org.apache.phoenix.expression

Class DelegateExpression

java.lang.Object

org.apache.phoenix.expression.DelegateExpression

All Implemented Interfaces:

org.apache.hadoop.io.Writable, Expression, PDatum

public class DelegateExpression
extends Object
implements Expression

Constructor Summary

Constructors

Constructor and Description
DelegateExpression(Expression delegate)

Method Summary

Methods

Modifier and Type	Method and Description
<T> T	accept(ExpressionVisitor<T> visitor) Means of traversing expression tree through visitor.
boolean	evaluate(Tuple tuple, ImmutableBytesWritable ptr) Access the value by setting a pointer to it (as opposed to making a copy of it which can be expensive)
List<Expression>	getChildren()
PDataType	getDataType()
Determinism	getDeterminism()
Integer	getMaxLength()
Integer	getScale()
SortOrder	getSortOrder()
boolean	isNullable()
boolean	isStateless()
void	readFields(DataInput input)
boolean	requiresFinalEvaluation() Determines if an evaluate is required after partial evaluation is run.
void	reset() Resets the state of a expression back to its initial state and enables the expession to be evaluated incrementally (which occurs during filter evaluation where we see one key value at a time; it's possible to evaluate immediately rather than wait until all key values have been seen).
void	write(DataOutput output)

Methods inherited from class java.lang.Object

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

Constructor Detail

DelegateExpression

public DelegateExpression(Expression delegate)

Method Detail

isNullable

public boolean isNullable()

Specified by:

isNullable in interface PDatum

Returns:

is this column nullable?

getDataType

public PDataType getDataType()

Specified by:

getDataType in interface PDatum

Returns:

data type of the column

getMaxLength

public Integer getMaxLength()

Specified by:

getMaxLength in interface PDatum

Returns:

the actual length of the column. For decimal, it would be its precision. For char or varchar, it would be the maximum length as specified during schema definition.

getScale

public Integer getScale()

Specified by:

getScale in interface PDatum

Returns:

scale of a decimal number.

getSortOrder

public SortOrder getSortOrder()

Specified by:

getSortOrder in interface PDatum

Returns:

The SortOrder for this column, never null

readFields

public void readFields(DataInput input)
                throws IOException

Specified by:

readFields in interface org.apache.hadoop.io.Writable

Throws:

IOException

write

public void write(DataOutput output)
           throws IOException

Specified by:

write in interface org.apache.hadoop.io.Writable

Throws:

IOException

evaluate

public boolean evaluate(Tuple tuple,
               ImmutableBytesWritable ptr)

Description copied from interface: Expression

Access the value by setting a pointer to it (as opposed to making a copy of it which can be expensive)

Specified by:

evaluate in interface Expression

Parameters:

tuple - Single row result during scan iteration

ptr - Pointer to byte value being accessed

Returns:

true if the expression could be evaluated (i.e. ptr was set) and false otherwise

accept

public <T> T accept(ExpressionVisitor<T> visitor)

Description copied from interface: Expression

Means of traversing expression tree through visitor.

Specified by:

accept in interface Expression

getChildren

public List<Expression> getChildren()

Specified by:

getChildren in interface Expression

Returns:

the child expressions

reset

public void reset()

Description copied from interface: Expression

Resets the state of a expression back to its initial state and enables the expession to be evaluated incrementally (which occurs during filter evaluation where we see one key value at a time; it's possible to evaluate immediately rather than wait until all key values have been seen). Note that when evaluating incrementally, you must call this method before processing a new row.

Specified by:

reset in interface Expression

isStateless

public boolean isStateless()

Specified by:

isStateless in interface Expression

Returns:

true if the expression can be evaluated on the client side with out server state. If a sequence is involved, you still need a Tuple from a SequenceResultIterator, but otherwise the Tuple may be null.

getDeterminism

public Determinism getDeterminism()

Specified by:

getDeterminism in interface Expression

Returns:

Determinism enum

requiresFinalEvaluation

public boolean requiresFinalEvaluation()

Description copied from interface: Expression

Determines if an evaluate is required after partial evaluation is run. For example, in the case of an IS NULL expression, we only know we can return TRUE after all KeyValues have been seen while an expression is used in the context of a filter.

Specified by:

requiresFinalEvaluation in interface Expression

Returns: