fix(gravsearch): Prevent duplicate results

docs/src/paradox/05-internals/design/api-v2/gravsearch.md

@@ -174,16 +174,10 @@ PREFIX knora-api: <http://api.knora.org/ontology/knora-api/simple/v2#>
     }
 ```
 
-The prequery's SELECT clause is built using the member variables defined in `AbstractPrequeryGenerator`.
-State of member variables after transformation of the input query into the prequery:
-
-- `mainResourceVariable`: `QueryVariable(page)`
-- `dependentResourceVariables`: `Set(QueryVariable(book))`
-- `dependentResourceVariablesGroupConcat`: `Set(QueryVariable(book__Concat))`
-- `valueObjectVariables`: `Set(QueryVariable(book__LinkValue), QueryVariable(seqnum))`: `?book` represents the dependent resource and `?book__LinkValue` the link value connecting `?page` and `?book`.
-- `valueObjectVariablesGroupConcat`: `Set(QueryVariable(seqnum__Concat), QueryVariable(book__LinkValue__Concat))`
-
-The resulting SELECT clause of the prequery looks as follows:
+The prequery's SELECT clause is built by
+`NonTriplestoreSpecificGravsearchToPrequeryTransformer.getSelectColumns`,
+based on the variables used in the input query's `CONSTRUCT` clause.
+The resulting SELECT clause looks as follows:
 
 ```sparql
 SELECT DISTINCT
@@ -219,6 +213,11 @@ is unbound, we concatenate an empty string. This is necessary because, in Apache
 triplestores), "If `GROUP_CONCAT` has an unbound value in the list of values to concat, the overall result is 'error'"
 (see [this Jena issue](https://issues.apache.org/jira/browse/JENA-1856)).
 
+If the input query contains a `UNION`, and a variable is bound in one branch
+of the `UNION` and not in another branch, it is possible that the prequery
+will return more than one row per main resource. To deal with this situation,
+`SearchResponderV2` merges rows that contain the same main resource IRI.
+
 ### Main Query
 
 The purpose of the main query is to get all requested information about the main resource, dependent resources, and value objects.
@@ -233,8 +232,17 @@ The classes involved in generating the main query can be found in
 
 The main query is a SPARQL CONSTRUCT query. Its generation is handled by the
 method `GravsearchMainQueryGenerator.createMainQuery`.
-It takes three arguments: `mainResourceIris: Set[IriRef], dependentResourceIris:
-Set[IriRef], valueObjectIris: Set[IRI]`. From the given Iris, statements are
+It takes three arguments:
+`mainResourceIris: Set[IriRef], dependentResourceIris: Set[IriRef], valueObjectIris: Set[IRI]`.
+
+These sets are constructed based on information about variables representing
+dependent resources and value objects in the prequery, which is provided by
+`NonTriplestoreSpecificGravsearchToPrequeryTransformer`:
+
+- `dependentResourceVariablesGroupConcat`: `Set(QueryVariable(book__Concat))`
+- `valueObjectVariablesGroupConcat`: `Set(QueryVariable(seqnum__Concat), QueryVariable(book__LinkValue__Concat))`
+
+From the given Iris, statements are
 generated that ask for complete information on *exactly* these resources and
 values. For any given resource Iri, only the values present in
 `valueObjectIris` are to be queried. This is achieved by using SPARQL's

webapi/src/main/scala/org/knora/webapi/messages/v2/responder/resourcemessages/ResourceMessagesV2.scala

@@ -824,6 +824,17 @@ case class ReadResourcesSequenceV2(resources: Seq[ReadResourceV2],
         )
     }
 
