      return ReadAdvice.NORMAL;
+    }

Review Comment:
   I've taken another look at this, and reduced MMapDirectory down to only 
check `DataAccessHint` and `FileTypeHint`, without changing behavior.



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