```
public class Holder
extends MutableSingleRel
```
Implementation of MutableRel whose only purpose is to have a child. Used as the root of a tree.

Field Summary
- Fields inherited from class org.apache.calcite.rel.mutable.MutableSingleRel
  input
- Fields inherited from class org.apache.calcite.rel.mutable.MutableRel
  cluster, ordinalInParent, PAIRWISE_STRING_EQUIVALENCE, parent, rowType, STRING_EQUIVALENCE, type

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`MutableRel`	`clone()`
`java.lang.StringBuilder`	`digest(java.lang.StringBuilder buf)`
`static Holder`	`of(MutableRel input)`	Creates a Holder.

Methods inherited from class org.apache.calcite.rel.mutable.MutableSingleRel
childrenAccept, getInput, getInputs, setInput

Methods inherited from class org.apache.calcite.rel.mutable.MutableRel
deep, getParent, replaceInParent, toString

Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

private Holder(RelDataType rowType,
               MutableRel input)

Class Holder