Class QueryPlan

java.lang.Object

org.projog.api.QueryPlan

public class QueryPlan
extends Object

Represents a plan for executing a Prolog query.

A single QueryPlan can be used to create multiple QueryStatement objects. If you are intending to execute the same query multiple times then, for performance reasons, it is recommended to use a QueryPlan rather than create multiple QueryStatement directly. When using a QueryPlan the Prolog syntax will only be parsed once and the plan for executing the query will be optimised for performance.

Method Summary

Modifier and Type	Method	Description
QueryStatement	createStatement()	Return a newly created QueryStatement for the query represented by this plan.
void	executeOnce()	Evaluate once the query represented by this statement.
QueryResult	executeQuery()	Return a newly created QueryResult for the query represented by this plan.
List<String>	findAllAsAtomName()
List<Double>	findAllAsDouble()
List<Long>	findAllAsLong()
List<Term>	findAllAsTerm()
String	findFirstAsAtomName()
double	findFirstAsDouble()
long	findFirstAsLong()
Optional<String>	findFirstAsOptionalAtomName()
Optional<Double>	findFirstAsOptionalDouble()
Optional<Long>	findFirstAsOptionalLong()
Optional<Term>	findFirstAsOptionalTerm()
Term	findFirstAsTerm()

Methods inherited from class Object

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

Method Details

createStatement

public QueryStatement createStatement()

Return a newly created QueryStatement for the query represented by this plan.

Before the query is executed, values can be assigned to variables in the query by using QueryStatement.setTerm(String, Term). The query can be executed by calling QueryStatement.executeQuery().

Note: If you do not intend to assign terms to variables then executeQuery() can be called instead.

See Also:

• executeQuery()
• executeOnce()

executeQuery

public QueryResult executeQuery()

Return a newly created QueryResult for the query represented by this plan.

The QueryResult.next() and QueryResult.getTerm(String) methods can be used to evaluate the query and access values unified to the variables of the query.

See Also:

• createStatement()
• executeOnce()

executeOnce

public void executeOnce()

Evaluate once the query represented by this statement.

The query will only be evaluated once, even if further solutions could of been found on backtracking.

Throws:

ProjogException - if no solution can be found

See Also:

• createStatement()
• executeQuery()

findFirstAsAtomName

public String findFirstAsAtomName()

findFirstAsDouble

public double findFirstAsDouble()

findFirstAsLong

public long findFirstAsLong()

findFirstAsTerm

public Term findFirstAsTerm()

findFirstAsOptionalAtomName

public Optional<String> findFirstAsOptionalAtomName()

findFirstAsOptionalDouble

public Optional<Double> findFirstAsOptionalDouble()

findFirstAsOptionalLong

public Optional<Long> findFirstAsOptionalLong()

findFirstAsOptionalTerm

public Optional<Term> findFirstAsOptionalTerm()

findAllAsAtomName

public List<String> findAllAsAtomName()

findAllAsDouble

public List<Double> findAllAsDouble()

findAllAsLong

public List<Long> findAllAsLong()

findAllAsTerm

public List<Term> findAllAsTerm()