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rocksdb/table/table_builder.cc

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13 KiB

// Copyright (c) 2011 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.
#include "rocksdb/table_builder.h"
#include <assert.h>
#include <map>
#include "rocksdb/comparator.h"
#include "rocksdb/env.h"
#include "rocksdb/filter_policy.h"
#include "rocksdb/options.h"
#include "table/block_builder.h"
#include "table/filter_block.h"
#include "table/format.h"
#include "table/table.h"
#include "util/coding.h"
#include "util/crc32c.h"
#include "util/stop_watch.h"
namespace rocksdb {
namespace {
struct BytewiseLessThan {
bool operator()(const std::string& key1, const std::string& key2) {
// smaller entries will be placed in front.
return comparator->Compare(key1, key2) <= 0;
}
const Comparator* comparator = BytewiseComparator();
};
// When writing to a block that requires entries to be sorted by
// `BytewiseComparator`, we can buffer the content to `BytewiseSortedMap`
// before writng to store.
typedef std::map<std::string, std::string, BytewiseLessThan> BytewiseSortedMap;
void AddStats(BytewiseSortedMap& stats, std::string name, uint64_t val) {
assert(stats.find(name) == stats.end());
std::string dst;
PutVarint64(&dst, val);
stats.insert(
std::make_pair(name, dst)
);
}
static bool GoodCompressionRatio(size_t compressed_size, size_t raw_size) {
// Check to see if compressed less than 12.5%
return compressed_size < raw_size - (raw_size / 8u);
}
} // anonymous namespace
struct TableBuilder::Rep {
Options options;
Options index_block_options;
WritableFile* file;
uint64_t offset = 0;
Status status;
BlockBuilder data_block;
BlockBuilder index_block;
std::string last_key;
uint64_t num_entries = 0;
uint64_t num_data_blocks = 0;
uint64_t raw_key_size = 0;
uint64_t raw_value_size = 0;
uint64_t data_size = 0;
bool closed = false; // Either Finish() or Abandon() has been called.
FilterBlockBuilder* filter_block;
// We do not emit the index entry for a block until we have seen the
// first key for the next data block. This allows us to use shorter
// keys in the index block. For example, consider a block boundary
// between the keys "the quick brown fox" and "the who". We can use
// "the r" as the key for the index block entry since it is >= all
// entries in the first block and < all entries in subsequent
// blocks.
//
// Invariant: r->pending_index_entry is true only if data_block is empty.
bool pending_index_entry;
BlockHandle pending_handle; // Handle to add to index block
std::string compressed_output;
Rep(const Options& opt, WritableFile* f)
: options(opt),
index_block_options(opt),
file(f),
data_block(&options),
index_block(&index_block_options),
filter_block(opt.filter_policy == nullptr ? nullptr
: new FilterBlockBuilder(opt)),
pending_index_entry(false) {
index_block_options.block_restart_interval = 1;
}
};
TableBuilder::TableBuilder(const Options& options, WritableFile* file,
int level)
: rep_(new Rep(options, file)), level_(level) {
if (rep_->filter_block != nullptr) {
rep_->filter_block->StartBlock(0);
}
}
TableBuilder::~TableBuilder() {
assert(rep_->closed); // Catch errors where caller forgot to call Finish()
delete rep_->filter_block;
delete rep_;
}
Status TableBuilder::ChangeOptions(const Options& options) {
// Note: if more fields are added to Options, update
// this function to catch changes that should not be allowed to
// change in the middle of building a Table.
if (options.comparator != rep_->options.comparator) {
return Status::InvalidArgument("changing comparator while building table");
}
// Note that any live BlockBuilders point to rep_->options and therefore
// will automatically pick up the updated options.
rep_->options = options;
rep_->index_block_options = options;
rep_->index_block_options.block_restart_interval = 1;
return Status::OK();
}
void TableBuilder::Add(const Slice& key, const Slice& value) {
Rep* r = rep_;
assert(!r->closed);
if (!ok()) return;
if (r->num_entries > 0) {
assert(r->options.comparator->Compare(key, Slice(r->last_key)) > 0);
}
const size_t curr_size = r->data_block.CurrentSizeEstimate();
const size_t estimated_size_after = r->data_block.EstimateSizeAfterKV(key,
value);
// Do flush if one of the below two conditions is true:
// 1) if the current estimated size already exceeds the block size,
// 2) block_size_deviation is set and the estimated size after appending
// the kv will exceed the block size and the current size is under the
// the deviation.
