45b9bb0331
Summary: Currently metadata_block_size controls only index partition size. With this patch a partition is cut after any of index or filter partitions reaches metadata_block_size. Closes https://github.com/facebook/rocksdb/pull/2452 Differential Revision: D5275651 Pulled By: maysamyabandeh fbshipit-source-id: 5057e4424b4c8902043782e6bf8c38f0c4f25160
345 lines
14 KiB
C++
345 lines
14 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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// This source code is also licensed under the GPLv2 license found in the
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// COPYING file in the root directory of this source tree.
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//
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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#pragma once
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#include <assert.h>
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#include <inttypes.h>
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#include <list>
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#include <string>
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#include <unordered_map>
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#include "rocksdb/comparator.h"
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#include "table/block_based_table_factory.h"
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#include "table/block_builder.h"
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#include "table/format.h"
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namespace rocksdb {
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// The interface for building index.
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// Instruction for adding a new concrete IndexBuilder:
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// 1. Create a subclass instantiated from IndexBuilder.
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// 2. Add a new entry associated with that subclass in TableOptions::IndexType.
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// 3. Add a create function for the new subclass in CreateIndexBuilder.
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// Note: we can devise more advanced design to simplify the process for adding
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// new subclass, which will, on the other hand, increase the code complexity and
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// catch unwanted attention from readers. Given that we won't add/change
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// indexes frequently, it makes sense to just embrace a more straightforward
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// design that just works.
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class IndexBuilder {
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public:
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static IndexBuilder* CreateIndexBuilder(
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BlockBasedTableOptions::IndexType index_type,
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const rocksdb::InternalKeyComparator* comparator,
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const InternalKeySliceTransform* int_key_slice_transform,
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const BlockBasedTableOptions& table_opt);
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// Index builder will construct a set of blocks which contain:
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// 1. One primary index block.
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// 2. (Optional) a set of metablocks that contains the metadata of the
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// primary index.
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struct IndexBlocks {
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Slice index_block_contents;
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std::unordered_map<std::string, Slice> meta_blocks;
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};
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explicit IndexBuilder(const InternalKeyComparator* comparator)
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: comparator_(comparator) {}
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virtual ~IndexBuilder() {}
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// Add a new index entry to index block.
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// To allow further optimization, we provide `last_key_in_current_block` and
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// `first_key_in_next_block`, based on which the specific implementation can
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// determine the best index key to be used for the index block.
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// @last_key_in_current_block: this parameter maybe overridden with the value
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// "substitute key".
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// @first_key_in_next_block: it will be nullptr if the entry being added is
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// the last one in the table
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//
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// REQUIRES: Finish() has not yet been called.
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virtual void AddIndexEntry(std::string* last_key_in_current_block,
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const Slice* first_key_in_next_block,
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const BlockHandle& block_handle) = 0;
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// This method will be called whenever a key is added. The subclasses may
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// override OnKeyAdded() if they need to collect additional information.
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virtual void OnKeyAdded(const Slice& key) {}
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// Inform the index builder that all entries has been written. Block builder
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// may therefore perform any operation required for block finalization.
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//
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// REQUIRES: Finish() has not yet been called.
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inline Status Finish(IndexBlocks* index_blocks) {
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// Throw away the changes to last_partition_block_handle. It has no effect
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// on the first call to Finish anyway.
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BlockHandle last_partition_block_handle;
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return Finish(index_blocks, last_partition_block_handle);
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}
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// This override of Finish can be utilized to build the 2nd level index in
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// PartitionIndexBuilder.
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//
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// index_blocks will be filled with the resulting index data. If the return
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// value is Status::InComplete() then it means that the index is partitioned
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// and the callee should keep calling Finish until Status::OK() is returned.
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// In that case, last_partition_block_handle is pointer to the block written
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// with the result of the last call to Finish. This can be utilized to build
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// the second level index pointing to each block of partitioned indexes. The
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// last call to Finish() that returns Status::OK() populates index_blocks with
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// the 2nd level index content.
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virtual Status Finish(IndexBlocks* index_blocks,
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const BlockHandle& last_partition_block_handle) = 0;
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// Get the estimated size for index block.
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virtual size_t EstimatedSize() const = 0;
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protected:
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const InternalKeyComparator* comparator_;
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};
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// This index builder builds space-efficient index block.
