org.eigenbase.relopt
Class RelOptCostImpl

java.lang.Object
  org.eigenbase.relopt.RelOptCostImpl

All Implemented Interfaces:

RelOptCost

public class RelOptCostImpl
extends Object
implements RelOptCost

RelOptCostImpl provides a default implementation for the RelOptCost interface. It it defined in terms of a single scalar quantity; somewhat arbitrarily, it returns this scalar for rows processed and zero for both CPU and I/O.

Version:

$Id: //open/dev/farrago/src/org/eigenbase/relopt/RelOptCostImpl.java#9 $

Author:

John V. Sichi

Field Summary

private double

value

Constructor Summary

RelOptCostImpl(double value)

Method Summary

double	divideBy(RelOptCost cost) Computes the ratio between this cost and another cost.
boolean	equals(RelOptCost other) Compares this to another cost.
double	getCpu()
double	getIo()
double	getRows()
boolean	isEqWithEpsilon(RelOptCost other) Compares this to another cost, allowing for slight roundoff errors.
boolean	isInfinite()
boolean	isLe(RelOptCost other) Compares this to another cost.
boolean	isLt(RelOptCost other) Compares this to another cost.
RelOptCost	minus(RelOptCost other) Subtracts another cost from this.
RelOptCost	multiplyBy(double factor) Multiplies this cost by a scalar factor.
RelOptCost	plus(RelOptCost other) Adds another cost to this.
String	toString() Forces implementations to override Object.toString() and provide a good cost rendering to use during tracing.

Methods inherited from class java.lang.Object

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

Field Detail

value

private final double value

Constructor Detail

RelOptCostImpl

public RelOptCostImpl(double value)

Method Detail

getRows

public double getRows()

Specified by:

getRows in interface RelOptCost

Returns:

number of rows processed; this should not be confused with the row count produced by a relational expression (RelNode.getRows())

getIo

public double getIo()

Specified by:

getIo in interface RelOptCost

Returns:

usage of I/O resources

getCpu

public double getCpu()

Specified by:

getCpu in interface RelOptCost

Returns:

usage of CPU resources

isInfinite

public boolean isInfinite()

Specified by:

isInfinite in interface RelOptCost

Returns:

true iff this cost represents an expression that hasn't actually been implemented (e.g. a pure relational algebra expression) or can't actually be implemented, e.g. a transfer of data between two disconnected sites

isLe

public boolean isLe(RelOptCost other)

Description copied from interface: RelOptCost

Compares this to another cost.

Specified by:

isLe in interface RelOptCost

Parameters:

other - another cost

Returns:

true iff this is less than or equal to other cost

isLt

public boolean isLt(RelOptCost other)

Description copied from interface: RelOptCost

Compares this to another cost.

Specified by:

isLt in interface RelOptCost

Parameters:

other - another cost

Returns:

true iff this is strictly less than other cost

equals

public boolean equals(RelOptCost other)

Description copied from interface: RelOptCost

Compares this to another cost.

Specified by:

equals in interface RelOptCost

Parameters:

other - another cost

Returns:

true iff this is exactly equal to other cost

isEqWithEpsilon

public boolean isEqWithEpsilon(RelOptCost other)

Description copied from interface: RelOptCost

Compares this to another cost, allowing for slight roundoff errors.

Specified by:

isEqWithEpsilon in interface RelOptCost

Parameters:

other - another cost

Returns:

true iff this is the same as the other cost within a roundoff margin of error

minus

public RelOptCost minus(RelOptCost other)

Description copied from interface: RelOptCost

Subtracts another cost from this.

Specified by:

minus in interface RelOptCost

Parameters:

other - another cost

Returns:

difference between this and other cost

plus

public RelOptCost plus(RelOptCost other)

Description copied from interface: RelOptCost

Adds another cost to this.

Specified by:

plus in interface RelOptCost

Parameters:

other - another cost

Returns:

sum of this and other cost

multiplyBy

public RelOptCost multiplyBy(double factor)

Description copied from interface: RelOptCost

Multiplies this cost by a scalar factor.

Specified by:

multiplyBy in interface RelOptCost

Parameters:

factor - scalar factor

Returns:

scalar product of this and factor

divideBy

public double divideBy(RelOptCost cost)

Description copied from interface: RelOptCost

Computes the ratio between this cost and another cost.

divideBy is the inverse of RelOptCost.multiplyBy(double). For any finite, non-zero cost and factor f, cost.divideBy(cost.multiplyBy(f)) yields 1 / f.

Specified by:

divideBy in interface RelOptCost

Parameters:

cost - Other cost

Returns:

Ratio between costs

toString

public String toString()

Description copied from interface: RelOptCost

Forces implementations to override Object.toString() and provide a good cost rendering to use during tracing.

Specified by:

toString in interface RelOptCost

Overrides:

toString in class Object