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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).
#pragma once
#ifndef ROCKSDB_LITE
#include <limits>
#include <string>
#include <vector>
#include "options/db_options.h"
#include "port/port.h"
#include "rocksdb/comparator.h"
#include "rocksdb/iterator.h"
#include "rocksdb/slice.h"
#include "rocksdb/status.h"
#include "rocksdb/utilities/write_batch_with_index.h"
namespace ROCKSDB_NAMESPACE {
class MergeContext;
struct Options;
// Key used by skip list, as the binary searchable index of WriteBatchWithIndex.
struct WriteBatchIndexEntry {
WriteBatchIndexEntry(size_t o, uint32_t c, size_t ko, size_t ksz)
: offset(o),
column_family(c),
key_offset(ko),
key_size(ksz),
search_key(nullptr) {}
// Create a dummy entry as the search key. This index entry won't be backed
// by an entry from the write batch, but a pointer to the search key. Or a
// special flag of offset can indicate we are seek to first.
// @_search_key: the search key
// @_column_family: column family
// @is_forward_direction: true for Seek(). False for SeekForPrev()
// @is_seek_to_first: true if we seek to the beginning of the column family
// _search_key should be null in this case.
WriteBatchIndexEntry(const Slice* _search_key, uint32_t _column_family,
bool is_forward_direction, bool is_seek_to_first)
// For SeekForPrev(), we need to make the dummy entry larger than any
// entry who has the same search key. Otherwise, we'll miss those entries.
: offset(is_forward_direction ? 0 : port::kMaxSizet),
column_family(_column_family),
key_offset(0),
key_size(is_seek_to_first ? kFlagMinInCf : 0),
search_key(_search_key) {
assert(_search_key != nullptr || is_seek_to_first);
}
// If this flag appears in the key_size, it indicates a
// key that is smaller than any other entry for the same column family.
static const size_t kFlagMinInCf = port::kMaxSizet;
bool is_min_in_cf() const {
assert(key_size != kFlagMinInCf ||
(key_offset == 0 && search_key == nullptr));
return key_size == kFlagMinInCf;
}
// offset of an entry in write batch's string buffer. If this is a dummy
// lookup key, in which case search_key != nullptr, offset is set to either
// 0 or max, only for comparison purpose. Because when entries have the same
// key, the entry with larger offset is larger, offset = 0 will make a seek
// key small or equal than all the entries with the seek key, so that Seek()
// will find all the entries of the same key. Similarly, offset = MAX will
// make the entry just larger than all entries with the search key so
// SeekForPrev() will see all the keys with the same key.
size_t offset;
uint32_t column_family; // c1olumn family of the entry.
size_t key_offset; // offset of the key in write batch's string buffer.
size_t key_size; // size of the key. kFlagMinInCf indicates
// that this is a dummy look up entry for
// SeekToFirst() to the beginning of the column
// family. We use the flag here to save a boolean
// in the struct.
const Slice* search_key; // if not null, instead of reading keys from
// write batch, use it to compare. This is used
// for lookup key.
};
class ReadableWriteBatch : public WriteBatch {
public:
explicit ReadableWriteBatch(size_t reserved_bytes = 0, size_t max_bytes = 0)
: WriteBatch(reserved_bytes, max_bytes) {}
// Retrieve some information from a write entry in the write batch, given
// the start offset of the write entry.
Status GetEntryFromDataOffset(size_t data_offset, WriteType* type, Slice* Key,
Slice* value, Slice* blob, Slice* xid) const;
};
class WriteBatchEntryComparator {
public:
WriteBatchEntryComparator(const Comparator* _default_comparator,
const ReadableWriteBatch* write_batch)
: default_comparator_(_default_comparator), write_batch_(write_batch) {}
// Compare a and b. Return a negative value if a is less than b, 0 if they
// are equal, and a positive value if a is greater than b
int operator()(const WriteBatchIndexEntry* entry1,
const WriteBatchIndexEntry* entry2) const;
int CompareKey(uint32_t column_family, const Slice& key1,
const Slice& key2) const;
void SetComparatorForCF(uint32_t column_family_id,
const Comparator* comparator) {
if (column_family_id >= cf_comparators_.size()) {
cf_comparators_.resize(column_family_id + 1, nullptr);
}
cf_comparators_[column_family_id] = comparator;
}
const Comparator* default_comparator() { return default_comparator_; }
private:
const Comparator* default_comparator_;
std::vector<const Comparator*> cf_comparators_;
const ReadableWriteBatch* write_batch_;
};
class WriteBatchWithIndexInternal {
public:
enum Result { kFound, kDeleted, kNotFound, kMergeInProgress, kError };
// If batch contains a value for key, store it in *value and return kFound.
// If batch contains a deletion for key, return Deleted.
// If batch contains Merge operations as the most recent entry for a key,
// and the merge process does not stop (not reaching a value or delete),
// prepend the current merge operands to *operands,
// and return kMergeInProgress
// If batch does not contain this key, return kNotFound
// Else, return kError on error with error Status stored in *s.
static WriteBatchWithIndexInternal::Result GetFromBatch(
const ImmutableDBOptions& ioptions, WriteBatchWithIndex* batch,
ColumnFamilyHandle* column_family, const Slice& key,
MergeContext* merge_context, WriteBatchEntryComparator* cmp,
std::string* value, bool overwrite_key, Status* s);
};
} // namespace ROCKSDB_NAMESPACE
#endif // !ROCKSDB_LITE
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