Add imported attribute vector (#1847)

1 files changed, 73 insertions, 0 deletions

diff --git a/searchlib/src/vespa/searchlib/attribute/imported_attribute_vector.h b/searchlib/src/vespa/searchlib/attribute/imported_attribute_vector.h
new file mode 100644
index 00000000000..97f1606f125
--- /dev/null
+++ b/searchlib/src/vespa/searchlib/attribute/imported_attribute_vector.h
@@ -0,0 +1,73 @@
+// Copyright 2017 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#pragma once
+
+#include "reference_attribute.h"
+#include <vespa/searchcommon/attribute/iattributevector.h>
+#include <vespa/vespalib/stllike/string.h>
+#include <memory>
+
+namespace search {
+namespace attribute {
+
+/**
+ * Attribute vector which does not store values of its own, but rather serves as a
+ * convenient indirection wrapper towards a target vector, usually in another
+ * document type altogether. Imported attributes are meant to be used in conjunction
+ * with a reference attribute, which specifies a dynamic mapping from a local LID to
+ * a target LID (via an intermediate GID).
+ *
+ * Any accessor on the imported attribute for a local LID yields the same result as
+ * if the same accessor were invoked with the target LID on the target attribute vector.
+ */
+class ImportedAttributeVector : public IAttributeVector {
+public:
+    ImportedAttributeVector(vespalib::stringref name,
+                            std::shared_ptr<ReferenceAttribute> reference_attribute,
+                            std::shared_ptr<AttributeVector> target_attribute);
+    ~ImportedAttributeVector();
+
+    const vespalib::string & getName() const override;
+    uint32_t getNumDocs() const override;
+    uint32_t getValueCount(uint32_t doc) const override;
+    uint32_t getMaxValueCount() const override;
+    largeint_t getInt(DocId doc) const override;
+    double getFloat(DocId doc) const override;
+    const char * getString(DocId doc, char * buffer, size_t sz) const override;
+    EnumHandle getEnum(DocId doc) const override;
+    uint32_t get(DocId docId, largeint_t * buffer, uint32_t sz) const override;
+    uint32_t get(DocId docId, double * buffer, uint32_t sz) const override;
+    uint32_t get(DocId docId, const char ** buffer, uint32_t sz) const override;
+    uint32_t get(DocId docId, EnumHandle * buffer, uint32_t sz) const override;
+    uint32_t get(DocId docId, WeightedInt * buffer, uint32_t sz) const override;
+    uint32_t get(DocId docId, WeightedFloat * buffer, uint32_t sz) const override;
+    uint32_t get(DocId docId, WeightedString * buffer, uint32_t sz) const override;
+    uint32_t get(DocId docId, WeightedConstChar * buffer, uint32_t sz) const override;
+    uint32_t get(DocId docId, WeightedEnum * buffer, uint32_t sz) const override;
+    bool findEnum(const char * value, EnumHandle & e) const override;
+    BasicType::Type getBasicType() const override;
+    size_t getFixedWidth() const override;
+    CollectionType::Type getCollectionType() const override;
+    bool hasEnum() const override;
+
+    const std::shared_ptr<ReferenceAttribute>& getReferenceAttribute() const noexcept {
+        return _reference_attribute;
+    }
+    const std::shared_ptr<AttributeVector>& getTargetAttribute() const noexcept {
+        return _target_attribute;
+    }
+
+private:
+    long onSerializeForAscendingSort(DocId doc, void * serTo, long available,
+                                     const common::BlobConverter * bc) const override;
+    long onSerializeForDescendingSort(DocId doc, void * serTo, long available,
+                                      const common::BlobConverter * bc) const override;
+
+
+    vespalib::string                    _name;
+    std::shared_ptr<ReferenceAttribute> _reference_attribute;
+    std::shared_ptr<AttributeVector>   _target_attribute;
+};
+
+} // attribute
+} // search
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