if (curr_size >= r->options.block_size ||
(estimated_size_after > r->options.block_size &&
r->options.block_size_deviation > 0 &&
(curr_size * 100) >
r->options.block_size * (100 - r->options.block_size_deviation))) {
Flush();
}
if (r->pending_index_entry) {
assert(r->data_block.empty());
r->options.comparator->FindShortestSeparator(&r->last_key, key);
std::string handle_encoding;
r->pending_handle.EncodeTo(&handle_encoding);
r->index_block.Add(r->last_key, Slice(handle_encoding));
r->pending_index_entry = false;
}
if (r->filter_block != nullptr) {
r->filter_block->AddKey(key);
}
r->last_key.assign(key.data(), key.size());
r->data_block.Add(key, value);
r->num_entries++;
r->raw_key_size += key.size();
r->raw_value_size += value.size();
}
void TableBuilder::Flush() {
Rep* r = rep_;
assert(!r->closed);
if (!ok()) return;
if (r->data_block.empty()) return;
assert(!r->pending_index_entry);
WriteBlock(&r->data_block, &r->pending_handle);
if (ok()) {
r->pending_index_entry = true;
r->status = r->file->Flush();
}
if (r->filter_block != nullptr) {
r->filter_block->StartBlock(r->offset);
}
r->data_size = r->offset;
++r->num_data_blocks;
}
void TableBuilder::WriteBlock(BlockBuilder* block, BlockHandle* handle) {
// File format contains a sequence of blocks where each block has:
// block_data: uint8[n]
// type: uint8
// crc: uint32
assert(ok());
Rep* r = rep_;
Slice raw = block->Finish();
Slice block_contents;
std::string* compressed = &r->compressed_output;
CompressionType type;
// If the use has specified a different compression level for each level,
// then pick the compresison for that level.
if (!r->options.compression_per_level.empty()) {
const int n = r->options.compression_per_level.size();
// It is possible for level_ to be -1; in that case, we use level
// 0's compression. This occurs mostly in backwards compatibility
// situations when the builder doesn't know what level the file
// belongs to. Likewise, if level_ is beyond the end of the
// specified compression levels, use the last value.
type = r->options.compression_per_level[std::max(0, std::min(level_, n))];
} else {
type = r->options.compression;
}
switch (type) {
case kNoCompression:
block_contents = raw;
break;
case kSnappyCompression: {
std::string* compressed = &r->compressed_output;
if (port::Snappy_Compress(r->options.compression_opts, raw.data(),
raw.size(), compressed) &&
GoodCompressionRatio(compressed->size(), raw.size())) {
block_contents = *compressed;
} else {
// Snappy not supported, or not good compression ratio, so just
// store uncompressed form
block_contents = raw;
type = kNoCompression;
}
break;
}
case kZlibCompression:
if (port::Zlib_Compress(r->options.compression_opts, raw.data(),
raw.size(), compressed) &&
GoodCompressionRatio(compressed->size(), raw.size())) {
block_contents = *compressed;
} else {
// Zlib not supported, or not good compression ratio, so just
// store uncompressed form
block_contents = raw;
type = kNoCompression;
}
break;
case kBZip2Compression:
if (port::BZip2_Compress(r->options.compression_opts, raw.data(),
raw.size(), compressed) &&
GoodCompressionRatio(compressed->size(), raw.size())) {
block_contents = *compressed;
} else {
// BZip not supported, or not good compression ratio, so just
// store uncompressed form
block_contents = raw;
type = kNoCompression;
}
break;
}
WriteRawBlock(block_contents, type, handle);
r->compressed_output.clear();
block->Reset();
}
void TableBuilder::WriteRawBlock(const Slice& block_contents,
CompressionType type,
BlockHandle* handle) {
Rep* r = rep_;
StopWatch sw(r->options.env, r->options.statistics, WRITE_RAW_BLOCK_MICROS);
handle->set_offset(r->offset);
handle->set_size(block_contents.size());
r->status = r->file->Append(block_contents);
if (r->status.ok()) {
char trailer[kBlockTrailerSize];
trailer[0] = type;
uint32_t crc = crc32c::Value(block_contents.data(), block_contents.size());
crc = crc32c::Extend(crc, trailer, 1); // Extend crc to cover block type
EncodeFixed32(trailer+1, crc32c::Mask(crc));
r->status = r->file->Append(Slice(trailer, kBlockTrailerSize));
if (r->status.ok()) {
r->offset += block_contents.size() + kBlockTrailerSize;
}
}
}
Status TableBuilder::status() const {
return rep_->status;
}
Status TableBuilder::Finish() {
Rep* r = rep_;
Flush();
assert(!r->closed);
r->closed = true;
BlockHandle filter_block_handle, metaindex_block_handle, index_block_handle;
// Write filter block
if (ok() && r->filter_block != nullptr) {
WriteRawBlock(r->filter_block->Finish(), kNoCompression,
&filter_block_handle);
}
// To make sure stats block is able to keep the accurate size of index
// block, we will finish writing all index entries here and flush them
// to storage after metaindex block is written.
