--- /dev/null
+#include "database-builder.h"
+
+#include "dprintf.h"
+#include "turbopfor-encode.h"
+
+#include <algorithm>
+#include <assert.h>
+#include <fcntl.h>
+#include <string.h>
+#include <string_view>
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <zdict.h>
+#include <zstd.h>
+
+#define P4NENC_BOUND(n) ((n + 127) / 128 + (n + 32) * sizeof(uint32_t))
+
+#define NUM_TRIGRAMS 16777216
+
+using namespace std;
+using namespace std::chrono;
+
+constexpr unsigned num_overflow_slots = 16;
+
+string zstd_compress(const string &src, ZSTD_CDict *cdict, string *tempbuf);
+
+static inline uint32_t read_unigram(const string_view s, size_t idx)
+{
+ if (idx < s.size()) {
+ return (unsigned char)s[idx];
+ } else {
+ return 0;
+ }
+}
+
+static inline uint32_t read_trigram(const string_view s, size_t start)
+{
+ return read_unigram(s, start) |
+ (read_unigram(s, start + 1) << 8) |
+ (read_unigram(s, start + 2) << 16);
+}
+
+class PostingListBuilder {
+public:
+ inline void add_docid(uint32_t docid);
+ void finish();
+
+ string encoded;
+ size_t num_docids = 0;
+
+private:
+ void write_header(uint32_t docid);
+ void append_block();
+
+ vector<uint32_t> pending_deltas;
+
+ uint32_t last_block_end, last_docid = -1;
+};
+
+void PostingListBuilder::add_docid(uint32_t docid)
+{
+ // Deduplicate against the last inserted value, if any.
+ if (docid == last_docid) {
+ return;
+ }
+
+ if (num_docids == 0) {
+ // Very first docid.
+ write_header(docid);
+ ++num_docids;
+ last_block_end = last_docid = docid;
+ return;
+ }
+
+ pending_deltas.push_back(docid - last_docid - 1);
+ last_docid = docid;
+ if (pending_deltas.size() == 128) {
+ append_block();
+ pending_deltas.clear();
+ last_block_end = docid;
+ }
+ ++num_docids;
+}
+
+void PostingListBuilder::finish()
+{
+ if (pending_deltas.empty()) {
+ return;
+ }
+
+ assert(!encoded.empty()); // write_header() should already have run.
+
+ // No interleaving for partial blocks.
+ unsigned char buf[P4NENC_BOUND(128)];
+ unsigned char *end = encode_pfor_single_block<128>(pending_deltas.data(), pending_deltas.size(), /*interleaved=*/false, buf);
+ encoded.append(reinterpret_cast<char *>(buf), reinterpret_cast<char *>(end));
+}
+
+void PostingListBuilder::append_block()
+{
+ unsigned char buf[P4NENC_BOUND(128)];
+ assert(pending_deltas.size() == 128);
+ unsigned char *end = encode_pfor_single_block<128>(pending_deltas.data(), 128, /*interleaved=*/true, buf);
+ encoded.append(reinterpret_cast<char *>(buf), reinterpret_cast<char *>(end));
+}
+
+void PostingListBuilder::write_header(uint32_t docid)
+{
+ unsigned char buf[P4NENC_BOUND(1)];
+ unsigned char *end = write_baseval(docid, buf);
+ encoded.append(reinterpret_cast<char *>(buf), end - buf);
+}
+
+void DictionaryBuilder::add_file(string filename)
+{
+ if (keep_current_block) { // Only bother saving the filenames if we're actually keeping the block.
+ if (!current_block.empty()) {
+ current_block.push_back('\0');
+ }
+ current_block += filename;
+ }
+ if (++num_files_in_block == block_size) {
+ flush_block();
+ }
+}
+
+void DictionaryBuilder::flush_block()
+{
+ if (keep_current_block) {
+ if (slot_for_current_block == -1) {
+ lengths.push_back(current_block.size());
+ sampled_blocks.push_back(move(current_block));
+ } else {
+ lengths[slot_for_current_block] = current_block.size();
+ sampled_blocks[slot_for_current_block] = move(current_block);
+ }
+ }
+ current_block.clear();
+ num_files_in_block = 0;
+ ++block_num;
+
+ if (block_num < blocks_to_keep) {
+ keep_current_block = true;
+ slot_for_current_block = -1;
+ } else {
+ // Keep every block with equal probability (reservoir sampling).
+ uint64_t idx = uniform_int_distribution<uint64_t>(0, block_num)(reservoir_rand);
+ keep_current_block = (idx < blocks_to_keep);
+ slot_for_current_block = idx;
+ }
+}
+
+string DictionaryBuilder::train(size_t buf_size)
+{
+ string dictionary_buf;
+ sort(sampled_blocks.begin(), sampled_blocks.end()); // Seemingly important for decompression speed.
