Re: [PR] GH-3044: HashJoin iterator construction no longer eagerly builds hash probe table. [jena]

[via GitHub]

Aklakan commented on code in PR #3047:
URL: https://github.com/apache/jena/pull/3047#discussion_r1983151248


##########
jena-arq/src/main/java/org/apache/jena/sparql/exec/RowSetOps.java:
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@@ -51,7 +51,7 @@ public static void consume(RowSet rowSet)
      * This operation consumes the RowSet.
      */
     public static long count(RowSet rowSet)
-    { return rowSet.rewindable().size(); }
+    { long c[] = {0}; rowSet.forEach(b -> ++c[0]); return c[0]; }

Review Comment:
   Behavior so far (IIRC):
   * For non-RowSetMem instances counting would create an intermediate 
in-memory copy.
   * The count for a RowSetMem instances would be the total number of bindings 
in the in-memory row set - rather than the number of remaining bindings.
   
   I added the method `RowSetStream.forEachRemaining` - the stack trace for 
`RowSetOps.count` using `rowSet.stream().count()` then becomes a delegate to 
the forEachRemaining method (with some stream creation overhead that should be 
neglectable for larger counts):
   
   
![image](https://github.com/user-attachments/assets/a9726dfa-4a7b-4dbc-b243-47ef2a18db43)
   



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