saffron.rel
Class Filter

java.lang.Object
  |
  +--saffron.rel.Rel
        |
        +--saffron.rel.SingleRel
              |
              +--saffron.rel.Filter

Direct Known Subclasses:

JavaFilter, PlanFilter

public class Filter

extends SingleRel

A Filter is a relational expression which iterates over its input, and returns elements for which condition evaluates to true.

Nested Class Summary

private static class	Filter.ConvertToJavaRule
private static class	Filter.ConvertToPlanRule

Nested classes inherited from class saffron.rel.Rel

Field Summary

Expression

condition

Fields inherited from class saffron.rel.SingleRel

child

Fields inherited from class saffron.rel.Rel

cluster, digest, emptyArray, id, nextId, rowType

Constructor Summary

Filter(Cluster cluster, Rel child, Expression condition)
Creates a filter.

Method Summary

Object	clone()
Cost	computeSelfCost(Planner planner) Returns the cost of this plan (not including children).
void	explain(PlanWriter pw)
Expression[]	getChildExps() Returns an array of this Rel's child expressions (not including the inputs returned by SingleRel.getInputs().
static void	register(Planner planner) See Rel.register(saffron.Planner).

Methods inherited from class saffron.rel.SingleRel

childrenAccept, deriveRowType, getInputs, replaceInput

Methods inherited from class saffron.rel.Rel

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

Methods inherited from class java.lang.Object

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

Field Detail

condition

public Expression condition

Constructor Detail

Filter

public Filter(Cluster cluster,
              Rel child,
              Expression condition)

Creates a filter.

Parameters:

cluster - Cluster this relational expression belongs to

child - input relational expression

condition - boolean expression which determines whether a row is allowed to pass

Method Detail

clone

public Object clone()

Specified by:

clone in class Rel

getChildExps

public Expression[] getChildExps()

Description copied from class: Rel

Returns an array of this Rel's child expressions (not including the inputs returned by Rel.getInputs(). If there are no child expressions, returns an empty array, not null.

Overrides:

getChildExps in class Rel

explain

public void explain(PlanWriter pw)

Overrides:

explain in class SingleRel

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 Rel

register

public static void register(Planner planner)

See Rel.register(saffron.Planner).