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727bad78b8
Summary: Run clang-format on files under the `table` directory. Pull Request resolved: https://github.com/facebook/rocksdb/pull/10852 Reviewed By: ajkr Differential Revision: D40650732 Pulled By: anand1976 fbshipit-source-id: 2023a958e37fd6274040c5181130284600c9e0ef
403 lines
13 KiB
C++
403 lines
13 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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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 <algorithm>
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#include <array>
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#include <string>
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#include "db/dbformat.h"
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#include "db/lookup_key.h"
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#include "db/merge_context.h"
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#include "rocksdb/env.h"
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#include "rocksdb/statistics.h"
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#include "rocksdb/types.h"
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#include "util/async_file_reader.h"
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#include "util/autovector.h"
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#include "util/math.h"
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#include "util/single_thread_executor.h"
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namespace ROCKSDB_NAMESPACE {
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class GetContext;
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struct KeyContext {
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const Slice* key;
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LookupKey* lkey;
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Slice ukey_with_ts;
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Slice ukey_without_ts;
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Slice ikey;
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ColumnFamilyHandle* column_family;
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Status* s;
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MergeContext merge_context;
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SequenceNumber max_covering_tombstone_seq;
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bool key_exists;
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bool is_blob_index;
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void* cb_arg;
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PinnableSlice* value;
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std::string* timestamp;
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GetContext* get_context;
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KeyContext(ColumnFamilyHandle* col_family, const Slice& user_key,
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PinnableSlice* val, std::string* ts, Status* stat)
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: key(&user_key),
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lkey(nullptr),
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column_family(col_family),
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s(stat),
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max_covering_tombstone_seq(0),
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key_exists(false),
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is_blob_index(false),
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cb_arg(nullptr),
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value(val),
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timestamp(ts),
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get_context(nullptr) {}
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KeyContext() = default;
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};
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// The MultiGetContext class is a container for the sorted list of keys that
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// we need to lookup in a batch. Its main purpose is to make batch execution
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// easier by allowing various stages of the MultiGet lookups to operate on
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// subsets of keys, potentially non-contiguous. In order to accomplish this,
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// it defines the following classes -
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//
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// MultiGetContext::Range
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// MultiGetContext::Range::Iterator
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// MultiGetContext::Range::IteratorWrapper
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//
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// Here is an example of how this can be used -
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//
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// {
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// MultiGetContext ctx(...);
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// MultiGetContext::Range range = ctx.GetMultiGetRange();
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//
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// // Iterate to determine some subset of the keys
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// MultiGetContext::Range::Iterator start = range.begin();
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// MultiGetContext::Range::Iterator end = ...;
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//
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// // Make a new range with a subset of keys
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// MultiGetContext::Range subrange(range, start, end);
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//
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// // Define an auxillary vector, if needed, to hold additional data for
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// // each key
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// std::array<Foo, MultiGetContext::MAX_BATCH_SIZE> aux;
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//
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// // Iterate over the subrange and the auxillary vector simultaneously
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// MultiGetContext::Range::Iterator iter = subrange.begin();
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// for (; iter != subrange.end(); ++iter) {
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// KeyContext& key = *iter;
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// Foo& aux_key = aux_iter[iter.index()];
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// ...
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// }
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// }
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class MultiGetContext {
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public:
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// Limit the number of keys in a batch to this number. Benchmarks show that
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// there is negligible benefit for batches exceeding this. Keeping this < 32
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// simplifies iteration, as well as reduces the amount of stack allocations
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// that need to be performed
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static const int MAX_BATCH_SIZE = 32;
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// A bitmask of at least MAX_BATCH_SIZE - 1 bits, so that
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// Mask{1} << MAX_BATCH_SIZE is well defined
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using Mask = uint64_t;
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static_assert(MAX_BATCH_SIZE < sizeof(Mask) * 8);
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MultiGetContext(autovector<KeyContext*, MAX_BATCH_SIZE>* sorted_keys,
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size_t begin, size_t num_keys, SequenceNumber snapshot,
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const ReadOptions& read_opts, FileSystem* fs,
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Statistics* stats)
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: num_keys_(num_keys),
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value_mask_(0),
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value_size_(0),
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lookup_key_ptr_(reinterpret_cast<LookupKey*>(lookup_key_stack_buf))
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#if USE_COROUTINES
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,
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reader_(fs, stats),
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executor_(reader_)
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#endif // USE_COROUTINES
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{
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(void)fs;
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(void)stats;
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assert(num_keys <= MAX_BATCH_SIZE);
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if (num_keys > MAX_LOOKUP_KEYS_ON_STACK) {
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lookup_key_heap_buf.reset(new char[sizeof(LookupKey) * num_keys]);
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lookup_key_ptr_ = reinterpret_cast<LookupKey*>(lookup_key_heap_buf.get());
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}
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for (size_t iter = 0; iter != num_keys_; ++iter) {
