org.apache.pig.newplan.logical.expression

Class DereferenceExpression

java.lang.Object

org.apache.pig.newplan.Operator

org.apache.pig.newplan.logical.expression.LogicalExpression

org.apache.pig.newplan.logical.expression.ColumnExpression

org.apache.pig.newplan.logical.expression.DereferenceExpression

All Implemented Interfaces:

java.io.Serializable

public class DereferenceExpression
extends ColumnExpression

get one or elements out of a tuple or a bag in case of Tuple( a#2:int, b#3:bag{ b_a#4:int, b_b#5:float }, c#6:int ) # 1 (the number after # represents the uid) Dereference ( 0 ) --> a:int - dereference of single column in a tuple gives the field Dereference ( 0,2 ) --> Tuple(a#2:int, c#6:int) #7 - dereference of more than one column gives a tuple Dereference ( 1 ) --> Dereference ( 1 ) --> b:bag{b_b#5:float}#8 - dereference of a bag gives a bag

See Also:

Serialized Form

Field Summary

Fields inherited from class org.apache.pig.newplan.logical.expression.LogicalExpression

fieldSchema, uidOnlyFieldSchema

Fields inherited from class org.apache.pig.newplan.Operator

annotations, hashPrime, location, name, plan

Constructor Summary

Constructors

Constructor and Description
DereferenceExpression(OperatorPlan plan)
DereferenceExpression(OperatorPlan plan, int colNum)
DereferenceExpression(OperatorPlan plan, java.util.List<java.lang.Integer> columnNums)

Method Summary

Modifier and Type	Method and Description
void	accept(PlanVisitor v) Accept a visitor at this node in the graph.
LogicalExpression	deepCopy(LogicalExpressionPlan lgExpPlan) Create the deep copy of this expression and add that into the passed LogicalExpressionPlan Return the copy of this expression with updated logical expression plan.
java.util.List<java.lang.Integer>	getBagColumns()
LogicalSchema.LogicalFieldSchema	getFieldSchema() Get the field schema for the output of this expression operator.
java.util.List<java.lang.Object>	getRawColumns()
LogicalExpression	getReferredExpression()
boolean	isEqual(Operator other) This is like a shallow equals comparison.
void	setBagColumns(java.util.List<java.lang.Integer> columns)
void	setRawColumns(java.util.List<java.lang.Object> cols)
java.lang.String	toString()

Methods inherited from class org.apache.pig.newplan.logical.expression.LogicalExpression

getNextUid, getType, hasFieldSchema, neverUseForRealSetFieldSchema, resetFieldSchema, resetNextUid, resetUid

Methods inherited from class org.apache.pig.newplan.Operator

annotate, getAnnotation, getLocation, getName, getPlan, removeAnnotation, setLocation, setPlan

Methods inherited from class java.lang.Object

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

Constructor Detail

DereferenceExpression

public DereferenceExpression(OperatorPlan plan)

DereferenceExpression

public DereferenceExpression(OperatorPlan plan,
                             int colNum)

DereferenceExpression

public DereferenceExpression(OperatorPlan plan,
                             java.util.List<java.lang.Integer> columnNums)

Method Detail

setRawColumns

public void setRawColumns(java.util.List<java.lang.Object> cols)

accept

public void accept(PlanVisitor v)
            throws FrontendException

Description copied from class: Operator

Accept a visitor at this node in the graph.

Specified by:

accept in class Operator

Parameters:

v - Visitor to accept.

Throws:

FrontendException

getBagColumns

public java.util.List<java.lang.Integer> getBagColumns()

setBagColumns

public void setBagColumns(java.util.List<java.lang.Integer> columns)

isEqual

public boolean isEqual(Operator other)
                throws FrontendException

Description copied from class: Operator

This is like a shallow equals comparison. It returns true if two operators have equivalent properties even if they are different objects. Here properties mean equivalent plan and equivalent name.

Specified by:

isEqual in class Operator

Returns:

true if two object have equivalent properties, else false

Throws:

FrontendException

getReferredExpression

public LogicalExpression getReferredExpression()
                                        throws FrontendException

Throws:

FrontendException

toString

public java.lang.String toString()

Overrides:

toString in class LogicalExpression

getFieldSchema

public LogicalSchema.LogicalFieldSchema getFieldSchema()
                                                throws FrontendException

Description copied from class: LogicalExpression

Get the field schema for the output of this expression operator. This does not merely return the field schema variable. If schema is not yet set, this will attempt to construct it. Therefore it is abstract since each operator will need to construct its field schema differently.

Specified by:

getFieldSchema in class LogicalExpression

Returns:

the FieldSchema

Throws:

FrontendException

deepCopy

public LogicalExpression deepCopy(LogicalExpressionPlan lgExpPlan)
                           throws FrontendException

Description copied from class: LogicalExpression

Create the deep copy of this expression and add that into the passed LogicalExpressionPlan Return the copy of this expression with updated logical expression plan.

Specified by:

deepCopy in class LogicalExpression

Parameters:

lgExpPlan - LogicalExpressionPlan in which this expression will be added.

Returns:

LogicalExpression with its own logical expression plan.

Throws:

FrontendException

getRawColumns

public java.util.List<java.lang.Object> getRawColumns()