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270 linhas
7.9 KiB
270 linhas
7.9 KiB
// 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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#include "leveldb/table_builder.h"
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#include <assert.h>
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#include "leveldb/comparator.h"
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#include "leveldb/env.h"
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#include "leveldb/filter_policy.h"
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#include "leveldb/options.h"
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#include "table/block_builder.h"
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#include "table/filter_block.h"
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#include "table/format.h"
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#include "util/coding.h"
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#include "util/crc32c.h"
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namespace leveldb {
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struct TableBuilder::Rep {
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Options options;
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Options index_block_options;
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WritableFile* file;
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uint64_t offset;
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Status status;
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BlockBuilder data_block;
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BlockBuilder index_block;
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std::string last_key;
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int64_t num_entries;
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bool closed; // Either Finish() or Abandon() has been called.
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FilterBlockBuilder* filter_block;
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// We do not emit the index entry for a block until we have seen the
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// first key for the next data block. This allows us to use shorter
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// keys in the index block. For example, consider a block boundary
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// between the keys "the quick brown fox" and "the who". We can use
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// "the r" as the key for the index block entry since it is >= all
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// entries in the first block and < all entries in subsequent
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// blocks.
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//
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// Invariant: r->pending_index_entry is true only if data_block is empty.
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bool pending_index_entry;
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BlockHandle pending_handle; // Handle to add to index block
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std::string compressed_output;
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Rep(const Options& opt, WritableFile* f)
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: options(opt),
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index_block_options(opt),
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file(f),
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offset(0),
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data_block(&options),
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index_block(&index_block_options),
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num_entries(0),
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closed(false),
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filter_block(opt.filter_policy == NULL ? NULL
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: new FilterBlockBuilder(opt.filter_policy)),
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pending_index_entry(false) {
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index_block_options.block_restart_interval = 1;
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}
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};
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TableBuilder::TableBuilder(const Options& options, WritableFile* file)
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: rep_(new Rep(options, file)) {
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if (rep_->filter_block != NULL) {
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rep_->filter_block->StartBlock(0);
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}
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}
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TableBuilder::~TableBuilder() {
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assert(rep_->closed); // Catch errors where caller forgot to call Finish()
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delete rep_->filter_block;
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delete rep_;
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}
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Status TableBuilder::ChangeOptions(const Options& options) {
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// Note: if more fields are added to Options, update
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// this function to catch changes that should not be allowed to
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// change in the middle of building a Table.
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if (options.comparator != rep_->options.comparator) {
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return Status::InvalidArgument("changing comparator while building table");
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}
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// Note that any live BlockBuilders point to rep_->options and therefore
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// will automatically pick up the updated options.
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rep_->options = options;
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rep_->index_block_options = options;
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rep_->index_block_options.block_restart_interval = 1;
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return Status::OK();
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}
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void TableBuilder::Add(const Slice& key, const Slice& value) {
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Rep* r = rep_;
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assert(!r->closed);
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if (!ok()) return;
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if (r->num_entries > 0) {
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assert(r->options.comparator->Compare(key, Slice(r->last_key)) > 0);
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}
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if (r->pending_index_entry) {
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assert(r->data_block.empty());
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r->options.comparator->FindShortestSeparator(&r->last_key, key);
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std::string handle_encoding;
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r->pending_handle.EncodeTo(&handle_encoding);
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r->index_block.Add(r->last_key, Slice(handle_encoding));
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r->pending_index_entry = false;
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}
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if (r->filter_block != NULL) {
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r->filter_block->AddKey(key);
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}
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r->last_key.assign(key.data(), key.size());
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r->num_entries++;
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r->data_block.Add(key, value);
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const size_t estimated_block_size = r->data_block.CurrentSizeEstimate();
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if (estimated_block_size >= r->options.block_size) {
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Flush();
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}
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}
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void TableBuilder::Flush() {
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Rep* r = rep_;
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assert(!r->closed);
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if (!ok()) return;
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if (r->data_block.empty()) return;
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assert(!r->pending_index_entry);
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WriteBlock(&r->data_block, &r->pending_handle);
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if (ok()) {
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r->pending_index_entry = true;
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r->status = r->file->Flush();
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}
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if (r->filter_block != NULL) {
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r->filter_block->StartBlock(r->offset);
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}
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}
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void TableBuilder::WriteBlock(BlockBuilder* block, BlockHandle* handle) {
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// File format contains a sequence of blocks where each block has:
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// block_data: uint8[n]
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// type: uint8
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// crc: uint32
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assert(ok());
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Rep* r = rep_;
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Slice raw = block->Finish();
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Slice block_contents;
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CompressionType type = r->options.compression;
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// TODO(postrelease): Support more compression options: zlib?
