[GitHub] [calcite] jinxing64 opened a new pull request #1330: [CALCITE-3211] MutableRel returned from MutableRels::toMutables may lose reference to parent

[GitBox <gi...@apache.org>]

jinxing64 opened a new pull request #1330: [CALCITE-3211] MutableRel returned from MutableRels::toMutables may lose reference to parent
URL: https://github.com/apache/calcite/pull/1330
 
 
   Current implementation of MutableRels::toMutables is as below:
   ```
     private static List<MutableRel> toMutables(List<RelNode> nodes) {
       return Lists.transform(nodes, MutableRels::toMutable);
     }
   ```
   Thus every time we get from the result list, a new `MutableRel` will be created:
   ```
     private static class TransformingRandomAccessList<F, T> extends AbstractList<T>
         implements RandomAccess, Serializable {
       final List<F> fromList;
       final Function<? super F, ? extends T> function;
   
       TransformingRandomAccessList(List<F> fromList, Function<? super F, ? extends T> function) {
         this.fromList = checkNotNull(fromList);
         this.function = checkNotNull(function);
       }
   
       @Override
       public T get(int index) {
         return function.apply(fromList.get(index));
       }
   ......
   ```
   As a result, the parent information will be lost.
   This PR propose to refine the implementation of `MutableRels::toMutables` and avoid creating a new `MutableRel` every time when we get the object.

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