[fix][core] Optimize decorrelate

Author: guojn1

core/src/main/java/org/apache/calcite/sql2rel/RelDecorrelator.java

@@ -706,16 +706,6 @@ private static void shiftMapping(Map<Integer, Integer> mapping, int startIndex,
   public @Nullable Frame getInvoke(RelNode r, boolean isCorVarDefined, @Nullable RelNode parent) {
     final Frame frame = dispatcher.invoke(r, isCorVarDefined);
     currentRel = parent;
-    if (frame != null && isCorVarDefined && r instanceof Sort) {
-      final Sort sort = (Sort) r;
-      // Can not decorrelate if the sort has per-correlate-key attributes like
-      // offset or fetch limit, because these attributes scope would change to
-      // global after decorrelation. They should take effect within the scope
-      // of the correlation key actually.
-      if (sort.offset != null || sort.fetch != null) {
-        return null;
-      }
-    }
     if (frame != null) {
       map.put(r, frame);
     }