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db1dea22b1
Summary: This PR continues https://github.com/facebook/rocksdb/issues/12153 by implementing the missing `Iterator` APIs - `Seek()`, `SeekForPrev()`, `SeekToLast()`, and `Prev`. A MaxHeap Implementation has been added to handle the reverse direction. The current implementation does not include upper/lower bounds yet. These will be added in subsequent PRs. The API is still marked as under construction and will be lifted after being added to the stress test. Please note that changing the iterator direction in the middle of iteration is expensive, as it requires seeking the element in each iterator again in the opposite direction and rebuilding the heap along the way. The first `Next()` after `SeekForPrev()` requires changing the direction under the current implementation. We may optimize this in later PRs. Pull Request resolved: https://github.com/facebook/rocksdb/pull/12422 Test Plan: The `multi_cf_iterator_test` has been extended to cover the API implementations. Reviewed By: pdillinger Differential Revision: D54820754 Pulled By: jaykorean fbshipit-source-id: 9eb741508df0f7bad598fb8e6bd5cdffc39e81d1
104 lines
3.1 KiB
C++
104 lines
3.1 KiB
C++
// Copyright (c) Meta Platforms, Inc. and affiliates.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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#include "db/multi_cf_iterator.h"
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#include <cassert>
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namespace ROCKSDB_NAMESPACE {
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void MultiCfIterator::SeekCommon(
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const std::function<void(Iterator*)>& child_seek_func,
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Direction direction) {
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direction_ = direction;
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Reset();
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int i = 0;
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for (auto& cfh_iter_pair : cfh_iter_pairs_) {
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auto& cfh = cfh_iter_pair.first;
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auto& iter = cfh_iter_pair.second;
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child_seek_func(iter.get());
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if (iter->Valid()) {
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assert(iter->status().ok());
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if (direction_ == kReverse) {
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auto& max_heap = std::get<MultiCfMaxHeap>(heap_);
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max_heap.push(MultiCfIteratorInfo{iter.get(), cfh, i});
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} else {
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auto& min_heap = std::get<MultiCfMinHeap>(heap_);
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min_heap.push(MultiCfIteratorInfo{iter.get(), cfh, i});
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}
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} else {
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considerStatus(iter->status());
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}
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++i;
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}
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}
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template <typename BinaryHeap>
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void MultiCfIterator::AdvanceIterator(
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BinaryHeap& heap, const std::function<void(Iterator*)>& advance_func) {
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// 1. Keep the top iterator (by popping it from the heap)
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// 2. Make sure all others have iterated past the top iterator key slice
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// 3. Advance the top iterator, and add it back to the heap if valid
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auto top = heap.top();
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heap.pop();
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if (!heap.empty()) {
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auto* current = heap.top().iterator;
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while (current->Valid() &&
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comparator_->Compare(top.iterator->key(), current->key()) == 0) {
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assert(current->status().ok());
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advance_func(current);
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if (current->Valid()) {
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heap.replace_top(heap.top());
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} else {
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considerStatus(current->status());
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heap.pop();
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}
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if (!heap.empty()) {
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current = heap.top().iterator;
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}
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}
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}
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advance_func(top.iterator);
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if (top.iterator->Valid()) {
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assert(top.iterator->status().ok());
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heap.push(top);
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} else {
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considerStatus(top.iterator->status());
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}
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}
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void MultiCfIterator::SeekToFirst() {
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SeekCommon([](Iterator* iter) { iter->SeekToFirst(); }, kForward);
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}
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void MultiCfIterator::Seek(const Slice& target) {
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SeekCommon([&target](Iterator* iter) { iter->Seek(target); }, kForward);
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}
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void MultiCfIterator::SeekToLast() {
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SeekCommon([](Iterator* iter) { iter->SeekToLast(); }, kReverse);
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}
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void MultiCfIterator::SeekForPrev(const Slice& target) {
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SeekCommon([&target](Iterator* iter) { iter->SeekForPrev(target); },
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kReverse);
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}
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void MultiCfIterator::Next() {
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assert(Valid());
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if (direction_ != kForward) {
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SwitchToDirection(kForward);
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}
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auto& min_heap = std::get<MultiCfMinHeap>(heap_);
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AdvanceIterator(min_heap, [](Iterator* iter) { iter->Next(); });
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}
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void MultiCfIterator::Prev() {
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assert(Valid());
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if (direction_ != kReverse) {
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SwitchToDirection(kReverse);
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}
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auto& max_heap = std::get<MultiCfMaxHeap>(heap_);
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AdvanceIterator(max_heap, [](Iterator* iter) { iter->Prev(); });
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}
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} // namespace ROCKSDB_NAMESPACE
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