+ for (const string &block : sampled_blocks) {
+ dictionary_buf += block;
+ }
+
+ string buf;
+ buf.resize(buf_size);
+ size_t ret = ZDICT_trainFromBuffer(&buf[0], buf_size, dictionary_buf.data(), lengths.data(), lengths.size());
+ if (ret == size_t(-1)) {
+ return "";
+ }
+ dprintf("Sampled %zu bytes in %zu blocks, built a dictionary of size %zu\n", dictionary_buf.size(), lengths.size(), ret);
+ buf.resize(ret);
+
+ sampled_blocks.clear();
+ lengths.clear();
+
+ return buf;
+}
+
+Corpus::Corpus(FILE *outfp, size_t block_size, ZSTD_CDict *cdict)
+ : invindex(new PostingListBuilder *[NUM_TRIGRAMS]), outfp(outfp), block_size(block_size), cdict(cdict)
+{
+ fill(invindex.get(), invindex.get() + NUM_TRIGRAMS, nullptr);
+}
+
+Corpus::~Corpus()
+{
+ for (unsigned i = 0; i < NUM_TRIGRAMS; ++i) {
+ delete invindex[i];
+ }
+}
+
+PostingListBuilder &Corpus::get_pl_builder(uint32_t trgm)
+{
+ if (invindex[trgm] == nullptr) {
+ invindex[trgm] = new PostingListBuilder;
+ }
+ return *invindex[trgm];
+}
+
+void Corpus::add_file(string filename)
+{
+ ++num_files;
+ if (!current_block.empty()) {
+ current_block.push_back('\0');
+ }
+ current_block += filename;
+ if (++num_files_in_block == block_size) {
+ flush_block();
+ }
+}
+
+void Corpus::flush_block()
+{
+ if (current_block.empty()) {
+ return;
+ }
+
+ uint32_t docid = num_blocks;
+
+ // Create trigrams.
+ const char *ptr = current_block.c_str();
+ while (ptr < current_block.c_str() + current_block.size()) {
+ string_view s(ptr);
+ if (s.size() >= 3) {
+ for (size_t j = 0; j < s.size() - 2; ++j) {
+ uint32_t trgm = read_trigram(s, j);
+ get_pl_builder(trgm).add_docid(docid);
+ }
+ }
+ ptr += s.size() + 1;
+ }
+
+ // Compress and add the filename block.
+ filename_blocks.push_back(ftell(outfp));
+ string compressed = zstd_compress(current_block, cdict, &tempbuf);
+ if (fwrite(compressed.data(), compressed.size(), 1, outfp) != 1) {
+ perror("fwrite()");
+ exit(1);
+ }
+
+ current_block.clear();
+ num_files_in_block = 0;
+ ++num_blocks;
+}
+
+void Corpus::finish()
+{
+ flush_block();
+ string tempbuf;
+ string compressed = zstd_compress(directory_data, nullptr, &tempbuf);
+ fprintf(stderr, "dirdata: %zu bytes (compressed: %zu)\n", directory_data.size(), compressed.size());
+}
+
+size_t Corpus::num_trigrams() const
+{
+ size_t num = 0;
+ for (unsigned trgm = 0; trgm < NUM_TRIGRAMS; ++trgm) {
+ if (invindex[trgm] != nullptr) {
+ ++num;
+ }
+ }
+ return num;
+}
+
+string zstd_compress(const string &src, ZSTD_CDict *cdict, string *tempbuf)
+{
+ static ZSTD_CCtx *ctx = nullptr;
+ if (ctx == nullptr) {
+ ctx = ZSTD_createCCtx();
+ }
+
+ size_t max_size = ZSTD_compressBound(src.size());
+ if (tempbuf->size() < max_size) {
+ tempbuf->resize(max_size);
+ }
+ size_t size;
+ if (cdict == nullptr) {
+ size = ZSTD_compressCCtx(ctx, &(*tempbuf)[0], max_size, src.data(), src.size(), /*level=*/6);
+ } else {
+ size = ZSTD_compress_usingCDict(ctx, &(*tempbuf)[0], max_size, src.data(), src.size(), cdict);
+ }
+ return string(tempbuf->data(), size);
+}
+
+bool is_prime(uint32_t x)
+{
+ if ((x % 2) == 0 || (x % 3) == 0) {
+ return false;
+ }
+ uint32_t limit = ceil(sqrt(x));
+ for (uint32_t factor = 5; factor <= limit; ++factor) {
+ if ((x % factor) == 0) {
+ return false;
+ }
+ }
+ return true;
+}
+
+uint32_t next_prime(uint32_t x)
+{
+ if ((x % 2) == 0) {
+ ++x;
+ }
+ while (!is_prime(x)) {
+ x += 2;
+ }
+ return x;
+}
+
+unique_ptr<Trigram[]> create_hashtable(Corpus &corpus, const vector<uint32_t> &all_trigrams, uint32_t ht_size, uint32_t num_overflow_slots)
+{
+ unique_ptr<Trigram[]> ht(new Trigram[ht_size + num_overflow_slots + 1]); // 1 for the sentinel element at the end.
+ for (unsigned i = 0; i < ht_size + num_overflow_slots + 1; ++i) {
+ ht[i].trgm = uint32_t(-1);
+ ht[i].num_docids = 0;
+ ht[i].offset = 0;
+ }
+ for (uint32_t trgm : all_trigrams) {
+ // We don't know offset yet, so set it to zero.
+ Trigram to_insert{ trgm, uint32_t(corpus.get_pl_builder(trgm).num_docids), 0 };
+
+ uint32_t bucket = hash_trigram(trgm, ht_size);
+ unsigned distance = 0;
+ while (ht[bucket].num_docids != 0) {
+ // Robin Hood hashing; reduces the longest distance by a lot.
+ unsigned other_distance = bucket - hash_trigram(ht[bucket].trgm, ht_size);
+ if (distance > other_distance) {
+ swap(to_insert, ht[bucket]);
+ distance = other_distance;
+ }
+
+ ++bucket, ++distance;
+ if (distance > num_overflow_slots) {
+ return nullptr;
+ }
+ }
+ ht[bucket] = to_insert;
+ }
+ return ht;
+}
+
+DatabaseBuilder::DatabaseBuilder(const char *outfile, int block_size, string dictionary)
+ : block_size(block_size)
+{
+ umask(0027);
+ outfp = fopen(outfile, "wb");
+ if (outfp == nullptr) {
+ perror(outfile);
+ exit(1);
+ }
+
+ // Write the header.
+ memcpy(hdr.magic, "\0plocate", 8);
+ hdr.version = -1; // Mark as broken.
+ hdr.hashtable_size = 0; // Not known yet.
+ hdr.extra_ht_slots = num_overflow_slots;
+ hdr.num_docids = 0;
+ hdr.hash_table_offset_bytes = -1; // We don't know these offsets yet.
+ hdr.max_version = 1;
+ hdr.filename_index_offset_bytes = -1;
+ hdr.zstd_dictionary_length_bytes = -1;
+ fwrite(&hdr, sizeof(hdr), 1, outfp);
+
+ if (dictionary.empty()) {
+ hdr.zstd_dictionary_offset_bytes = 0;
+ hdr.zstd_dictionary_length_bytes = 0;
+ } else {
+ hdr.zstd_dictionary_offset_bytes = ftell(outfp);
+ fwrite(dictionary.data(), dictionary.size(), 1, outfp);
+ hdr.zstd_dictionary_length_bytes = dictionary.size();
+ cdict = ZSTD_createCDict(dictionary.data(), dictionary.size(), /*level=*/6);
+ }
+}
+
+Corpus *DatabaseBuilder::start_corpus()
+{
+ corpus_start = steady_clock::now();
+ corpus = new Corpus(outfp, block_size, cdict);
+ return corpus;
+}
+
+void DatabaseBuilder::finish_corpus()
+{
+ corpus->finish();
+ hdr.num_docids = corpus->filename_blocks.size();
+
+ // Stick an empty block at the end as sentinel.
+ corpus->filename_blocks.push_back(ftell(outfp));
+ const size_t bytes_for_filenames = corpus->filename_blocks.back() - corpus->filename_blocks.front();
+
+ // Write the offsets to the filenames.
+ hdr.filename_index_offset_bytes = ftell(outfp);
+ const size_t bytes_for_filename_index = corpus->filename_blocks.size() * sizeof(uint64_t);
+ fwrite(corpus->filename_blocks.data(), corpus->filename_blocks.size(), sizeof(uint64_t), outfp);
+ corpus->filename_blocks.clear();
+ corpus->filename_blocks.shrink_to_fit();
+
+ // Finish up encoding the posting lists.
+ size_t trigrams = 0, longest_posting_list = 0;
+ size_t bytes_for_posting_lists = 0;
+ for (unsigned trgm = 0; trgm < NUM_TRIGRAMS; ++trgm) {
+ if (!corpus->seen_trigram(trgm))
+ continue;
+ PostingListBuilder &pl_builder = corpus->get_pl_builder(trgm);
+ pl_builder.finish();
+ longest_posting_list = max(longest_posting_list, pl_builder.num_docids);
+ trigrams += pl_builder.num_docids;
+ bytes_for_posting_lists += pl_builder.encoded.size();
+ }
+ size_t num_trigrams = corpus->num_trigrams();
+ dprintf("%zu files, %zu different trigrams, %zu entries, avg len %.2f, longest %zu\n",
+ corpus->num_files, num_trigrams, trigrams, double(trigrams) / num_trigrams, longest_posting_list);
+ dprintf("%zu bytes used for posting lists (%.2f bits/entry)\n", bytes_for_posting_lists, 8 * bytes_for_posting_lists / double(trigrams));
+
+ dprintf("Building posting lists took %.1f ms.\n\n", 1e3 * duration<float>(steady_clock::now() - corpus_start).count());
+
+ // Find the used trigrams.
+ vector<uint32_t> all_trigrams;
+ for (unsigned trgm = 0; trgm < NUM_TRIGRAMS; ++trgm) {
+ if (corpus->seen_trigram(trgm)) {
+ all_trigrams.push_back(trgm);
+ }
+ }
+
+ // Create the hash table.
+ unique_ptr<Trigram[]> hashtable;
+ uint32_t ht_size = next_prime(all_trigrams.size());
+ for (;;) {
+ hashtable = create_hashtable(*corpus, all_trigrams, ht_size, num_overflow_slots);
+ if (hashtable == nullptr) {
+ dprintf("Failed creating hash table of size %u, increasing by 5%% and trying again.\n", ht_size);
+ ht_size = next_prime(ht_size * 1.05);
+ } else {
+ dprintf("Created hash table of size %u.\n\n", ht_size);
+ break;
+ }
+ }
+
+ // Find the offsets for each posting list.
+ size_t bytes_for_hashtable = (ht_size + num_overflow_slots + 1) * sizeof(Trigram);
+ uint64_t offset = ftell(outfp) + bytes_for_hashtable;
+ for (unsigned i = 0; i < ht_size + num_overflow_slots + 1; ++i) {
+ hashtable[i].offset = offset; // Needs to be there even for empty slots.
+ if (hashtable[i].num_docids == 0) {
+ continue;
+ }
+
+ const string &encoded = corpus->get_pl_builder(hashtable[i].trgm).encoded;
+ offset += encoded.size();
+ }
+
+ // Write the hash table.
+ hdr.hash_table_offset_bytes = ftell(outfp);
+ hdr.hashtable_size = ht_size;
+ fwrite(hashtable.get(), ht_size + num_overflow_slots + 1, sizeof(Trigram), outfp);
+
+ // Write the actual posting lists.
+ for (unsigned i = 0; i < ht_size + num_overflow_slots + 1; ++i) {
+ if (hashtable[i].num_docids == 0) {
+ continue;
+ }
+ const string &encoded = corpus->get_pl_builder(hashtable[i].trgm).encoded;
+ fwrite(encoded.data(), encoded.size(), 1, outfp);
+ }
+
+ // Rewind, and write the updated header.
+ hdr.version = 1;
+ fseek(outfp, 0, SEEK_SET);
+ fwrite(&hdr, sizeof(hdr), 1, outfp);
+ fclose(outfp);
+
+ size_t total_bytes = (bytes_for_hashtable + bytes_for_posting_lists + bytes_for_filename_index + bytes_for_filenames);
+
+ dprintf("Block size: %7d files\n", block_size);
+ dprintf("Dictionary: %'7.1f MB\n", hdr.zstd_dictionary_length_bytes / 1048576.0);
+ dprintf("Hash table: %'7.1f MB\n", bytes_for_hashtable / 1048576.0);
+ dprintf("Posting lists: %'7.1f MB\n", bytes_for_posting_lists / 1048576.0);
+ dprintf("Filename index: %'7.1f MB\n", bytes_for_filename_index / 1048576.0);
+ dprintf("Filenames: %'7.1f MB\n", bytes_for_filenames / 1048576.0);
+ dprintf("Total: %'7.1f MB\n", total_bytes / 1048576.0);
+ dprintf("\n");
+}
--- /dev/null
+#ifndef _DATABASE_BUILDER_H
+#define _DATABASE_BUILDER_H 1
+
+#include "db.h"
+
+#include <chrono>
+#include <memory>
+#include <random>
+#include <stddef.h>
+#include <string>
+#include <vector>
+#include <zstd.h>
+
+class PostingListBuilder;
+
+class DatabaseReceiver {
+public:
+ virtual ~DatabaseReceiver() = default;
+ virtual void add_file(std::string filename) = 0;
+ virtual void flush_block() = 0;
+ virtual void finish() { flush_block(); }
+};
+
+class DictionaryBuilder : public DatabaseReceiver {
+public:
+ DictionaryBuilder(size_t blocks_to_keep, size_t block_size)
+ : blocks_to_keep(blocks_to_keep), block_size(block_size) {}
+ void add_file(std::string filename) override;
+ void flush_block() override;
+ std::string train(size_t buf_size);
+
+private:
+ const size_t blocks_to_keep, block_size;
+ std::string current_block;
+ uint64_t block_num = 0;
+ size_t num_files_in_block = 0;
+
+ std::mt19937 reservoir_rand{ 1234 }; // Fixed seed for reproducibility.
