saffron.rel.plan
Class PlanNestedLoopJoin

java.lang.Object
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  +--saffron.rel.Rel
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        +--saffron.rel.Join
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              +--saffron.rel.plan.PlanNestedLoopJoin

public class PlanNestedLoopJoin

extends Join

PlanNestedLoopJoin implements Join using the nested-loop algorithm, with output as a Plan.

Nested-loops are the simplest implementation of a join: for each row from the left hand side, get each row from the right hand side, apply the condition, and return a joined row if the condition evaluates true.

A join isn't a relational expression as such. The output of a join plan is an array of all of the objects which went into it. So, for example, the output of emp join (dept join division) contains 3 objects.

Nested Class Summary

Nested classes inherited from class saffron.rel.Join

Join.JoinType

Nested classes inherited from class saffron.rel.Rel

Field Summary

Fields inherited from class saffron.rel.Join

condition, joinType, left, right, variablesStopped

Fields inherited from class saffron.rel.Rel

cluster, digest, id, rowType

Constructor Summary

PlanNestedLoopJoin(Cluster cluster, Rel left, Rel right, Expression condition, int joinType, Set variablesStopped)

Method Summary

Object	clone()
Cost	computeSelfCost(Planner planner) Returns the cost of this plan (not including children).
CallingConvention	getConvention() Returns a value from CallingConvention.
Object	implement(Implementor implementor, int ordinal) Create a plan for this expression according to a calling convention.

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

Constructor Detail

PlanNestedLoopJoin

public PlanNestedLoopJoin(Cluster cluster,
                          Rel left,
                          Rel right,
                          Expression condition,
                          int joinType,
                          Set variablesStopped)

Method Detail

clone

public Object clone()

Overrides:

clone in class Join

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

getConvention

public CallingConvention getConvention()

Description copied from class: Rel

Returns a value from CallingConvention.

Overrides:

getConvention in class Rel

implement

public Object implement(Implementor implementor,
                        int ordinal)

Description copied from class: Rel

Create a plan for this expression according to a calling convention.

Overrides:

implement in class Rel

Parameters:

implementor - implementor

ordinal - indicates our position in the pre-, in- and postfix walk over the tree; ordinal is -1 when called from the parent, and i when called from the i^th child.