org.apache.phoenix.expression

Class BaseExpression

java.lang.Object

org.apache.phoenix.expression.BaseExpression

All Implemented Interfaces:

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

Direct Known Subclasses:

BaseCompoundExpression, BaseSingleExpression, BaseTerminalExpression

public abstract class BaseExpression
extends Object
implements Expression

Base class for Expression hierarchy that provides common default implementations for most methods

Since:

0.1

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	BaseExpression.ExpressionComparabilityWrapper

Constructor Summary

Constructors

Constructor and Description
BaseExpression()

Method Summary

Modifier and Type	Method and Description
protected <T> List<T>	acceptChildren(ExpressionVisitor<T> visitor, Iterator<Expression> iterator)
static Expression	coerce(Expression lhs, Expression rhs, BaseExpression.ExpressionComparabilityWrapper wrapper, boolean rowKeyOrderOptimizable)
static Expression	coerce(Expression lhs, Expression rhs, CompareFilter.CompareOp op, boolean rowKeyOrderOptimizable) Coerce the RHS to match the LHS type, throwing if the types are incompatible.
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

Methods inherited from interface org.apache.phoenix.expression.Expression

accept, evaluate, getChildren

Methods inherited from interface org.apache.phoenix.schema.PDatum

getDataType

Constructor Detail

BaseExpression

public BaseExpression()

Method Detail

coerce

public static Expression coerce(Expression lhs,
                                Expression rhs,
                                CompareFilter.CompareOp op,
                                boolean rowKeyOrderOptimizable)
                         throws SQLException

Coerce the RHS to match the LHS type, throwing if the types are incompatible.

Parameters:

lhs - left hand side expression

rhs - right hand side expression

op - operator being used to compare the expressions, which can affect rounding we may need to do.

rowKeyOrderOptimizable -

Returns:

the newly coerced expression

Throws:

SQLException

coerce

public static Expression coerce(Expression lhs,
                                Expression rhs,
                                BaseExpression.ExpressionComparabilityWrapper wrapper,
                                boolean rowKeyOrderOptimizable)
                         throws SQLException

Throws:

SQLException

isNullable

public boolean isNullable()

Specified by:

isNullable in interface PDatum

Returns:

is this column nullable?

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

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

acceptChildren

protected final <T> List<T> acceptChildren(ExpressionVisitor<T> visitor,
                                           Iterator<Expression> iterator)

getDeterminism

public Determinism getDeterminism()

Specified by:

getDeterminism in interface Expression

Returns:

Determinism enum

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.

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: