Class OneRowRelBase

  extended by org.eigenbase.rel.AbstractRelNode
      extended by org.eigenbase.rel.OneRowRelBase
All Implemented Interfaces:
Cloneable, RelNode
Direct Known Subclasses:
IterOneRowRel, OneRowRel

public abstract class OneRowRelBase
extends AbstractRelNode

OneRowRelBase is an abstract base class for implementations of OneRowRel.

$Id: //open/dev/farrago/src/org/eigenbase/rel/ $
John V. Sichi

Field Summary
Fields inherited from class org.eigenbase.rel.AbstractRelNode
digest, id, nextId, rowType, traits
Fields inherited from interface org.eigenbase.rel.RelNode
Constructor Summary
protected OneRowRelBase(RelOptCluster cluster, RelTraitSet traits)
          Creates a OneRowRelBase with specific traits.
Method Summary
 OneRowRelBase clone()
          Clones this RelNode.
 RelOptCost computeSelfCost(RelOptPlanner planner)
          Returns the cost of this plan (not including children).
static RelDataType deriveOneRowType(RelDataTypeFactory typeFactory)
protected  RelDataType deriveRowType()
Methods inherited from class org.eigenbase.rel.AbstractRelNode
childrenAccept, cloneTraits, collectVariablesSet, collectVariablesUsed, computeDigest, explain, getChildExps, getCluster, getCollationList, getConvention, getCorrelVariable, getDescription, getDigest, getExpectedInputRowType, getId, getInput, getInputs, getOrCreateCorrelVariable, getQuery, getRelTypeName, getRows, getRowType, getTable, getTraits, getVariablesStopped, inheritTraitsFrom, isAccessTo, isDistinct, isValid, onRegister, recomputeDigest, register, registerCorrelVariable, replaceInput, setCorrelVariable, toString
Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail


protected OneRowRelBase(RelOptCluster cluster,
                        RelTraitSet traits)
Creates a OneRowRelBase with specific traits.

cluster - RelOptCluster this relational expression belongs to
traits - for this rel
Method Detail


public OneRowRelBase clone()
Description copied from interface: RelNode
Clones this RelNode.

Traits of the RelNode must be explicitly cloned, using AbstractRelNode.inheritTraitsFrom(AbstractRelNode), as the RelNode may have traits of which it has no knowledge. Example implementation:

     public MyRelNode clone()
         MyRelNode clone = new MyRelNode(...);
         return clone;
N.B.: This method must be overridden whenever an existing, concrete RelNode is extended. Otherwise, calling clone() will produce a differently typed RelNode, resulting in invalid or incorrect query plans.

Specified by:
clone in interface RelNode
Specified by:
clone in class AbstractRelNode
a clone of this RelNode


public RelOptCost computeSelfCost(RelOptPlanner planner)
Description copied from interface: RelNode
Returns the cost of this plan (not including children). The base implementation throws an error; derived classes should override.

NOTE jvs 29-Mar-2006: Don't call this method directly. Instead, use RelMetadataQuery.getNonCumulativeCost(org.eigenbase.rel.RelNode), which gives plugins a chance to override the rel's default ideas about cost.

Specified by:
computeSelfCost in interface RelNode
computeSelfCost in class AbstractRelNode


protected RelDataType deriveRowType()
deriveRowType in class AbstractRelNode


public static RelDataType deriveOneRowType(RelDataTypeFactory typeFactory)