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d34712e0ac
Summary: Continuing from the previous MultiCfIterator Implementations - (https://github.com/facebook/rocksdb/issues/12422, https://github.com/facebook/rocksdb/issues/12480 #12465), this PR completes the `AttributeGroupIterator` by implementing `AttributeGroupIteratorImpl::AddToAttributeGroups()`. While implementing the `AttributeGroupIterator`, we had to make some changes in `MultiCfIteratorImpl` and found an opportunity to improve `Coalesce()` in `CoalescingIterator`. Lifting `UNDER CONSTRUCTION - DO NOT USE` comment by replacing it with `EXPERIMENTAL` Here are some implementation details: - `IteratorAttributeGroups` is introduced to avoid having to copy all `WideColumn` objects during iteration. - `PopulateIterator()` no longer advances non-top iterators that have the same key as the top iterator in the heap. - `AdvanceIterator()` needs to advance the non-top iterators when they have the same key as the top iterator in the heap. - Instead of populating one by one, `PopulateIterator()` now collects all items with the same key and calls `populate_func(items)` at once. - This allowed optimization in `Coalesce()` such that we no longer do K-1 rounds of 2-way merge, but do one K-way merge instead. Pull Request resolved: https://github.com/facebook/rocksdb/pull/12534 Test Plan: Uncommented the assertions in `verifyAttributeGroupIterator()` ``` ./multi_cf_iterator_test ``` Reviewed By: ltamasi Differential Revision: D56089019 Pulled By: jaykorean fbshipit-source-id: 6b0b4247e221f69b40b147d41492008cc9b15054
80 lines
2.4 KiB
C++
80 lines
2.4 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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#pragma once
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#include "db/multi_cf_iterator_impl.h"
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namespace ROCKSDB_NAMESPACE {
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// EXPERIMENTAL
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class CoalescingIterator : public Iterator {
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public:
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CoalescingIterator(const Comparator* comparator,
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const std::vector<ColumnFamilyHandle*>& column_families,
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const std::vector<Iterator*>& child_iterators)
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: impl_(
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comparator, column_families, child_iterators, [this]() { Reset(); },
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[this](const autovector<MultiCfIteratorInfo>& items) {
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Coalesce(items);
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}) {}
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~CoalescingIterator() override {}
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// No copy allowed
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CoalescingIterator(const CoalescingIterator&) = delete;
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CoalescingIterator& operator=(const CoalescingIterator&) = delete;
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bool Valid() const override { return impl_.Valid(); }
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void SeekToFirst() override { impl_.SeekToFirst(); }
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void SeekToLast() override { impl_.SeekToLast(); }
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void Seek(const Slice& target) override { impl_.Seek(target); }
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void SeekForPrev(const Slice& target) override { impl_.SeekForPrev(target); }
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void Next() override { impl_.Next(); }
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void Prev() override { impl_.Prev(); }
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Slice key() const override { return impl_.key(); }
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Status status() const override { return impl_.status(); }
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Slice value() const override {
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assert(Valid());
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return value_;
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}
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const WideColumns& columns() const override {
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assert(Valid());
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return wide_columns_;
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}
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void Reset() {
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value_.clear();
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wide_columns_.clear();
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}
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private:
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MultiCfIteratorImpl impl_;
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Slice value_;
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WideColumns wide_columns_;
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struct WideColumnWithOrder {
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const WideColumn* column;
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int order;
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};
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class WideColumnWithOrderComparator {
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public:
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explicit WideColumnWithOrderComparator() {}
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bool operator()(const WideColumnWithOrder& a,
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const WideColumnWithOrder& b) const {
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int c = a.column->name().compare(b.column->name());
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return c == 0 ? a.order - b.order > 0 : c > 0;
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}
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};
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using MinHeap =
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BinaryHeap<WideColumnWithOrder, WideColumnWithOrderComparator>;
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void Coalesce(const autovector<MultiCfIteratorInfo>& items);
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};
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} // namespace ROCKSDB_NAMESPACE
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