RelOptCost (Calcite Core 1.2.0-incubating API)

All Known Implementing Classes:

RelOptCostImpl
```
public interface RelOptCost
```
RelOptCost defines an interface for optimizer cost in terms of number of rows processed, CPU cost, and I/O cost. Optimizer implementations may use all of this information, or selectively ignore portions of it. The specific units for all of these quantities are rather vague; most relational expressions provide a default cost calculation, but optimizers can override this by plugging in their own cost models with well-defined meanings for each unit. Optimizers which supply their own cost models may also extend this interface with additional cost metrics such as memory usage.

Method Summary

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

- Method Detail
  - getRows
```
double getRows()
```
    Returns:
    number of rows processed; this should not be confused with the row count produced by a relational expression (RelNode.getRows())
  - getCpu
```
double getCpu()
```
    Returns:
    usage of CPU resources
  - getIo
```
double getIo()
```
    Returns:
    usage of I/O resources
  - isInfinite
```
boolean isInfinite()
```
    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
  - equals
```
boolean equals(RelOptCost cost)
```
    Compares this to another cost.
    
    Parameters:
    cost - another cost
    
    Returns:
    true iff this is exactly equal to other cost
  - isEqWithEpsilon
```
boolean isEqWithEpsilon(RelOptCost cost)
```
    Compares this to another cost, allowing for slight roundoff errors.
    
    Parameters:
    cost - another cost
    
    Returns:
    true iff this is the same as the other cost within a roundoff margin of error
  - isLe
```
boolean isLe(RelOptCost cost)
```
    Compares this to another cost.
    
    Parameters:
    cost - another cost
    
    Returns:
    true iff this is less than or equal to other cost
  - isLt
```
boolean isLt(RelOptCost cost)
```
    Compares this to another cost.
    
    Parameters:
    cost - another cost
    
    Returns:
    true iff this is strictly less than other cost
  - plus
```
RelOptCost plus(RelOptCost cost)
```
    Adds another cost to this.
    
    Parameters:
    cost - another cost
    
    Returns:
    sum of this and other cost
  - minus
```
RelOptCost minus(RelOptCost cost)
```
    Subtracts another cost from this.
    
    Parameters:
    cost - another cost
    
    Returns:
    difference between this and other cost
  - multiplyBy
```
RelOptCost multiplyBy(double factor)
```
    Multiplies this cost by a scalar factor.
    
    Parameters:
    factor - scalar factor
    
    Returns:
    scalar product of this and factor
  - divideBy
```
double divideBy(RelOptCost cost)
```
    Computes the ratio between this cost and another cost.
    divideBy is the inverse of multiplyBy(double). For any finite, non-zero cost and factor f, cost.divideBy(cost.multiplyBy(f)) yields 1 / f.
    
    Parameters:
    cost - Other cost
    
    Returns:
    Ratio between costs
  - toString
```
String toString()
```
    Forces implementations to override Object.toString() and provide a good cost rendering to use during tracing.
    
    Overrides:
    
    toString in class Object

Interface RelOptCost

Method Summary

Method Detail

getRows

getCpu

getIo

isInfinite

equals

isEqWithEpsilon

isLe

isLt

plus

minus

multiplyBy

divideBy

toString