xxHash

Summary:
Originally: https://github.com/facebook/rocksdb/pull/87/files

I'm taking over to apply some finishing touches

Test Plan: will add tests

Reviewers: dhruba, haobo, sdong, yhchiang, ljin

Reviewed By: yhchiang

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18315

HISTORY.md

@@ -4,12 +4,11 @@
 
 ### Public API changes
 * Added _LEVEL to all InfoLogLevel enums
+* Deprecated ReadOptions.prefix and ReadOptions.prefix_seek. Seek() defaults to prefix-based seek when Options.prefix_extractor is supplied. More detail is documented in https://github.com/facebook/rocksdb/wiki/Prefix-Seek-API-Changes
 
 ### New Features
 * Column family support
-
-### Public API changes
-* Deprecated ReadOptions.prefix and ReadOptions.prefix_seek. Seek() defaults to prefix-based seek when Options.prefix_extractor is supplied. More detail is documented in https://github.com/facebook/rocksdb/wiki/Prefix-Seek-API-Changes
+* Added an option to use different checksum functions in BlockBasedTableOptions
 
 ## 2.8.0 (04/04/2014)
 

db/db_bench.cc

@@ -36,6 +36,7 @@
 #include "util/string_util.h"
 #include "util/statistics.h"
 #include "util/testutil.h"
+#include "util/xxhash.h"
 #include "hdfs/env_hdfs.h"
 #include "utilities/merge_operators.h"
 
@@ -64,6 +65,7 @@ DEFINE_string(benchmarks,
               "randomwithverify,"
               "fill100K,"
               "crc32c,"
+              "xxhash,"
               "compress,"
               "uncompress,"
               "acquireload,",
@@ -107,6 +109,7 @@ DEFINE_string(benchmarks,
               "\tseekrandom    -- N random seeks\n"
               "\tseekrandom    -- 1 writer, N threads doing random seeks\n"
               "\tcrc32c        -- repeated crc32c of 4K of data\n"
+              "\txxhash        -- repeated xxHash of 4K of data\n"
               "\tacquireload   -- load N*1000 times\n"
               "Meta operations:\n"
               "\tcompact     -- Compact the entire DB\n"
@@ -1234,6 +1237,8 @@ class Benchmark {
         method = &Benchmark::Compact;
       } else if (name == Slice("crc32c")) {
         method = &Benchmark::Crc32c;
+      } else if (name == Slice("xxhash")) {
+        method = &Benchmark::xxHash;
       } else if (name == Slice("acquireload")) {
         method = &Benchmark::AcquireLoad;
       } else if (name == Slice("compress")) {
@@ -1382,6 +1387,25 @@ class Benchmark {
     thread->stats.AddMessage(label);
   }
 
+  void xxHash(ThreadState* thread) {
+    // Checksum about 500MB of data total
+    const int size = 4096;
+    const char* label = "(4K per op)";
+    std::string data(size, 'x');
+    int64_t bytes = 0;
+    unsigned int xxh32 = 0;
+    while (bytes < 500 * 1048576) {
+      xxh32 = XXH32(data.data(), size, 0);
+      thread->stats.FinishedSingleOp(nullptr);
+      bytes += size;
+    }
+    // Print so result is not dead
+    fprintf(stderr, "... xxh32=0x%x\r", static_cast<unsigned int>(xxh32));
+
+    thread->stats.AddBytes(bytes);
+    thread->stats.AddMessage(label);
+  }
+
   void AcquireLoad(ThreadState* thread) {
     int dummy;
     port::AtomicPointer ap(&dummy);

db/db_test.cc

@@ -316,6 +316,7 @@ class DBTest {
     kUniversalCompaction,
     kCompressedBlockCache,
     kInfiniteMaxOpenFiles,
+    kxxHashChecksum,
     kEnd
   };
   int option_config_;
@@ -496,6 +497,12 @@ class DBTest {
       case kInfiniteMaxOpenFiles:
         options.max_open_files = -1;
         break;
+      case kxxHashChecksum: {
+        BlockBasedTableOptions table_options;
+        table_options.checksum = kxxHash;
+        options.table_factory.reset(NewBlockBasedTableFactory(table_options));
+        break;
+      }
       case kBlockBasedTableWithPrefixHashIndex: {
         BlockBasedTableOptions table_options;
         table_options.index_type = BlockBasedTableOptions::kHashSearch;
@@ -6778,7 +6785,40 @@ TEST(DBTest, TailingIteratorPrefixSeek) {
   ASSERT_TRUE(!iter->Valid());
 }
 