+    private def getOntologiesFromResource(resource: ReadResourceV2): Set[SmartIri] = {
+        val propertyIriOntologies: Set[SmartIri] = resource.values.keySet.map(_.getOntologyFromEntity)
+
+        val valueOntologies: Set[SmartIri] = resource.values.values.flatten.collect {
+            case readLinkValueV2: ReadLinkValueV2 =>
+                readLinkValueV2.valueContent.nestedResource.map(nested => getOntologiesFromResource(nested))
+        }.flatten.flatten.toSet
+
+        propertyIriOntologies ++ valueOntologies + resource.resourceClassIri.getOntologyFromEntity
+    }
+
     // #generateJsonLD
     private def generateJsonLD(targetSchema: ApiV2Schema, settings: SettingsImpl, schemaOptions: Set[SchemaOption]): JsonLDDocument = {
         // #generateJsonLD
@@ -843,14 +854,7 @@ case class ReadResourcesSequenceV2(resources: Seq[ReadResourceV2],
         // Make JSON-LD prefixes for the project-specific ontologies used in the response.
 
         val projectSpecificOntologiesUsed: Set[SmartIri] = resources.flatMap {
-            resource =>
-                val resourceOntology = resource.resourceClassIri.getOntologyFromEntity
-
-                val propertyOntologies = resource.values.keySet.map {
-                    property => property.getOntologyFromEntity
-                }
-
-                propertyOntologies + resourceOntology
+            resource => getOntologiesFromResource(resource)
         }.toSet.filter(!_.isKnoraBuiltInDefinitionIri)
 
         // Make the knora-api prefix for the target schema.

webapi/src/main/scala/org/knora/webapi/responders/v1/ValuesResponderV1.scala

@@ -744,7 +744,7 @@ class ValuesResponderV1(responderData: ResponderData) extends Responder(responde
             // If we're updating a link, findResourceWithValueResult will contain the IRI of the property that points to the
             // knora-base:LinkValue, but we'll need the IRI of the corresponding link property.
             val propertyIri = changeValueRequest.value match {
-                case linkUpdateV1: LinkUpdateV1 => stringFormatter.linkValuePropertyIri2LinkPropertyIri(findResourceWithValueResult.propertyIri)
+                case linkUpdateV1: LinkUpdateV1 => stringFormatter.linkValuePropertyIriToLinkPropertyIri(findResourceWithValueResult.propertyIri)
                 case _ => findResourceWithValueResult.propertyIri
             }
 
@@ -1075,7 +1075,7 @@ class ValuesResponderV1(responderData: ResponderData) extends Responder(responde
                         case (p, o) => p == OntologyConstants.KnoraBase.HasPermissions
                     }.map(_._2).getOrElse(throw InconsistentTriplestoreDataException(s"Value ${deleteValueRequest.valueIri} has no permissions"))
 
-                    val linkPropertyIri = stringFormatter.linkValuePropertyIri2LinkPropertyIri(findResourceWithValueResult.propertyIri)
+                    val linkPropertyIri = stringFormatter.linkValuePropertyIriToLinkPropertyIri(findResourceWithValueResult.propertyIri)
 
                     for {
                         // Get project info

webapi/src/main/scala/org/knora/webapi/responders/v2/ResourcesResponderV2.scala

@@ -1210,6 +1210,7 @@ class ResourcesResponderV2(responderData: ResponderData) extends ResponderWithSt
             apiResponse: ReadResourcesSequenceV2 <- ConstructResponseUtilV2.createApiResponse(
                 mainResourcesAndValueRdfData = mainResourcesAndValueRdfData,
                 orderByResourceIri = resourceIrisDistinct,
+                pageSizeBeforeFiltering = resourceIris.size, // doesn't matter because we're not doing paging
                 mappings = mappingsAsMap,
                 queryStandoff = queryStandoff,
                 versionDate = versionDate,
@@ -1264,6 +1265,7 @@ class ResourcesResponderV2(responderData: ResponderData) extends ResponderWithSt
             apiResponse: ReadResourcesSequenceV2 <- ConstructResponseUtilV2.createApiResponse(
                 mainResourcesAndValueRdfData = mainResourcesAndValueRdfData,
                 orderByResourceIri = resourceIrisDistinct,
+                pageSizeBeforeFiltering = resourceIris.size, // doesn't matter because we're not doing paging
                 mappings = Map.empty[IRI, MappingAndXSLTransformation],
                 queryStandoff = false,
                 versionDate = None,