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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include "fieldvalue.h"
#include <vespa/document/datatype/referencedatatype.h>
#include <vespa/document/base/documentid.h>
namespace document {
/**
* A reference field value allows search queries to access fields in other
* document instances as if they were fields natively stored within the
* searched document. This allows modelling one-to-many relations such as a
* parent document with many children containing references back to the parent.
*
* Each ReferenceFieldValue may contain a single document ID which specifies the
* instance the field should refer to. This document ID must have a type
* matching that of the reference data type of the field itself.
*
* Note that references are not polymorphic. This means that if you have a
* document type "foo" inheriting "bar", you cannot have a reference<bar> field
* containing a document ID for a "foo" document.
*/
class ReferenceFieldValue final : public FieldValue {
const ReferenceDataType* _dataType;
// TODO wrap in std::optional once available.
DocumentId _documentId;
public:
// Empty constructor required for Identifiable.
ReferenceFieldValue();
explicit ReferenceFieldValue(const ReferenceDataType& dataType);
ReferenceFieldValue(const ReferenceDataType& dataType,
const DocumentId& documentId);
~ReferenceFieldValue() override;
ReferenceFieldValue(const ReferenceFieldValue&) = default;
ReferenceFieldValue& operator=(const ReferenceFieldValue&) = default;
bool hasValidDocumentId() const noexcept {
return _documentId.hasDocType();
}
// Returned value is only well-defined if hasValidDocumentId() == true.
const DocumentId& getDocumentId() const noexcept {
return _documentId;
}
// Should only be called by deserializer code, as it will clear hasChanged.
// `id` must be a valid document ID and cannot be empty.
void setDeserializedDocumentId(const DocumentId& id);
const DataType* getDataType() const override { return _dataType; }
FieldValue& assign(const FieldValue&) override;
ReferenceFieldValue* clone() const override;
int compare(const FieldValue&) const override;
void printXml(XmlOutputStream&) const override { /* Not implemented */ }
void print(std::ostream&, bool, const std::string&) const override;
void accept(FieldValueVisitor&) override;
void accept(ConstFieldValueVisitor&) const override;
private:
// Throws vespalib::IllegalArgumentException if doc type of `id` does not
// match the name of `type`.
static void requireIdOfMatchingType(const DocumentId& id, const DocumentType& type);
};
} // document
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