+ bool keep_current_block = true;
+ int64_t slot_for_current_block = -1;
+
+ std::vector<std::string> sampled_blocks;
+ std::vector<size_t> lengths;
+};
+
+class Corpus : public DatabaseReceiver {
+public:
+ Corpus(FILE *outfp, size_t block_size, ZSTD_CDict *cdict);
+ ~Corpus();
+
+ void add_file(std::string filename) override;
+ void flush_block() override;
+ void finish() override;
+
+ std::vector<uint64_t> filename_blocks;
+ size_t num_files = 0, num_files_in_block = 0, num_blocks = 0;
+ bool seen_trigram(uint32_t trgm)
+ {
+ return invindex[trgm] != nullptr;
+ }
+ PostingListBuilder &get_pl_builder(uint32_t trgm);
+ size_t num_trigrams() const;
+
+private:
+ std::unique_ptr<PostingListBuilder *[]> invindex;
+ FILE *outfp;
+ std::string current_block;
+ std::string tempbuf;
+ const size_t block_size;
+ ZSTD_CDict *cdict;
+ std::string directory_data;
+};
+
+class DatabaseBuilder {
+public:
+ DatabaseBuilder(const char *outfile, int block_size, std::string dictionary);
+ Corpus *start_corpus();
+ void finish_corpus();
+
+private:
+ FILE *outfp;
+ Header hdr;
+ const int block_size;
+ std::chrono::steady_clock::time_point corpus_start;
+ Corpus *corpus = nullptr;
+ ZSTD_CDict *cdict = nullptr;
+};
+
+#endif // !defined(_DATABASE_BUILDER_H)
dependencies: [uringdep, zstddep, threaddep, atomicdep],
install: true,
install_mode: ['rwxr-sr-x', 'root', 'mlocate'])
-executable('plocate-build', 'plocate-build.cpp',
+executable('plocate-build', ['plocate-build.cpp', 'database-builder.cpp'],
dependencies: [zstddep],
install: true,
install_dir: get_option('sbindir'))
+#include "database-builder.h"
#include "db.h"
#include "dprintf.h"
-#include "turbopfor-encode.h"
#include <algorithm>
-#include <assert.h>
#include <arpa/inet.h>
+#include <assert.h>
#include <chrono>
#include <getopt.h>
#include <iosfwd>
#include <stdlib.h>
#include <string.h>
#include <string>
-#include <string_view>
#include <sys/stat.h>
#include <utility>
#include <vector>
-#include <zdict.h>
-#include <zstd.h>
-
-#define P4NENC_BOUND(n) ((n + 127) / 128 + (n + 32) * sizeof(uint32_t))
-
-#define NUM_TRIGRAMS 16777216
using namespace std;
using namespace std::chrono;
-string zstd_compress(const string &src, ZSTD_CDict *cdict, string *tempbuf);
-
-constexpr unsigned num_overflow_slots = 16;
bool use_debug = false;
-static inline uint32_t read_unigram(const string_view s, size_t idx)
-{
- if (idx < s.size()) {
- return (unsigned char)s[idx];
- } else {
- return 0;
- }
-}
-
-static inline uint32_t read_trigram(const string_view s, size_t start)
-{
- return read_unigram(s, start) |
- (read_unigram(s, start + 1) << 8) |
- (read_unigram(s, start + 2) << 16);
-}
-
enum {
DBE_NORMAL = 0, /* A non-directory file */
DBE_DIRECTORY = 1, /* A directory */
uint8_t pad[4];
};
-class PostingListBuilder {
-public:
- inline void add_docid(uint32_t docid);
- void finish();
-
- string encoded;
- size_t num_docids = 0;
-
-private:
- void write_header(uint32_t docid);
- void append_block();
-
- vector<uint32_t> pending_deltas;
-
- uint32_t last_block_end, last_docid = -1;
-};
-
-void PostingListBuilder::add_docid(uint32_t docid)
-{
- // Deduplicate against the last inserted value, if any.
- if (docid == last_docid) {
- return;
- }
-
- if (num_docids == 0) {
- // Very first docid.
- write_header(docid);
- ++num_docids;
- last_block_end = last_docid = docid;
- return;
- }
-
- pending_deltas.push_back(docid - last_docid - 1);
- last_docid = docid;
- if (pending_deltas.size() == 128) {
- append_block();
- pending_deltas.clear();
- last_block_end = docid;
- }
- ++num_docids;
-}
-
-void PostingListBuilder::finish()
-{
- if (pending_deltas.empty()) {
- return;
- }
-
- assert(!encoded.empty()); // write_header() should already have run.
-
- // No interleaving for partial blocks.
- unsigned char buf[P4NENC_BOUND(128)];
- unsigned char *end = encode_pfor_single_block<128>(pending_deltas.data(), pending_deltas.size(), /*interleaved=*/false, buf);
- encoded.append(reinterpret_cast<char *>(buf), reinterpret_cast<char *>(end));
-}
-
-void PostingListBuilder::append_block()
-{
- unsigned char buf[P4NENC_BOUND(128)];
- assert(pending_deltas.size() == 128);
- unsigned char *end = encode_pfor_single_block<128>(pending_deltas.data(), 128, /*interleaved=*/true, buf);
- encoded.append(reinterpret_cast<char *>(buf), reinterpret_cast<char *>(end));
-}
-
-void PostingListBuilder::write_header(uint32_t docid)
-{
- unsigned char buf[P4NENC_BOUND(1)];
- unsigned char *end = write_baseval(docid, buf);
- encoded.append(reinterpret_cast<char *>(buf), end - buf);
-}
-
-class DatabaseReceiver {
-public:
- virtual ~DatabaseReceiver() = default;
- virtual void add_file(string filename) = 0;
- virtual void flush_block() = 0;
-};
-
-class DictionaryBuilder : public DatabaseReceiver {
-public:
- DictionaryBuilder(size_t blocks_to_keep, size_t block_size)
- : blocks_to_keep(blocks_to_keep), block_size(block_size) {}
- void add_file(string filename) override;
- void flush_block() override;
- string train(size_t buf_size);
-
-private:
- const size_t blocks_to_keep, block_size;
- string current_block;
- uint64_t block_num = 0;
- size_t num_files_in_block = 0;
-
- std::mt19937 reservoir_rand{ 1234 }; // Fixed seed for reproducibility.
