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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
//
// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
//
// A filter block is stored near the end of a Table file. It contains
// filters (e.g., bloom filters) for all data blocks in the table combined
// into a single filter block.
//
// It is a base class for BlockBasedFilter and FullFilter.
// These two are both used in BlockBasedTable. The first one contain filter
// For a part of keys in sst file, the second contain filter for all keys
// in sst file.
#pragma once
#include <stddef.h>
#include <stdint.h>
#include <memory>
#include <string>
#include <vector>
#include "db/dbformat.h"
#include "rocksdb/options.h"
#include "rocksdb/slice.h"
#include "rocksdb/slice_transform.h"
#include "rocksdb/table.h"
#include "table/format.h"
#include "table/multiget_context.h"
#include "trace_replay/block_cache_tracer.h"
#include "util/hash.h"
namespace ROCKSDB_NAMESPACE {
const uint64_t kNotValid = ULLONG_MAX;
class FilterPolicy;
class GetContext;
using MultiGetRange = MultiGetContext::Range;
// A FilterBlockBuilder is used to construct all of the filters for a
// particular Table. It generates a single string which is stored as
// a special block in the Table.
//
// The sequence of calls to FilterBlockBuilder must match the regexp:
// (StartBlock Add*)* Finish
//
// BlockBased/Full FilterBlock would be called in the same way.
class FilterBlockBuilder {
public:
explicit FilterBlockBuilder() {}
// No copying allowed
FilterBlockBuilder(const FilterBlockBuilder&) = delete;
void operator=(const FilterBlockBuilder&) = delete;
virtual ~FilterBlockBuilder() {}
virtual bool IsBlockBased() = 0; // If is blockbased filter
virtual void StartBlock(uint64_t block_offset) = 0; // Start new block filter
virtual void Add(const Slice& key) = 0; // Add a key to current filter
virtual size_t NumAdded() const = 0; // Number of keys added
Slice Finish() { // Generate Filter
const BlockHandle empty_handle;
Status dont_care_status;
auto ret = Finish(empty_handle, &dont_care_status);
assert(dont_care_status.ok());
return ret;
}
virtual Slice Finish(const BlockHandle& tmp, Status* status) = 0;
};
// A FilterBlockReader is used to parse filter from SST table.
// KeyMayMatch and PrefixMayMatch would trigger filter checking
//
// BlockBased/Full FilterBlock would be called in the same way.
class FilterBlockReader {
public:
FilterBlockReader() = default;
virtual ~FilterBlockReader() = default;
FilterBlockReader(const FilterBlockReader&) = delete;
FilterBlockReader& operator=(const FilterBlockReader&) = delete;
virtual bool IsBlockBased() = 0; // If is blockbased filter
/**
* If no_io is set, then it returns true if it cannot answer the query without
* reading data from disk. This is used in PartitionedFilterBlockReader to
* avoid reading partitions that are not in block cache already
*
* Normally filters are built on only the user keys and the InternalKey is not
* needed for a query. The index in PartitionedFilterBlockReader however is
* built upon InternalKey and must be provided via const_ikey_ptr when running
* queries.
*/
virtual bool KeyMayMatch(const Slice& key,
const SliceTransform* prefix_extractor,
uint64_t block_offset, const bool no_io,
const Slice* const const_ikey_ptr,
GetContext* get_context,
BlockCacheLookupContext* lookup_context) = 0;
virtual void KeysMayMatch(MultiGetRange* range,
const SliceTransform* prefix_extractor,
uint64_t block_offset, const bool no_io,
BlockCacheLookupContext* lookup_context) {
for (auto iter = range->begin(); iter != range->end(); ++iter) {
const Slice ukey = iter->ukey;
const Slice ikey = iter->ikey;
GetContext* const get_context = iter->get_context;
if (!KeyMayMatch(ukey, prefix_extractor, block_offset, no_io, &ikey,
get_context, lookup_context)) {
range->SkipKey(iter);
}
}
}
/**
* no_io and const_ikey_ptr here means the same as in KeyMayMatch
*/
virtual bool PrefixMayMatch(const Slice& prefix,
const SliceTransform* prefix_extractor,
uint64_t block_offset, const bool no_io,
const Slice* const const_ikey_ptr,
GetContext* get_context,
BlockCacheLookupContext* lookup_context) = 0;
virtual void PrefixesMayMatch(MultiGetRange* range,
const SliceTransform* prefix_extractor,
uint64_t block_offset, const bool no_io,
BlockCacheLookupContext* lookup_context) {
for (auto iter = range->begin(); iter != range->end(); ++iter) {
const Slice ukey = iter->ukey;
const Slice ikey = iter->ikey;
GetContext* const get_context = iter->get_context;
if (prefix_extractor->InDomain(ukey) &&
!PrefixMayMatch(prefix_extractor->Transform(ukey), prefix_extractor,
block_offset, no_io, &ikey, get_context,
lookup_context)) {
range->SkipKey(iter);
}
}
}
virtual size_t ApproximateMemoryUsage() const = 0;
// convert this object to a human readable form
virtual std::string ToString() const {
std::string error_msg("Unsupported filter \n");
return error_msg;
}
virtual void CacheDependencies(bool /*pin*/) {}
virtual bool RangeMayExist(const Slice* /*iterate_upper_bound*/,
const Slice& user_key,
const SliceTransform* prefix_extractor,
const Comparator* /*comparator*/,
const Slice* const const_ikey_ptr,
bool* filter_checked, bool need_upper_bound_check,
BlockCacheLookupContext* lookup_context) {
if (need_upper_bound_check) {
return true;
}
*filter_checked = true;
Slice prefix = prefix_extractor->Transform(user_key);
return PrefixMayMatch(prefix, prefix_extractor, kNotValid, false,
const_ikey_ptr, /* get_context */ nullptr,
lookup_context);
}
};
} // namespace ROCKSDB_NAMESPACE
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