Class AbstractConverter

  extended by org.eigenbase.rel.AbstractRelNode
      extended by org.eigenbase.rel.SingleRel
          extended by org.eigenbase.rel.convert.ConverterRelImpl
              extended by org.eigenbase.relopt.volcano.AbstractConverter
All Implemented Interfaces:
Cloneable, ConverterRel, RelNode

public class AbstractConverter
extends ConverterRelImpl

Converts a relational expression to any given output convention.

Unlike most ConverterRels, an abstract converter is always abstract. You would typically create an AbstractConverter when it is necessary to transform a relational expression immediately; later, rules will transform it into relational expressions which can be implemented.

If an abstract converter cannot be satisfied immediately (because the source subset is abstract), the set is flagged, so this converter will be expanded as soon as a non-abstract relexp is added to the set.

Nested Class Summary
static class AbstractConverter.ExpandConversionRule
          Rule which converts an AbstractConverter into a chain of converters from the source relation to the target traits.
Field Summary
Fields inherited from class org.eigenbase.rel.convert.ConverterRelImpl
inTraits, traitDef
Fields inherited from class org.eigenbase.rel.AbstractRelNode
digest, id, rowType, traits
Fields inherited from interface org.eigenbase.rel.RelNode
Constructor Summary
AbstractConverter(RelOptCluster cluster, RelNode rel, CallingConvention outConvention)
AbstractConverter(RelOptCluster cluster, RelNode rel, RelTraitDef traitDef, RelTraitSet traits)
Method Summary
 AbstractConverter clone()
          Clones this RelNode.
 RelOptCost computeSelfCost(RelOptPlanner planner)
          Returns the cost of this plan (not including children).
 void explain(RelOptPlanWriter pw)
Methods inherited from class org.eigenbase.rel.convert.ConverterRelImpl
cannotImplement, convertTraits, getInputConvention, getInputTraits, getTraitDef, isDistinct
Methods inherited from class org.eigenbase.rel.SingleRel
childrenAccept, deriveRowType, getChild, getInputs, getRows, replaceInput
Methods inherited from class org.eigenbase.rel.AbstractRelNode
cloneTraits, collectVariablesSet, collectVariablesUsed, computeDigest, getChildExps, getCluster, getCollationList, getConvention, getCorrelVariable, getDescription, getDigest, getExpectedInputRowType, getId, getInput, getOrCreateCorrelVariable, getQuery, getRelTypeName, getRowType, getTable, getTraits, getVariablesStopped, inheritTraitsFrom, isAccessTo, isValid, onRegister, recomputeDigest, register, registerCorrelVariable, setCorrelVariable, toString
Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Methods inherited from interface org.eigenbase.rel.convert.ConverterRel
Methods inherited from interface org.eigenbase.rel.RelNode
childrenAccept, collectVariablesSet, collectVariablesUsed, getChildExps, getCluster, getCollationList, getConvention, getCorrelVariable, getDescription, getDigest, getExpectedInputRowType, getId, getInput, getInputs, getOrCreateCorrelVariable, getQuery, getRelTypeName, getRows, getRowType, getTable, getTraits, getVariablesStopped, isAccessTo, isValid, onRegister, recomputeDigest, registerCorrelVariable, replaceInput, setCorrelVariable

Constructor Detail


public AbstractConverter(RelOptCluster cluster,
                         RelNode rel,
                         CallingConvention outConvention)


public AbstractConverter(RelOptCluster cluster,
                         RelNode rel,
                         RelTraitDef traitDef,
                         RelTraitSet traits)
Method Detail


public AbstractConverter 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 ConverterRelImpl


public void explain(RelOptPlanWriter pw)
Specified by:
explain in interface RelNode
explain in class SingleRel