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//
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// Optimizations:
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// 1. Made block's `block_restart_interval` to be 1, which will avoid linear
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// search when doing index lookup (can be disabled by setting
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// index_block_restart_interval).
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// 2. Shorten the key length for index block. Other than honestly using the
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// last key in the data block as the index key, we instead find a shortest
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// substitute key that serves the same function.
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class ShortenedIndexBuilder : public IndexBuilder {
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public:
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explicit ShortenedIndexBuilder(const InternalKeyComparator* comparator,
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int index_block_restart_interval)
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: IndexBuilder(comparator),
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index_block_builder_(index_block_restart_interval) {}
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virtual void AddIndexEntry(std::string* last_key_in_current_block,
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const Slice* first_key_in_next_block,
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const BlockHandle& block_handle) override {
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if (first_key_in_next_block != nullptr) {
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comparator_->FindShortestSeparator(last_key_in_current_block,
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*first_key_in_next_block);
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} else {
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comparator_->FindShortSuccessor(last_key_in_current_block);
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}
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std::string handle_encoding;
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block_handle.EncodeTo(&handle_encoding);
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index_block_builder_.Add(*last_key_in_current_block, handle_encoding);
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}
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using IndexBuilder::Finish;
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virtual Status Finish(
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IndexBlocks* index_blocks,
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const BlockHandle& last_partition_block_handle) override {
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index_blocks->index_block_contents = index_block_builder_.Finish();
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return Status::OK();
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}
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virtual size_t EstimatedSize() const override {
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return index_block_builder_.CurrentSizeEstimate();
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}
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friend class PartitionedIndexBuilder;
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private:
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BlockBuilder index_block_builder_;
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};
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// HashIndexBuilder contains a binary-searchable primary index and the
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// metadata for secondary hash index construction.
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// The metadata for hash index consists two parts:
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// - a metablock that compactly contains a sequence of prefixes. All prefixes
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// are stored consectively without any metadata (like, prefix sizes) being
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// stored, which is kept in the other metablock.
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// - a metablock contains the metadata of the prefixes, including prefix size,
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// restart index and number of block it spans. The format looks like:
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//
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// +-----------------+---------------------------+---------------------+
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// <=prefix 1
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// | length: 4 bytes | restart interval: 4 bytes | num-blocks: 4 bytes |
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// +-----------------+---------------------------+---------------------+
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// <=prefix 2
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// | length: 4 bytes | restart interval: 4 bytes | num-blocks: 4 bytes |
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// +-----------------+---------------------------+---------------------+
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// | |
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// | .... |
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// | |
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// +-----------------+---------------------------+---------------------+
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// <=prefix n
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// | length: 4 bytes | restart interval: 4 bytes | num-blocks: 4 bytes |
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// +-----------------+---------------------------+---------------------+
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//
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// The reason of separating these two metablocks is to enable the efficiently
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// reuse the first metablock during hash index construction without unnecessary
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// data copy or small heap allocations for prefixes.
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class HashIndexBuilder : public IndexBuilder {
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public:
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explicit HashIndexBuilder(const InternalKeyComparator* comparator,
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const SliceTransform* hash_key_extractor,
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int index_block_restart_interval)
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: IndexBuilder(comparator),
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primary_index_builder_(comparator, index_block_restart_interval),
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hash_key_extractor_(hash_key_extractor) {}
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virtual void AddIndexEntry(std::string* last_key_in_current_block,
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const Slice* first_key_in_next_block,
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const BlockHandle& block_handle) override {
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++current_restart_index_;
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primary_index_builder_.AddIndexEntry(last_key_in_current_block,
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first_key_in_next_block, block_handle);
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}
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virtual void OnKeyAdded(const Slice& key) override {
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auto key_prefix = hash_key_extractor_->Transform(key);
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bool is_first_entry = pending_block_num_ == 0;
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// Keys may share the prefix
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if (is_first_entry || pending_entry_prefix_ != key_prefix) {
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if (!is_first_entry) {
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FlushPendingPrefix();
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}
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// need a hard copy otherwise the underlying data changes all the time.
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// TODO(kailiu) ToString() is expensive. We may speed up can avoid data
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// copy.
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pending_entry_prefix_ = key_prefix.ToString();
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pending_block_num_ = 1;
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pending_entry_index_ = static_cast<uint32_t>(current_restart_index_);
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} else {
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// entry number increments when keys share the prefix reside in
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// different data blocks.