if (ok() && (r->pending_index_entry)) {
r->options.comparator->FindShortSuccessor(&r->last_key);
std::string handle_encoding;
r->pending_handle.EncodeTo(&handle_encoding);
r->index_block.Add(r->last_key, Slice(handle_encoding));
r->pending_index_entry = false;
}
// Write meta blocks and metaindex block with the following order.
// 1. [meta block: filter]
// 2. [meta block: stats]
// 3. [metaindex block]
if (ok()) {
// We use `BytewiseComparator` as the comparator for meta block.
BlockBuilder meta_index_block(
r->options.block_restart_interval,
BytewiseComparator()
);
// Key: meta block name
// Value: block handle to that meta block
BytewiseSortedMap meta_block_handles;
// Write filter block.
if (r->filter_block != nullptr) {
// Add mapping from "<filter_block_prefix>.Name" to location
// of filter data.
std::string key = Table::kFilterBlockPrefix;
key.append(r->options.filter_policy->Name());
std::string handle_encoding;
filter_block_handle.EncodeTo(&handle_encoding);
meta_block_handles.insert(
std::make_pair(key, handle_encoding)
);
}
// Write stats block.
{
BlockBuilder stats_block(
r->options.block_restart_interval,
BytewiseComparator()
);
BytewiseSortedMap stats;
// Add basic stats
AddStats(stats, TableStatsNames::kRawKeySize, r->raw_key_size);
AddStats(stats, TableStatsNames::kRawValueSize, r->raw_value_size);
AddStats(stats, TableStatsNames::kDataSize, r->data_size);
AddStats(
stats,
TableStatsNames::kIndexSize,
r->index_block.CurrentSizeEstimate() + kBlockTrailerSize
);
AddStats(stats, TableStatsNames::kNumEntries, r->num_entries);
AddStats(stats, TableStatsNames::kNumDataBlocks, r->num_data_blocks);
for (const auto& stat : stats) {
stats_block.Add(stat.first, stat.second);
}
BlockHandle stats_block_handle;
WriteBlock(&stats_block, &stats_block_handle);
std::string handle_encoding;
stats_block_handle.EncodeTo(&handle_encoding);
meta_block_handles.insert(
std::make_pair(Table::kStatsBlock, handle_encoding)
);
} // end of stats block writing
for (const auto& metablock : meta_block_handles) {
meta_index_block.Add(metablock.first, metablock.second);
}
WriteBlock(&meta_index_block, &metaindex_block_handle);
} // meta blocks and metaindex block.
// Write index block
if (ok()) {
WriteBlock(&r->index_block, &index_block_handle);
}
// Write footer
if (ok()) {
Footer footer;
footer.set_metaindex_handle(metaindex_block_handle);
footer.set_index_handle(index_block_handle);
std::string footer_encoding;
footer.EncodeTo(&footer_encoding);
r->status = r->file->Append(footer_encoding);
if (r->status.ok()) {
r->offset += footer_encoding.size();
}
}
return r->status;
}
void TableBuilder::Abandon() {
Rep* r = rep_;
assert(!r->closed);
r->closed = true;
}
uint64_t TableBuilder::NumEntries() const {
return rep_->num_entries;
}
uint64_t TableBuilder::FileSize() const {
return rep_->offset;
}
} // namespace rocksdb