org.vanilladb.core.sql.predicate

Interface Expression

All Known Implementing Classes:

BinaryArithmeticExpression, ConstantExpression, FieldNameExpression

public interface Expression

A SQL expression.

Method Summary

Modifier and Type	Method and Description
Constant	asConstant() Returns the constant corresponding to a constant expression.
String	asFieldName() Returns the field name corresponding to a field name expression.
Constant	evaluate(Record rec) Evaluates the expression with respect to the specified record.
boolean	isApplicableTo(Schema sch) Determines if all of the fields mentioned in this expression are contained in the specified schema.
boolean	isConstant() Returns true if the expression is a constant.
boolean	isFieldName() Returns true if the expression is a field reference.

Method Detail

isConstant

boolean isConstant()

Returns true if the expression is a constant.

Returns:

true if the expression is a constant

isFieldName

boolean isFieldName()

Returns true if the expression is a field reference.

Returns:

true if the expression denotes a field

asConstant

Constant asConstant()

Returns the constant corresponding to a constant expression. Throws an exception if this expression does not denote a constant.

Returns:

the expression as a constant

asFieldName

String asFieldName()

Returns the field name corresponding to a field name expression. Throws an exception if this expression does not denote a field.

Returns:

the expression as a field name

evaluate

Constant evaluate(Record rec)

Evaluates the expression with respect to the specified record.

Parameters:

rec - the record

Returns:

the value of the expression, as a constant

isApplicableTo

boolean isApplicableTo(Schema sch)

Determines if all of the fields mentioned in this expression are contained in the specified schema.

Parameters:

sch - the schema

Returns:

true if all fields in the expression are in the schema