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auto last_restart_index = pending_entry_index_ + pending_block_num_ - 1;
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assert(last_restart_index <= current_restart_index_);
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if (last_restart_index != current_restart_index_) {
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++pending_block_num_;
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}
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}
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}
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virtual Status Finish(
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IndexBlocks* index_blocks,
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const BlockHandle& last_partition_block_handle) override {
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FlushPendingPrefix();
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primary_index_builder_.Finish(index_blocks, last_partition_block_handle);
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index_blocks->meta_blocks.insert(
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{kHashIndexPrefixesBlock.c_str(), prefix_block_});
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index_blocks->meta_blocks.insert(
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{kHashIndexPrefixesMetadataBlock.c_str(), prefix_meta_block_});
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return Status::OK();
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}
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virtual size_t EstimatedSize() const override {
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return primary_index_builder_.EstimatedSize() + prefix_block_.size() +
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prefix_meta_block_.size();
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}
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private:
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void FlushPendingPrefix() {
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prefix_block_.append(pending_entry_prefix_.data(),
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pending_entry_prefix_.size());
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PutVarint32Varint32Varint32(
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&prefix_meta_block_,
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static_cast<uint32_t>(pending_entry_prefix_.size()),
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pending_entry_index_, pending_block_num_);
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}
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ShortenedIndexBuilder primary_index_builder_;
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const SliceTransform* hash_key_extractor_;
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// stores a sequence of prefixes
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std::string prefix_block_;
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// stores the metadata of prefixes
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std::string prefix_meta_block_;
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// The following 3 variables keeps unflushed prefix and its metadata.
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// The details of block_num and entry_index can be found in
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// "block_hash_index.{h,cc}"
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uint32_t pending_block_num_ = 0;
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uint32_t pending_entry_index_ = 0;
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std::string pending_entry_prefix_;
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uint64_t current_restart_index_ = 0;
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};
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/**
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* IndexBuilder for two-level indexing. Internally it creates a new index for
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* each partition and Finish then in order when Finish is called on it
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* continiously until Status::OK() is returned.
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*
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* The format on the disk would be I I I I I I IP where I is block containing a
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* partition of indexes built using ShortenedIndexBuilder and IP is a block
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* containing a secondary index on the partitions, built using
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* ShortenedIndexBuilder.
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*/
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class PartitionedIndexBuilder : public IndexBuilder {
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public:
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static PartitionedIndexBuilder* CreateIndexBuilder(
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const rocksdb::InternalKeyComparator* comparator,
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const BlockBasedTableOptions& table_opt);
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explicit PartitionedIndexBuilder(const InternalKeyComparator* comparator,
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const BlockBasedTableOptions& table_opt);
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virtual ~PartitionedIndexBuilder();
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virtual void AddIndexEntry(std::string* last_key_in_current_block,
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const Slice* first_key_in_next_block,
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const BlockHandle& block_handle) override;
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virtual Status Finish(
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IndexBlocks* index_blocks,
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const BlockHandle& last_partition_block_handle) override;
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virtual size_t EstimatedSize() const override;
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size_t EstimateTopLevelIndexSize(uint64_t) const;
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size_t NumPartitions() const;
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inline bool ShouldCutFilterBlock() {
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// Current policy is to align the partitions of index and filters
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if (cut_filter_block) {
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cut_filter_block = false;
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return true;
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}
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return false;
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}
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std::string& GetPartitionKey() { return sub_index_last_key_; }
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// Called when an external entity (such as filter partition builder) request
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// cutting the next partition
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void RequestPartitionCut();
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private:
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void MakeNewSubIndexBuilder();
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struct Entry {
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std::string key;
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std::unique_ptr<ShortenedIndexBuilder> value;
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};
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std::list<Entry> entries_; // list of partitioned indexes and their keys
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BlockBuilder index_block_builder_; // top-level index builder
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// the active partition index builder
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ShortenedIndexBuilder* sub_index_builder_;
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// the last key in the active partition index builder
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std::string sub_index_last_key_;
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std::unique_ptr<FlushBlockPolicy> flush_policy_;
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// true if Finish is called once but not complete yet.
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bool finishing_indexes = false;
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const BlockBasedTableOptions& table_opt_;
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// true if an external entity (such as filter partition builder) request
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// cutting the next partition
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bool partition_cut_requested_ = true;
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// true if it should cut the next filter partition block
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bool cut_filter_block = false;
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};
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} // namespace rocksdb
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