saffron.ext
Class ExtentRel

java.lang.Object
  |
  +--saffron.rel.Rel
        |
        +--saffron.ext.ExtentRel

public class ExtentRel

extends Rel

ExtentRel represents all of the instances of a particular class (including subtypes).

It cannot be implemented as such, but can often be transformed into an expression which can. For example, in

JavaReflectConnection reflect;
 select
 from reflect.fields as field
 join reflect.classes as clazz
 on field.getDeclaringClass() == clazz &&
     clazz.getPackage().getName().equals("java.lang");

the field and clazz are constrained by join and filter conditions so that we can enumerate the required fields.

todo: Why is this not just a TableAccess?

See Also:

ExtentTable

Nested Class Summary

Nested classes inherited from class saffron.rel.Rel

Field Summary

private Table

table

Fields inherited from class saffron.rel.Rel

cluster, digest, id, rowType

Constructor Summary

ExtentRel(Cluster cluster, Type rowType, Table table)
Creates an ExtentRel.

Method Summary

Object	clone()
protected Type	deriveRowType()
void	explain(PlanWriter pw)
protected Table	getTable() If this relational expression represents an access to a table, returns that table, otherwise returns null.
boolean	isDistinct() Returns whether the same value will not come out twice.

Methods inherited from class saffron.rel.Rel

childrenAccept, computeDigest, computeSelfCost, getChildExps, getCluster, getConvention, getCorelVariable, getEnvironment, getId, getInput, getInputs, getOrCreateCorelVariable, getParentEnv, getQualifier, getQuery, getRelTypeName, getRows, getRowType, getType, getVariablesStopped, implement, implementExp, implementExps, implementFieldAccess, implementSelf, isAccessTo, onRegister, recomputeDigest, register, registerCorelVariable, replaceInput, setCorelVariable, toString

Methods inherited from class java.lang.Object

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

Field Detail

table

private Table table

Constructor Detail

ExtentRel

public ExtentRel(Cluster cluster,
                 Type rowType,
                 Table table)

Creates an ExtentRel.

Pre-condition:

rowType != null, table != null

Method Detail

clone

public Object clone()

Specified by:

clone in class Rel

explain

public void explain(PlanWriter pw)

Overrides:

explain in class Rel

deriveRowType

protected Type deriveRowType()

Specified by:

deriveRowType in class Rel

isDistinct

public boolean isDistinct()

Description copied from class: Rel

Returns whether the same value will not come out twice. Default value is false, derived classes should override.

Overrides:

isDistinct in class Rel

getTable

protected Table getTable()

Description copied from class: Rel

If this relational expression represents an access to a table, returns that table, otherwise returns null.

Overrides:

getTable in class Rel