saffron.rel
Class Correlator

java.lang.Object
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  +--saffron.rel.Rel
        |
        +--saffron.rel.Join
              |
              +--saffron.rel.Correlator

public class Correlator

extends Join

A Correlator behaves like a kind of Join, but works by setting variables in its environment and restarting its right-hand input. It is used to represent a correlated query; one implementation option is to de-correlate the expression.

Since:

23 September, 2001

Version:

$Id: //open/saffron/src/main/saffron/rel/Correlator.java#3 $

Author:

jhyde

Nested Class Summary

Nested classes inherited from class saffron.rel.Join

Join.JoinType

Nested classes inherited from class saffron.rel.Rel

Field Summary

(package private) Expression[]

correlations

Fields inherited from class saffron.rel.Join

condition, joinType, left, right, variablesStopped

Fields inherited from class saffron.rel.Rel

cluster, digest, emptyArray, id, nextId, rowType

Constructor Summary

(package private)

Correlator(Cluster cluster, Rel left, Rel right, int joinType, Expression[] correlations) Creates a Correlator.

Method Summary

Object

clone()

Methods inherited from class saffron.rel.Join

childrenAccept, deriveRowType, explain, getChildExps, getCondition, getInputs, getJoinType, getLeft, getRight, getVariablesStopped, register, registerStoppedVariable, replaceInput, setVariablesStopped, switchJoinType

Methods inherited from class saffron.rel.Rel

computeDigest, computeSelfCost, getCluster, getConvention, getCorelVariable, getEnvironment, getId, getInput, getOrCreateCorelVariable, getParentEnv, getQualifier, getQuery, getRelTypeName, getRows, getRowType, getTable, getType, 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

correlations

Expression[] correlations

Constructor Detail

Correlator

Correlator(Cluster cluster,
           Rel left,
           Rel right,
           int joinType,
           Expression[] correlations)

Creates a Correlator.

Parameters:

cluster - Cluster this relational expression belongs to

left - left input relational expression

right - right input relational expression

joinType - join type (see Join.joinType)

correlations - set of expressions to set as variables each time a row arrives from the left input

Method Detail

clone

public Object clone()

Overrides:

clone in class Join