Package graphql.schema.diffing

Class PossibleMappingsCalculator

java.lang.Object

graphql.schema.diffing.PossibleMappingsCalculator

public class PossibleMappingsCalculator
extends Object

We don't want to allow arbitrary schema changes. For example changing an Object type into a Scalar is not something we want to consider.

We do this to make SchemaDiffings better understandable, but also to improve the overall runtime of the algorithm. By restricting the possible mappings the Schema diffing algo is actually able to finish in a reasonable time for real life inputs.

We restrict the algo by calculating which mappings are possible for given vertex. This is later used in DiffImpl.calcLowerBoundMappingCost(graphql.schema.diffing.Vertex, graphql.schema.diffing.Vertex, graphql.schema.diffing.Mapping, java.util.Map<graphql.schema.diffing.Vertex, java.lang.Double>, java.util.Map<graphql.schema.diffing.Vertex, graphql.schema.diffing.Vertex>). While doing this we need to also ensure that there are the same amount of vertices in the same "context": for example if the source graph has 3 Objects, the target graph needs to have 3 Objects. We achieve this by adding "isolated vertices" as needed.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
class	PossibleMappingsCalculator.PossibleMappings
static class	PossibleMappingsCalculator.VertexContextSegment

Constructor Summary

Constructors

Constructor	Description
PossibleMappingsCalculator(SchemaGraph sourceGraph, SchemaGraph targetGraph, graphql.schema.diffing.SchemaDiffingRunningCheck runningCheck)

Method Summary

Modifier and Type	Method	Description
void	calcPossibleMappings(List<PossibleMappingsCalculator.VertexContextSegment> contexts, String typeNameForDebug)
PossibleMappingsCalculator.PossibleMappings	calculate()
Map<Vertex,Vertex>	getFixedParentRestrictions()
Map<Vertex,Vertex>	getFixedParentRestrictionsInverse(Map<Vertex,Vertex> fixedOneToOneMappingsInverted)
Map<Vertex,Vertex>	getNonFixedParentRestrictions(SchemaGraph sourceGraph, SchemaGraph targetGraph, Mapping mapping)	This computes the initial set of parent restrictions based on the given non-fixed mapping.
static boolean	hasChildrenRestrictions(Vertex vertex)
static boolean	hasParentRestrictions(Vertex vertex)

Methods inherited from class java.lang.Object

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

Constructor Details

PossibleMappingsCalculator

public PossibleMappingsCalculator(SchemaGraph sourceGraph,
 SchemaGraph targetGraph,
 graphql.schema.diffing.SchemaDiffingRunningCheck runningCheck)

Method Details

calculate

public PossibleMappingsCalculator.PossibleMappings calculate()

calcPossibleMappings

public void calcPossibleMappings(List<PossibleMappingsCalculator.VertexContextSegment> contexts,
 String typeNameForDebug)

getFixedParentRestrictions

public Map<Vertex,Vertex> getFixedParentRestrictions()

getFixedParentRestrictionsInverse

public Map<Vertex,Vertex> getFixedParentRestrictionsInverse(Map<Vertex,Vertex> fixedOneToOneMappingsInverted)

getNonFixedParentRestrictions

public Map<Vertex,Vertex> getNonFixedParentRestrictions(SchemaGraph sourceGraph,
 SchemaGraph targetGraph,
 Mapping mapping)

This computes the initial set of parent restrictions based on the given non-fixed mapping.

i.e. this introduces restrictions as the Mapping is being built, as decisions can have knock on effects on other vertices' possible mappings.

See Mapping for definition of fixed vs non-fixed.

If a Vertex is present in the output Map then the value is the parent the vertex MUST map to.

e.g. for an output {collar: Dog} then the collar vertex must be a child of Dog in the mapping.

Parameters:

sourceGraph - the source graph

targetGraph - the target graph

mapping - the mapping to get non-fixed parent restrictions for

Returns:

Map where key is any vertex, and the value is the parent that vertex must map to

hasParentRestrictions

public static boolean hasParentRestrictions(Vertex vertex)

hasChildrenRestrictions

public static boolean hasChildrenRestrictions(Vertex vertex)