- bool keep_current_block = true;
- int64_t slot_for_current_block = -1;
-
- vector<string> sampled_blocks;
- vector<size_t> lengths;
-};
-
-void DictionaryBuilder::add_file(string filename)
-{
- if (keep_current_block) { // Only bother saving the filenames if we're actually keeping the block.
- if (!current_block.empty()) {
- current_block.push_back('\0');
- }
- current_block += filename;
- }
- if (++num_files_in_block == block_size) {
- flush_block();
- }
-}
-
-void DictionaryBuilder::flush_block()
-{
- if (keep_current_block) {
- if (slot_for_current_block == -1) {
- lengths.push_back(current_block.size());
- sampled_blocks.push_back(move(current_block));
- } else {
- lengths[slot_for_current_block] = current_block.size();
- sampled_blocks[slot_for_current_block] = move(current_block);
- }
- }
- current_block.clear();
- num_files_in_block = 0;
- ++block_num;
-
- if (block_num < blocks_to_keep) {
- keep_current_block = true;
- slot_for_current_block = -1;
- } else {
- // Keep every block with equal probability (reservoir sampling).
- uint64_t idx = uniform_int_distribution<uint64_t>(0, block_num)(reservoir_rand);
- keep_current_block = (idx < blocks_to_keep);
- slot_for_current_block = idx;
- }
-}
-
-string DictionaryBuilder::train(size_t buf_size)
-{
- string dictionary_buf;
- sort(sampled_blocks.begin(), sampled_blocks.end()); // Seemingly important for decompression speed.
- for (const string &block : sampled_blocks) {
- dictionary_buf += block;
- }
-
- string buf;
- buf.resize(buf_size);
- size_t ret = ZDICT_trainFromBuffer(&buf[0], buf_size, dictionary_buf.data(), lengths.data(), lengths.size());
- if (ret == size_t(-1)) {
- return "";
- }
- dprintf("Sampled %zu bytes in %zu blocks, built a dictionary of size %zu\n", dictionary_buf.size(), lengths.size(), ret);
- buf.resize(ret);
-
- sampled_blocks.clear();
- lengths.clear();
-
- return buf;
-}
-
-class Corpus : public DatabaseReceiver {
-public:
- Corpus(FILE *outfp, size_t block_size, ZSTD_CDict *cdict)
- : invindex(new PostingListBuilder *[NUM_TRIGRAMS]), outfp(outfp), block_size(block_size), cdict(cdict)
- {
- fill(invindex.get(), invindex.get() + NUM_TRIGRAMS, nullptr);
- }
- ~Corpus() override
- {
- for (unsigned i = 0; i < NUM_TRIGRAMS; ++i) {
- delete invindex[i];
- }
- }
-
- void add_file(string filename) override;
- void flush_block() override;
-
- vector<uint64_t> filename_blocks;
- size_t num_files = 0, num_files_in_block = 0, num_blocks = 0;
- bool seen_trigram(uint32_t trgm)
- {
- return invindex[trgm] != nullptr;
- }
- PostingListBuilder &get_pl_builder(uint32_t trgm)
- {
- if (invindex[trgm] == nullptr) {
- invindex[trgm] = new PostingListBuilder;
- }
- return *invindex[trgm];
- }
- size_t num_trigrams() const;
-
-private:
- unique_ptr<PostingListBuilder *[]> invindex;
- FILE *outfp;
- string current_block;
- string tempbuf;
- const size_t block_size;
- ZSTD_CDict *cdict;
-};
-
-void Corpus::add_file(string filename)
-{
- ++num_files;
- if (!current_block.empty()) {
- current_block.push_back('\0');
- }
- current_block += filename;
- if (++num_files_in_block == block_size) {
- flush_block();
- }
-}
-
-void Corpus::flush_block()
-{
- if (current_block.empty()) {
- return;
- }
-
- uint32_t docid = num_blocks;
-
- // Create trigrams.
- const char *ptr = current_block.c_str();
- while (ptr < current_block.c_str() + current_block.size()) {
- string_view s(ptr);
- if (s.size() >= 3) {
- for (size_t j = 0; j < s.size() - 2; ++j) {
- uint32_t trgm = read_trigram(s, j);
- get_pl_builder(trgm).add_docid(docid);
- }
- }
- ptr += s.size() + 1;
- }
-
- // Compress and add the filename block.
