org.vanilladb.core.sql.predicate

Class Predicate

java.lang.Object

org.vanilladb.core.sql.predicate.Predicate

public class Predicate
extends Object

A Boolean combination of terms.

Constructor Summary

Constructors

Constructor and Description
Predicate() Creates an empty predicate, corresponding to "true".
Predicate(Term t) Creates a predicate containing a single term.

Method Summary

Modifier and Type	Method and Description
void	conjunctWith(Term t) Modifies the predicate to be the conjunction of itself and the specified term.
ConstantRange	constantRange(String fldName) Determines if the specified field is constrained by a constant range in this predicate.
boolean	isSatisfied(Record rec) Returns true if this predicate evaluates to true with respect to the specified record.
Set<String>	joinFields(String fldName) Determines if there are terms of the form "F1=F2" or result in "F1=F2" via equal transitivity, where F1 is the specified field and F2 is another field (called join field).
Predicate	joinPredicate(Schema sch1, Schema sch2) Returns the sub-predicate consisting of terms that applies to the union of the two specified schemas, but not to either schema separately.
Predicate	selectPredicate(Schema sch) Returns the sub-predicate that applies to the specified schema.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

Predicate

public Predicate()

Creates an empty predicate, corresponding to "true".

Predicate

public Predicate(Term t)

Creates a predicate containing a single term.

Parameters:

t - the term

Method Detail

conjunctWith

public void conjunctWith(Term t)

Modifies the predicate to be the conjunction of itself and the specified term.

Parameters:

t - the term to conjunct with

isSatisfied

public boolean isSatisfied(Record rec)

Returns true if this predicate evaluates to true with respect to the specified record.

Parameters:

rec - the record

Returns:

true if the predicate evaluates to true

selectPredicate

public Predicate selectPredicate(Schema sch)

Returns the sub-predicate that applies to the specified schema.

Parameters:

sch - the schema

Returns:

the sub-predicate applying to the schema

joinPredicate

public Predicate joinPredicate(Schema sch1,
                               Schema sch2)

Returns the sub-predicate consisting of terms that applies to the union of the two specified schemas, but not to either schema separately.

Parameters:

sch1 - the first schema

sch2 - the second schema

Returns:

the sub-predicate whose terms apply to the union of the two schemas but not either schema separately.

constantRange

public ConstantRange constantRange(String fldName)

Determines if the specified field is constrained by a constant range in this predicate. If so, the method returns that range. If not, the method returns null.

Parameters:

fldName - the name of the field

Returns:

either the constant range or null

joinFields

public Set<String> joinFields(String fldName)

Determines if there are terms of the form "F1=F2" or result in "F1=F2" via equal transitivity, where F1 is the specified field and F2 is another field (called join field). If so, the method returns the names of all join fields. If not, the method returns null.

Parameters:

fldName - the name of the field

Returns:

the names of the join fields, or null

toString

public String toString()

Overrides:

toString in class Object