saffron.opt
Class AbstractConverter

java.lang.Object
  |
  +--saffron.rel.Rel
        |
        +--saffron.rel.SingleRel
              |
              +--saffron.rel.convert.Converter
                    |
                    +--saffron.opt.AbstractConverter

class AbstractConverter

extends Converter

Converts a relational expression to any given output convention.

Unlike most Converters, and 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

(package private) static class

AbstractConverter.ExpandConversionRule Rule which converts an AbstractConverter into a chain of converters from the source relation to the target calling convention.

Nested classes inherited from class saffron.rel.Rel

Field Summary

(package private) CallingConvention

outConvention

Fields inherited from class saffron.rel.convert.Converter

inConvention

Fields inherited from class saffron.rel.SingleRel

child

Fields inherited from class saffron.rel.Rel

cluster, digest, id, rowType

Constructor Summary

AbstractConverter(Cluster cluster, Rel rel, CallingConvention outConvention)

Method Summary

Object	clone()
Cost	computeSelfCost(Planner planner) Returns the cost of this plan (not including children).
void	explain(PlanWriter pw)
CallingConvention	getConvention() Returns a value from CallingConvention.

Methods inherited from class saffron.rel.convert.Converter

implement

Methods inherited from class saffron.rel.SingleRel

childrenAccept, deriveRowType, getInputs, replaceInput

Methods inherited from class saffron.rel.Rel

computeDigest, getChildExps, getCluster, getCorelVariable, getEnvironment, getId, getInput, getOrCreateCorelVariable, getParentEnv, getQualifier, getQuery, getRelTypeName, getRows, getRowType, getTable, getType, getVariablesStopped, implementExp, implementExps, implementFieldAccess, implementSelf, isAccessTo, isDistinct, onRegister, recomputeDigest, register, registerCorelVariable, setCorelVariable, toString

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

outConvention

final CallingConvention outConvention

Constructor Detail

AbstractConverter

public AbstractConverter(Cluster cluster,
                         Rel rel,
                         CallingConvention outConvention)

Method Detail

clone

public Object clone()

Specified by:

clone in class Rel

getConvention

public CallingConvention getConvention()

Description copied from class: Rel

Returns a value from CallingConvention.

Overrides:

getConvention in class Rel

computeSelfCost

public Cost computeSelfCost(Planner planner)

Description copied from class: Rel

Returns the cost of this plan (not including children). The base implementation throws an error; derived classes should override.

Overrides:

computeSelfCost in class Converter

explain

public void explain(PlanWriter pw)

Overrides:

explain in class SingleRel