saffron.rel
Class Project

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

Direct Known Subclasses:

JavaProject, PlanProject

public class Project

extends SingleRel

Project is a relational expression which computes a set of 'select expressions' from its input relational expression.

The result is usually 'boxed' as a record with one named field for each column; if there is precisely one expression, the result may be 'unboxed', and consist of the raw value type.

Nested Class Summary

private static class	Project.ConvertToJavaRule Converts a Project to Java calling convention.
private static class	Project.ConvertToPlanRule Converts a Project to plan calling convention.
static interface	Project.Flags

Nested classes inherited from class saffron.rel.Rel

Field Summary

protected Expression[]	exps
protected String[]	fieldNames
protected int	flags Values defined in Project.Flags.

Fields inherited from class saffron.rel.SingleRel

child

Fields inherited from class saffron.rel.Rel

cluster, digest, emptyArray, id, nextId, rowType

Constructor Summary

Project(Cluster cluster, Rel child, Expression[] exps, String[] fieldNames, int flags)
Creates a Project.

Method Summary

Object	clone()
Cost	computeSelfCost(Planner planner) Returns the cost of this plan (not including children).
protected Type	deriveRowType()
void	explain(PlanWriter pw)
Expression[]	getChildExps() Returns an array of this Rel's child expressions (not including the inputs returned by SingleRel.getInputs().
int	getFlags()
Rel	implementFieldAccess(Implementor implementor, String fieldName) Burrows into a synthetic record and returns the underlying relation which provides the field called fieldName.
boolean	isBoxed()
static void	register(Planner planner) See Rel.register(saffron.Planner).

Methods inherited from class saffron.rel.SingleRel

childrenAccept, 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, 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

exps

protected Expression[] exps

fieldNames

protected String[] fieldNames

flags

protected int flags

Values defined in Project.Flags.

Constructor Detail

Project

public Project(Cluster cluster,
               Rel child,
               Expression[] exps,
               String[] fieldNames,
               int flags)

Creates a Project.

Parameters:

cluster - Cluster this relational expression belongs to

child - input relational expression

exps - set of expressions for the input columns

fieldNames - aliases of the expressions

flags - values as in Project.Flags

Method Detail

clone

public Object clone()

Specified by:

clone in class Rel

getFlags

public int getFlags()

isBoxed

public boolean isBoxed()

deriveRowType

protected Type deriveRowType()

Overrides:

deriveRowType in class SingleRel

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

register

public static void register(Planner planner)

See Rel.register(saffron.Planner).

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

implementFieldAccess

public Rel implementFieldAccess(Implementor implementor,
                                String fieldName)

Description copied from class: Rel

Burrows into a synthetic record and returns the underlying relation which provides the field called fieldName.

Overrides:

implementFieldAccess in class Rel