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// autovector may not be contiguous storage, so make a copy
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sorted_keys_[iter] = (*sorted_keys)[begin + iter];
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sorted_keys_[iter]->lkey = new (&lookup_key_ptr_[iter])
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LookupKey(*sorted_keys_[iter]->key, snapshot, read_opts.timestamp);
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sorted_keys_[iter]->ukey_with_ts = sorted_keys_[iter]->lkey->user_key();
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sorted_keys_[iter]->ukey_without_ts = StripTimestampFromUserKey(
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sorted_keys_[iter]->lkey->user_key(),
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read_opts.timestamp == nullptr ? 0 : read_opts.timestamp->size());
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sorted_keys_[iter]->ikey = sorted_keys_[iter]->lkey->internal_key();
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sorted_keys_[iter]->timestamp = (*sorted_keys)[begin + iter]->timestamp;
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sorted_keys_[iter]->get_context =
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(*sorted_keys)[begin + iter]->get_context;
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}
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}
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~MultiGetContext() {
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for (size_t i = 0; i < num_keys_; ++i) {
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lookup_key_ptr_[i].~LookupKey();
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}
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}
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#if USE_COROUTINES
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SingleThreadExecutor& executor() { return executor_; }
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AsyncFileReader& reader() { return reader_; }
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#endif // USE_COROUTINES
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private:
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static const int MAX_LOOKUP_KEYS_ON_STACK = 16;
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alignas(
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alignof(LookupKey)) char lookup_key_stack_buf[sizeof(LookupKey) *
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MAX_LOOKUP_KEYS_ON_STACK];
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std::array<KeyContext*, MAX_BATCH_SIZE> sorted_keys_;
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size_t num_keys_;
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Mask value_mask_;
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uint64_t value_size_;
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std::unique_ptr<char[]> lookup_key_heap_buf;
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LookupKey* lookup_key_ptr_;
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#if USE_COROUTINES
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AsyncFileReader reader_;
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SingleThreadExecutor executor_;
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#endif // USE_COROUTINES
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public:
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// MultiGetContext::Range - Specifies a range of keys, by start and end index,
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// from the parent MultiGetContext. Each range contains a bit vector that
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// indicates whether the corresponding keys need to be processed or skipped.
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// A Range object can be copy constructed, and the new object inherits the
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// original Range's bit vector. This is useful for progressively skipping
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// keys as the lookup goes through various stages. For example, when looking
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// up keys in the same SST file, a Range is created excluding keys not
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// belonging to that file. A new Range is then copy constructed and individual
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// keys are skipped based on bloom filter lookup.
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class Range {
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public:
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// MultiGetContext::Range::Iterator - A forward iterator that iterates over
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// non-skippable keys in a Range, as well as keys whose final value has been
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// found. The latter is tracked by MultiGetContext::value_mask_
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class Iterator {
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public:
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// -- iterator traits
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using self_type = Iterator;
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using value_type = KeyContext;
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using reference = KeyContext&;
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using pointer = KeyContext*;
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using difference_type = int;
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using iterator_category = std::forward_iterator_tag;
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Iterator(const Range* range, size_t idx)
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: range_(range), ctx_(range->ctx_), index_(idx) {
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while (index_ < range_->end_ &&
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(Mask{1} << index_) &
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(range_->ctx_->value_mask_ | range_->skip_mask_ |
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range_->invalid_mask_))
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index_++;
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}
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Iterator(const Iterator&) = default;
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Iterator(const Iterator& other, const Range* range)
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: range_(range), ctx_(other.ctx_), index_(other.index_) {
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assert(range->ctx_ == other.ctx_);
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}
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Iterator& operator=(const Iterator&) = default;
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Iterator& operator++() {
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while (++index_ < range_->end_ &&
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(Mask{1} << index_) &
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(range_->ctx_->value_mask_ | range_->skip_mask_ |
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range_->invalid_mask_))
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;
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return *this;
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}
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bool operator==(Iterator other) const {
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assert(range_->ctx_ == other.range_->ctx_);
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return index_ == other.index_;
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}
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bool operator!=(Iterator other) const {
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assert(range_->ctx_ == other.range_->ctx_);
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return index_ != other.index_;
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}
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KeyContext& operator*() {
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assert(index_ < range_->end_ && index_ >= range_->start_);
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return *(ctx_->sorted_keys_[index_]);
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}
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KeyContext* operator->() {
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assert(index_ < range_->end_ && index_ >= range_->start_);
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return ctx_->sorted_keys_[index_];
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}
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size_t index() { return index_; }
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private:
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friend Range;
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const Range* range_;
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const MultiGetContext* ctx_;
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size_t index_;
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};
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Range(const Range& mget_range, const Iterator& first,
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const Iterator& last) {
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ctx_ = mget_range.ctx_;
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if (first == last) {
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// This means create an empty range based on mget_range. So just
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// set start_ and and_ to the same value
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start_ = mget_range.start_;