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switch (type) {
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case kNoCompression:
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block_contents = raw;
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break;
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case kSnappyCompression: {
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std::string* compressed = &r->compressed_output;
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if (port::Snappy_Compress(raw.data(), raw.size(), compressed) &&
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compressed->size() < raw.size() - (raw.size() / 8u)) {
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block_contents = *compressed;
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} else {
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// Snappy not supported, or compressed less than 12.5%, so just
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// store uncompressed form
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block_contents = raw;
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type = kNoCompression;
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}
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break;
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}
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}
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WriteRawBlock(block_contents, type, handle);
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r->compressed_output.clear();
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block->Reset();
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}
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void TableBuilder::WriteRawBlock(const Slice& block_contents,
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CompressionType type,
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BlockHandle* handle) {
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Rep* r = rep_;
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handle->set_offset(r->offset);
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handle->set_size(block_contents.size());
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r->status = r->file->Append(block_contents);
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if (r->status.ok()) {
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char trailer[kBlockTrailerSize];
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trailer[0] = type;
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uint32_t crc = crc32c::Value(block_contents.data(), block_contents.size());
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crc = crc32c::Extend(crc, trailer, 1); // Extend crc to cover block type
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EncodeFixed32(trailer+1, crc32c::Mask(crc));
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r->status = r->file->Append(Slice(trailer, kBlockTrailerSize));
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if (r->status.ok()) {
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r->offset += block_contents.size() + kBlockTrailerSize;
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}
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}
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}
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Status TableBuilder::status() const {
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return rep_->status;
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}
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Status TableBuilder::Finish() {
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Rep* r = rep_;
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Flush();
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assert(!r->closed);
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r->closed = true;
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BlockHandle filter_block_handle, metaindex_block_handle, index_block_handle;
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// Write filter block
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if (ok() && r->filter_block != NULL) {
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WriteRawBlock(r->filter_block->Finish(), kNoCompression,
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&filter_block_handle);
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}
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// Write metaindex block
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if (ok()) {
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BlockBuilder meta_index_block(&r->options);
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if (r->filter_block != NULL) {
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// Add mapping from "filter.Name" to location of filter data
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std::string key = "filter.";
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key.append(r->options.filter_policy->Name());
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std::string handle_encoding;
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filter_block_handle.EncodeTo(&handle_encoding);
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meta_index_block.Add(key, handle_encoding);
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}
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// TODO(postrelease): Add stats and other meta blocks
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WriteBlock(&meta_index_block, &metaindex_block_handle);
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}
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// Write index block
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if (ok()) {
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if (r->pending_index_entry) {
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r->options.comparator->FindShortSuccessor(&r->last_key);
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std::string handle_encoding;
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r->pending_handle.EncodeTo(&handle_encoding);
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r->index_block.Add(r->last_key, Slice(handle_encoding));
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r->pending_index_entry = false;
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}
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WriteBlock(&r->index_block, &index_block_handle);
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}
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// Write footer
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if (ok()) {
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Footer footer;
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footer.set_metaindex_handle(metaindex_block_handle);
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footer.set_index_handle(index_block_handle);
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std::string footer_encoding;
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footer.EncodeTo(&footer_encoding);
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r->status = r->file->Append(footer_encoding);
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if (r->status.ok()) {
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r->offset += footer_encoding.size();
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}
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}
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return r->status;
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}
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void TableBuilder::Abandon() {
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Rep* r = rep_;
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assert(!r->closed);
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r->closed = true;
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}
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uint64_t TableBuilder::NumEntries() const {
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return rep_->num_entries;
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}
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uint64_t TableBuilder::FileSize() const {
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return rep_->offset;
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}
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} // namespace leveldb
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