Summary: Add a new option ReadOptions.auto_prefix_mode. When set to true, iterator should return the same result as total order seek, but may choose to do prefix seek internally, based on iterator upper bounds. Also fix two previous bugs when handling prefix extrator changes: (1) reverse iterator should not rely on upper bound to determine prefix. Fix it with skipping prefix check. (2) block-based filter is not handled properly. Pull Request resolved: https://github.com/facebook/rocksdb/pull/6314 Test Plan: (1) add a unit test; (2) add the check to stress test and run see whether it can pass at least one run. Differential Revision: D19458717 fbshipit-source-id: 51c1bcc5cdd826c2469af201979a39600e779bce
177 lines
6.8 KiB
C++
177 lines
6.8 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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//
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// Copyright (c) 2012 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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//
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// A filter block is stored near the end of a Table file. It contains
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// filters (e.g., bloom filters) for all data blocks in the table combined
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// into a single filter block.
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//
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// It is a base class for BlockBasedFilter and FullFilter.
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// These two are both used in BlockBasedTable. The first one contain filter
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// For a part of keys in sst file, the second contain filter for all keys
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// in sst file.
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#pragma once
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#include <stddef.h>
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#include <stdint.h>
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#include <memory>
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#include <string>
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#include <vector>
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#include "db/dbformat.h"
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#include "rocksdb/options.h"
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#include "rocksdb/slice.h"
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#include "rocksdb/slice_transform.h"
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#include "rocksdb/table.h"
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#include "table/format.h"
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#include "table/multiget_context.h"
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#include "trace_replay/block_cache_tracer.h"
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#include "util/hash.h"
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namespace rocksdb {
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const uint64_t kNotValid = ULLONG_MAX;
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class FilterPolicy;
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class GetContext;
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using MultiGetRange = MultiGetContext::Range;
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// A FilterBlockBuilder is used to construct all of the filters for a
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// particular Table. It generates a single string which is stored as
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// a special block in the Table.
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//
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// The sequence of calls to FilterBlockBuilder must match the regexp:
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// (StartBlock Add*)* Finish
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//
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// BlockBased/Full FilterBlock would be called in the same way.
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class FilterBlockBuilder {
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public:
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explicit FilterBlockBuilder() {}
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// No copying allowed
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FilterBlockBuilder(const FilterBlockBuilder&) = delete;
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void operator=(const FilterBlockBuilder&) = delete;
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virtual ~FilterBlockBuilder() {}
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virtual bool IsBlockBased() = 0; // If is blockbased filter
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virtual void StartBlock(uint64_t block_offset) = 0; // Start new block filter
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virtual void Add(const Slice& key) = 0; // Add a key to current filter
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virtual size_t NumAdded() const = 0; // Number of keys added
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Slice Finish() { // Generate Filter
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const BlockHandle empty_handle;
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Status dont_care_status;
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auto ret = Finish(empty_handle, &dont_care_status);
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assert(dont_care_status.ok());
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return ret;
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}
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virtual Slice Finish(const BlockHandle& tmp, Status* status) = 0;
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};
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// A FilterBlockReader is used to parse filter from SST table.
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// KeyMayMatch and PrefixMayMatch would trigger filter checking
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//
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// BlockBased/Full FilterBlock would be called in the same way.
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class FilterBlockReader {
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public:
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FilterBlockReader() = default;
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virtual ~FilterBlockReader() = default;
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FilterBlockReader(const FilterBlockReader&) = delete;
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FilterBlockReader& operator=(const FilterBlockReader&) = delete;
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virtual bool IsBlockBased() = 0; // If is blockbased filter
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/**
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* If no_io is set, then it returns true if it cannot answer the query without
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* reading data from disk. This is used in PartitionedFilterBlockReader to
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* avoid reading partitions that are not in block cache already
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*
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* Normally filters are built on only the user keys and the InternalKey is not
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* needed for a query. The index in PartitionedFilterBlockReader however is
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* built upon InternalKey and must be provided via const_ikey_ptr when running
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* queries.
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*/
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virtual bool KeyMayMatch(const Slice& key,
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const SliceTransform* prefix_extractor,
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uint64_t block_offset, const bool no_io,
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const Slice* const const_ikey_ptr,
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GetContext* get_context,
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BlockCacheLookupContext* lookup_context) = 0;
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virtual void KeysMayMatch(MultiGetRange* range,
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const SliceTransform* prefix_extractor,
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uint64_t block_offset, const bool no_io,
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BlockCacheLookupContext* lookup_context) {
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for (auto iter = range->begin(); iter != range->end(); ++iter) {
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const Slice ukey = iter->ukey;
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const Slice ikey = iter->ikey;
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GetContext* const get_context = iter->get_context;
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if (!KeyMayMatch(ukey, prefix_extractor, block_offset, no_io, &ikey,
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get_context, lookup_context)) {
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range->SkipKey(iter);
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}
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}
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}
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/**
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* no_io and const_ikey_ptr here means the same as in KeyMayMatch
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*/
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virtual bool PrefixMayMatch(const Slice& prefix,
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const SliceTransform* prefix_extractor,
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uint64_t block_offset, const bool no_io,
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const Slice* const const_ikey_ptr,
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GetContext* get_context,
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BlockCacheLookupContext* lookup_context) = 0;
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virtual void PrefixesMayMatch(MultiGetRange* range,
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const SliceTransform* prefix_extractor,
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uint64_t block_offset, const bool no_io,
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BlockCacheLookupContext* lookup_context) {
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for (auto iter = range->begin(); iter != range->end(); ++iter) {
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const Slice ukey = iter->ukey;
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const Slice ikey = iter->ikey;
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GetContext* const get_context = iter->get_context;
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if (prefix_extractor->InDomain(ukey) &&
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!PrefixMayMatch(prefix_extractor->Transform(ukey), prefix_extractor,
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block_offset, no_io, &ikey, get_context,
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lookup_context)) {
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range->SkipKey(iter);
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}
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}
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}
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virtual size_t ApproximateMemoryUsage() const = 0;
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// convert this object to a human readable form
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virtual std::string ToString() const {
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std::string error_msg("Unsupported filter \n");
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return error_msg;
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}
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virtual void CacheDependencies(bool /*pin*/) {}
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virtual bool RangeMayExist(const Slice* /*iterate_upper_bound*/,
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const Slice& user_key,
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const SliceTransform* prefix_extractor,
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const Comparator* /*comparator*/,
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const Slice* const const_ikey_ptr,
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bool* filter_checked, bool need_upper_bound_check,
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BlockCacheLookupContext* lookup_context) {
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if (need_upper_bound_check) {
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return true;
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}
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*filter_checked = true;
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Slice prefix = prefix_extractor->Transform(user_key);
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return PrefixMayMatch(prefix, prefix_extractor, kNotValid, false,
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const_ikey_ptr, /* get_context */ nullptr,
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lookup_context);
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}
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};
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} // namespace rocksdb
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