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end_ = start_;
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} else {
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start_ = first.index_;
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end_ = last.index_;
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}
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skip_mask_ = mget_range.skip_mask_;
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invalid_mask_ = mget_range.invalid_mask_;
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assert(start_ < 64);
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assert(end_ < 64);
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}
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Range() = default;
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Iterator begin() const { return Iterator(this, start_); }
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Iterator end() const { return Iterator(this, end_); }
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bool empty() const { return RemainingMask() == 0; }
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void SkipIndex(size_t index) { skip_mask_ |= Mask{1} << index; }
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void SkipKey(const Iterator& iter) { SkipIndex(iter.index_); }
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bool IsKeySkipped(const Iterator& iter) const {
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return skip_mask_ & (Mask{1} << iter.index_);
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}
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// Update the value_mask_ in MultiGetContext so its
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// immediately reflected in all the Range Iterators
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void MarkKeyDone(Iterator& iter) {
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ctx_->value_mask_ |= (Mask{1} << iter.index_);
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}
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bool CheckKeyDone(Iterator& iter) const {
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return ctx_->value_mask_ & (Mask{1} << iter.index_);
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}
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uint64_t KeysLeft() const { return BitsSetToOne(RemainingMask()); }
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void AddSkipsFrom(const Range& other) {
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assert(ctx_ == other.ctx_);
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skip_mask_ |= other.skip_mask_;
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}
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uint64_t GetValueSize() { return ctx_->value_size_; }
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void AddValueSize(uint64_t value_size) { ctx_->value_size_ += value_size; }
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MultiGetContext* context() const { return ctx_; }
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Range Suffix(const Range& other) const {
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size_t other_last = other.FindLastRemaining();
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size_t my_last = FindLastRemaining();
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if (my_last > other_last) {
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return Range(*this, Iterator(this, other_last),
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Iterator(this, my_last));
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} else {
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return Range(*this, begin(), begin());
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}
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}
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// The += operator expands the number of keys in this range. The expansion
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// is always to the right, i.e start of the additional range >= end of
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// current range. There should be no overlap. Any skipped keys in rhs are
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// marked as invalid in the invalid_mask_.
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Range& operator+=(const Range& rhs) {
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assert(rhs.start_ >= end_);
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// Check for non-overlapping ranges and adjust invalid_mask_ accordingly
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if (end_ < rhs.start_) {
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invalid_mask_ |= RangeMask(end_, rhs.start_);
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skip_mask_ |= RangeMask(end_, rhs.start_);
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}
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start_ = std::min<size_t>(start_, rhs.start_);
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end_ = std::max<size_t>(end_, rhs.end_);
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skip_mask_ |= rhs.skip_mask_ & RangeMask(rhs.start_, rhs.end_);
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invalid_mask_ |= (rhs.invalid_mask_ | rhs.skip_mask_) &
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RangeMask(rhs.start_, rhs.end_);
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assert(start_ < 64);
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assert(end_ < 64);
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return *this;
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}
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// The -= operator removes keys from this range. The removed keys should
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// come from a range completely overlapping the current range. The removed
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// keys are marked invalid in the invalid_mask_.
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Range& operator-=(const Range& rhs) {
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assert(start_ <= rhs.start_ && end_ >= rhs.end_);
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skip_mask_ |= (~rhs.skip_mask_ | rhs.invalid_mask_) &
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RangeMask(rhs.start_, rhs.end_);
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invalid_mask_ |= (~rhs.skip_mask_ | rhs.invalid_mask_) &
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RangeMask(rhs.start_, rhs.end_);
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return *this;
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}
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// Return a complement of the current range
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Range operator~() {
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Range res = *this;
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res.skip_mask_ = ~skip_mask_ & RangeMask(start_, end_);
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return res;
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}
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private:
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friend MultiGetContext;
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MultiGetContext* ctx_;
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size_t start_;
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size_t end_;
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Mask skip_mask_;
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Mask invalid_mask_;
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Range(MultiGetContext* ctx, size_t num_keys)
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: ctx_(ctx),
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start_(0),
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end_(num_keys),
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skip_mask_(0),
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invalid_mask_(0) {
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assert(num_keys < 64);
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}
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static Mask RangeMask(size_t start, size_t end) {
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return (((Mask{1} << (end - start)) - 1) << start);
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}
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Mask RemainingMask() const {
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return (((Mask{1} << end_) - 1) & ~((Mask{1} << start_) - 1) &
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~(ctx_->value_mask_ | skip_mask_));
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}
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size_t FindLastRemaining() const {
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Mask mask = RemainingMask();
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size_t index = (mask >>= start_) ? start_ : 0;
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while (mask >>= 1) {
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index++;
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}
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return index;
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}
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};
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// Return the initial range that encompasses all the keys in the batch
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Range GetMultiGetRange() { return Range(this, num_keys_); }
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};
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} // namespace ROCKSDB_NAMESPACE
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