- filename_blocks.push_back(ftell(outfp));
- string compressed = zstd_compress(current_block, cdict, &tempbuf);
- if (fwrite(compressed.data(), compressed.size(), 1, outfp) != 1) {
- perror("fwrite()");
- exit(1);
- }
-
- current_block.clear();
- num_files_in_block = 0;
- ++num_blocks;
-}
-
-size_t Corpus::num_trigrams() const
-{
- size_t num = 0;
- for (unsigned trgm = 0; trgm < NUM_TRIGRAMS; ++trgm) {
- if (invindex[trgm] != nullptr) {
- ++num;
- }
- }
- return num;
-}
-
string read_cstr(FILE *fp)
{
string ret;
}
}
-string zstd_compress(const string &src, ZSTD_CDict *cdict, string *tempbuf)
-{
- static ZSTD_CCtx *ctx = nullptr;
- if (ctx == nullptr) {
- ctx = ZSTD_createCCtx();
- }
-
- size_t max_size = ZSTD_compressBound(src.size());
- if (tempbuf->size() < max_size) {
- tempbuf->resize(max_size);
- }
- size_t size;
- if (cdict == nullptr) {
- size = ZSTD_compressCCtx(ctx, &(*tempbuf)[0], max_size, src.data(), src.size(), /*level=*/6);
- } else {
- size = ZSTD_compress_usingCDict(ctx, &(*tempbuf)[0], max_size, src.data(), src.size(), cdict);
- }
- return string(tempbuf->data(), size);
-}
-
-bool is_prime(uint32_t x)
-{
- if ((x % 2) == 0 || (x % 3) == 0) {
- return false;
- }
- uint32_t limit = ceil(sqrt(x));
- for (uint32_t factor = 5; factor <= limit; ++factor) {
- if ((x % factor) == 0) {
- return false;
- }
- }
- return true;
-}
-
-uint32_t next_prime(uint32_t x)
-{
- if ((x % 2) == 0) {
- ++x;
- }
- while (!is_prime(x)) {
- x += 2;
- }
- return x;
-}
-
-unique_ptr<Trigram[]> create_hashtable(Corpus &corpus, const vector<uint32_t> &all_trigrams, uint32_t ht_size, uint32_t num_overflow_slots)
-{
- unique_ptr<Trigram[]> ht(new Trigram[ht_size + num_overflow_slots + 1]); // 1 for the sentinel element at the end.
- for (unsigned i = 0; i < ht_size + num_overflow_slots + 1; ++i) {
- ht[i].trgm = uint32_t(-1);
- ht[i].num_docids = 0;
- ht[i].offset = 0;
- }
- for (uint32_t trgm : all_trigrams) {
- // We don't know offset yet, so set it to zero.
- Trigram to_insert{ trgm, uint32_t(corpus.get_pl_builder(trgm).num_docids), 0 };
-
- uint32_t bucket = hash_trigram(trgm, ht_size);
- unsigned distance = 0;
- while (ht[bucket].num_docids != 0) {
- // Robin Hood hashing; reduces the longest distance by a lot.
- unsigned other_distance = bucket - hash_trigram(ht[bucket].trgm, ht_size);
- if (distance > other_distance) {
- swap(to_insert, ht[bucket]);
- distance = other_distance;
- }
-
- ++bucket, ++distance;
- if (distance > num_overflow_slots) {
- return nullptr;
- }
- }
- ht[bucket] = to_insert;
- }
- return ht;
-}
-
-class DatabaseBuilder {
-public:
- DatabaseBuilder(const char *outfile, int block_size, string dictionary);
- Corpus *start_corpus();
- void finish_corpus();
-
-private:
- FILE *outfp;
- Header hdr;
- const int block_size;
- steady_clock::time_point corpus_start;
- Corpus *corpus = nullptr;
- ZSTD_CDict *cdict = nullptr;
-};
-
-DatabaseBuilder::DatabaseBuilder(const char *outfile, int block_size, string dictionary)
- : block_size(block_size)
-{
- umask(0027);
- outfp = fopen(outfile, "wb");
- if (outfp == nullptr) {
- perror(outfile);
- exit(1);
- }
-
- // Write the header.
- memcpy(hdr.magic, "\0plocate", 8);
- hdr.version = -1; // Mark as broken.
- hdr.hashtable_size = 0; // Not known yet.
- hdr.extra_ht_slots = num_overflow_slots;
- hdr.num_docids = 0;
- hdr.hash_table_offset_bytes = -1; // We don't know these offsets yet.
- hdr.max_version = 1;
- hdr.filename_index_offset_bytes = -1;
- hdr.zstd_dictionary_length_bytes = -1;
- fwrite(&hdr, sizeof(hdr), 1, outfp);
-
- if (dictionary.empty()) {
- hdr.zstd_dictionary_offset_bytes = 0;
- hdr.zstd_dictionary_length_bytes = 0;
- } else {
- hdr.zstd_dictionary_offset_bytes = ftell(outfp);
- fwrite(dictionary.data(), dictionary.size(), 1, outfp);
- hdr.zstd_dictionary_length_bytes = dictionary.size();
- cdict = ZSTD_createCDict(dictionary.data(), dictionary.size(), /*level=*/6);
- }
-}
-
-Corpus *DatabaseBuilder::start_corpus()
-{
- corpus_start = steady_clock::now();
- corpus = new Corpus(outfp, block_size, cdict);
- return corpus;
-}
-
-void DatabaseBuilder::finish_corpus()
-{
- corpus->flush_block();
- hdr.num_docids = corpus->filename_blocks.size();
-
- // Stick an empty block at the end as sentinel.
