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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include <vespa/vespalib/btree/btree_key_data.h>
#include <vespa/searchlib/common/bitvector.h>
#include <vespa/vespalib/util/arrayref.h>
namespace search::attribute {
/*
* Class providing a synthetic posting list by merging multiple posting lists
* into an array or bitvector.
*/
template <typename DataT>
class PostingListMerger
{
using Posting = vespalib::btree::BTreeKeyData<uint32_t, DataT>;
using PostingVector = std::vector<Posting>;
using StartVector = std::vector<size_t>;
PostingVector _array;
StartVector _startPos;
std::shared_ptr<BitVector> _bitVector;
uint32_t _docIdLimit;
bool _arrayValid;
PostingVector &merge(PostingVector &v, PostingVector &temp, const StartVector &startPos) __attribute__((noinline));
public:
PostingListMerger(uint32_t docIdLimit) noexcept;
~PostingListMerger();
void reserveArray(uint32_t postingsCount, size_t postingsSize);
void allocBitVector();
void merge();
bool hasArray() const noexcept { return _arrayValid; }
bool hasBitVector() const noexcept { return static_cast<bool>(_bitVector); }
bool emptyArray() const noexcept { return _array.empty(); }
vespalib::ConstArrayRef<Posting> getArray() const noexcept { return _array; }
const BitVector *getBitVector() const noexcept { return _bitVector.get(); }
const std::shared_ptr<BitVector> &getBitVectorSP() const noexcept { return _bitVector; }
uint32_t getDocIdLimit() const noexcept { return _docIdLimit; }
template <typename PostingListType>
void addToArray(const PostingListType & postingList)
{
PostingVector &array = _array;
postingList.foreach([&array](uint32_t key, const DataT &data)
{ array.emplace_back(key, data); });
if (_startPos.back() < array.size()) {
_startPos.push_back(array.size());
}
}
template <typename PostingListType>
void addToBitVector(const PostingListType & postingList)
{
BitVector &bv = *_bitVector;
uint32_t limit = _docIdLimit;
postingList.foreach_key([&bv, limit](uint32_t key)
{ if (__builtin_expect(key < limit, true)) { bv.setBit(key); } });
}
bool merge_done() const noexcept { return hasArray() || hasBitVector(); }
// Until diversity handling has been rewritten
PostingVector &getWritableArray() noexcept { return _array; }
StartVector &getWritableStartPos() noexcept { return _startPos; }
};
}
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