org.eigenbase.relopt.volcano
Class AbstractConverter

java.lang.Object
  org.eigenbase.rel.AbstractRelNode
      org.eigenbase.rel.SingleRel
          org.eigenbase.rel.convert.ConverterRelImpl
              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

emptyArray

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

getChild

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

AbstractConverter

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

AbstractConverter

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

Method Detail

clone

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(...);
         clone.inheritTraitsFrom(this);
         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

Returns:

a clone of this RelNode

computeSelfCost

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

Overrides:

computeSelfCost in class ConverterRelImpl

explain

public void explain(RelOptPlanWriter pw)

Specified by:

explain in interface RelNode

Overrides:

explain in class SingleRel