- corpus->filename_blocks.push_back(ftell(outfp));
- const size_t bytes_for_filenames = corpus->filename_blocks.back() - corpus->filename_blocks.front();
-
- // Write the offsets to the filenames.
- hdr.filename_index_offset_bytes = ftell(outfp);
- const size_t bytes_for_filename_index = corpus->filename_blocks.size() * sizeof(uint64_t);
- fwrite(corpus->filename_blocks.data(), corpus->filename_blocks.size(), sizeof(uint64_t), outfp);
- corpus->filename_blocks.clear();
- corpus->filename_blocks.shrink_to_fit();
-
- // Finish up encoding the posting lists.
- size_t trigrams = 0, longest_posting_list = 0;
- size_t bytes_for_posting_lists = 0;
- for (unsigned trgm = 0; trgm < NUM_TRIGRAMS; ++trgm) {
- if (!corpus->seen_trigram(trgm))
- continue;
- PostingListBuilder &pl_builder = corpus->get_pl_builder(trgm);
- pl_builder.finish();
- longest_posting_list = max(longest_posting_list, pl_builder.num_docids);
- trigrams += pl_builder.num_docids;
- bytes_for_posting_lists += pl_builder.encoded.size();
- }
- size_t num_trigrams = corpus->num_trigrams();
- dprintf("%zu files, %zu different trigrams, %zu entries, avg len %.2f, longest %zu\n",
- corpus->num_files, num_trigrams, trigrams, double(trigrams) / num_trigrams, longest_posting_list);
- dprintf("%zu bytes used for posting lists (%.2f bits/entry)\n", bytes_for_posting_lists, 8 * bytes_for_posting_lists / double(trigrams));
-
- dprintf("Building posting lists took %.1f ms.\n\n", 1e3 * duration<float>(steady_clock::now() - corpus_start).count());
-
- // Find the used trigrams.
- vector<uint32_t> all_trigrams;
- for (unsigned trgm = 0; trgm < NUM_TRIGRAMS; ++trgm) {
- if (corpus->seen_trigram(trgm)) {
- all_trigrams.push_back(trgm);
- }
- }
-
- // Create the hash table.
- unique_ptr<Trigram[]> hashtable;
- uint32_t ht_size = next_prime(all_trigrams.size());
- for (;;) {
- hashtable = create_hashtable(*corpus, all_trigrams, ht_size, num_overflow_slots);
- if (hashtable == nullptr) {
- dprintf("Failed creating hash table of size %u, increasing by 5%% and trying again.\n", ht_size);
- ht_size = next_prime(ht_size * 1.05);
- } else {
- dprintf("Created hash table of size %u.\n\n", ht_size);
- break;
- }
- }
-
- // Find the offsets for each posting list.
- size_t bytes_for_hashtable = (ht_size + num_overflow_slots + 1) * sizeof(Trigram);
- uint64_t offset = ftell(outfp) + bytes_for_hashtable;
- for (unsigned i = 0; i < ht_size + num_overflow_slots + 1; ++i) {
- hashtable[i].offset = offset; // Needs to be there even for empty slots.
- if (hashtable[i].num_docids == 0) {
- continue;
- }
-
- const string &encoded = corpus->get_pl_builder(hashtable[i].trgm).encoded;
- offset += encoded.size();
- }
-
- // Write the hash table.
- hdr.hash_table_offset_bytes = ftell(outfp);
- hdr.hashtable_size = ht_size;
- fwrite(hashtable.get(), ht_size + num_overflow_slots + 1, sizeof(Trigram), outfp);
-
- // Write the actual posting lists.
- for (unsigned i = 0; i < ht_size + num_overflow_slots + 1; ++i) {
- if (hashtable[i].num_docids == 0) {
- continue;
- }
- const string &encoded = corpus->get_pl_builder(hashtable[i].trgm).encoded;
- fwrite(encoded.data(), encoded.size(), 1, outfp);
- }
-
- // Rewind, and write the updated header.
- hdr.version = 1;
- fseek(outfp, 0, SEEK_SET);
- fwrite(&hdr, sizeof(hdr), 1, outfp);
- fclose(outfp);
-
- size_t total_bytes = (bytes_for_hashtable + bytes_for_posting_lists + bytes_for_filename_index + bytes_for_filenames);
-
- dprintf("Block size: %7d files\n", block_size);
- dprintf("Dictionary: %'7.1f MB\n", hdr.zstd_dictionary_length_bytes / 1048576.0);
- dprintf("Hash table: %'7.1f MB\n", bytes_for_hashtable / 1048576.0);
- dprintf("Posting lists: %'7.1f MB\n", bytes_for_posting_lists / 1048576.0);
- dprintf("Filename index: %'7.1f MB\n", bytes_for_filename_index / 1048576.0);
- dprintf("Filenames: %'7.1f MB\n", bytes_for_filenames / 1048576.0);
- dprintf("Total: %'7.1f MB\n", total_bytes / 1048576.0);
- dprintf("\n");
-}
-
void do_build(const char *infile, const char *outfile, int block_size, bool plaintext)
{
FILE *infp = fopen(infile, "rb");
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