Package cz.cvut.kbss.jopa.query.sparql.loader

Class AttributeEnumeratingSparqlAssemblyModifier

java.lang.Object

cz.cvut.kbss.jopa.query.sparql.loader.AttributeEnumeratingSparqlAssemblyModifier

All Implemented Interfaces:

SparqlAssemblyModifier

public class AttributeEnumeratingSparqlAssemblyModifier
extends Object
implements SparqlAssemblyModifier

Optimizes entity loading by modifying the query to fetch all named attributes.

This optimizer is applicable for SELECT queries that select instances of an entity class. Instead of loading the instances one by one after the query is evaluated, this optimizer modifies the query to fetch all available entity attributes by injecting optional triple patterns for each of the entity attributes and projecting the values from the query. If the result type has subclasses, all attributes of the subclasses are enumerated in the query so that the instance loading can then determine the result type and load the appropriate instance with all the relevant attribute data.

The injected patterns look like this:

 OPTIONAL { ?subject <property> ?value }
 

If a descriptor with at most one context (for each attribute) is provided, the injected patterns look like this:

 OPTIONAL { GRAPH ?g { ?subject <property> ?value } }
 

Where ?g is determined from the descriptor.

When not to use this modifier:

• When the result type has Properties field

Constructor Summary

Constructors

Constructor	Description
AttributeEnumeratingSparqlAssemblyModifier(IdentifiableEntityType<?> resultType, Descriptor descriptor)

Method Summary

Modifier and Type	Method	Description
void	modify(TokenStreamSparqlQueryHolder queryHolder, org.antlr.v4.runtime.TokenStreamRewriter tokenRewriter, QueryAttributes queryAttributes)	Modifies the query.

Methods inherited from class java.lang.Object

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

Constructor Details

AttributeEnumeratingSparqlAssemblyModifier

public AttributeEnumeratingSparqlAssemblyModifier(IdentifiableEntityType<?> resultType,
 Descriptor descriptor)

Method Details

modify

public void modify(TokenStreamSparqlQueryHolder queryHolder,
 org.antlr.v4.runtime.TokenStreamRewriter tokenRewriter,
 QueryAttributes queryAttributes)

Description copied from interface: SparqlAssemblyModifier

Modifies the query.

Specified by:

modify in interface SparqlAssemblyModifier

Parameters:

queryHolder - Query holder

tokenRewriter - Token stream rewriter used to modify the query

queryAttributes - Query attributes