+TEST(DBTest, ChecksumTest) {
+  BlockBasedTableOptions table_options;
+  Options options = CurrentOptions();
+
+  table_options.checksum = kCRC32c;
+  options.table_factory.reset(NewBlockBasedTableFactory(table_options));
+  Reopen(&options);
+  ASSERT_OK(Put("a", "b"));
+  ASSERT_OK(Put("c", "d"));
+  ASSERT_OK(Flush());  // table with crc checksum
+
+  table_options.checksum = kxxHash;
+  options.table_factory.reset(NewBlockBasedTableFactory(table_options));
+  Reopen(&options);
+  ASSERT_OK(Put("e", "f"));
+  ASSERT_OK(Put("g", "h"));
+  ASSERT_OK(Flush());  // table with xxhash checksum
+
+  table_options.checksum = kCRC32c;
+  options.table_factory.reset(NewBlockBasedTableFactory(table_options));
+  Reopen(&options);
+  ASSERT_EQ("b", Get("a"));
+  ASSERT_EQ("d", Get("c"));
+  ASSERT_EQ("f", Get("e"));
+  ASSERT_EQ("h", Get("g"));
 
+  table_options.checksum = kCRC32c;
+  options.table_factory.reset(NewBlockBasedTableFactory(table_options));
+  Reopen(&options);
+  ASSERT_EQ("b", Get("a"));
+  ASSERT_EQ("d", Get("c"));
+  ASSERT_EQ("f", Get("e"));
+  ASSERT_EQ("h", Get("g"));
+}
 }  // namespace rocksdb
 
 int main(int argc, char** argv) {

include/rocksdb/table.h

@@ -38,6 +38,12 @@ struct Options;
 
 using std::unique_ptr;
 
+enum ChecksumType : char {
+  kNoChecksum = 0x0,  // not yet supported. Will fail
+  kCRC32c = 0x1,
+  kxxHash = 0x2,
+};
+
 // For advanced user only
 struct BlockBasedTableOptions {
   // @flush_block_policy_factory creates the instances of flush block policy.
@@ -67,6 +73,11 @@ struct BlockBasedTableOptions {
   };
 
   IndexType index_type = kBinarySearch;
+
+  // Use the specified checksum type. Newly created table files will be
+  // protected with this checksum type. Old table files will still be readable,
+  // even though they have different checksum type.
+  ChecksumType checksum = kCRC32c;
 };
 
 // Table Properties that are specific to block-based table properties.

table/block_based_table_builder.cc

@@ -37,6 +37,7 @@
 #include "util/coding.h"
 #include "util/crc32c.h"
 #include "util/stop_watch.h"
+#include "util/xxhash.h"
 
 namespace rocksdb {
 
@@ -231,12 +232,14 @@ Slice CompressBlock(const Slice& raw,
 }  // anonymous namespace
 
 // kBlockBasedTableMagicNumber was picked by running
-//    echo http://code.google.com/p/leveldb/ | sha1sum
+//    echo rocksdb.table.block_based | sha1sum
 // and taking the leading 64 bits.
 // Please note that kBlockBasedTableMagicNumber may also be accessed by
 // other .cc files so it have to be explicitly declared with "extern".
-extern const uint64_t kBlockBasedTableMagicNumber
-    = 0xdb4775248b80fb57ull;
+extern const uint64_t kBlockBasedTableMagicNumber = 0x88e241b785f4cff7ull;
+// We also support reading and writing legacy block based table format (for
+// backwards compatibility)
+extern const uint64_t kLegacyBlockBasedTableMagicNumber = 0xdb4775248b80fb57ull;
 
 // A collector that collects properties of interest to block-based table.
 // For now this class looks heavy-weight since we only write one additional
@@ -289,6 +292,7 @@ struct BlockBasedTableBuilder::Rep {
 
   std::string last_key;
   CompressionType compression_type;
+  ChecksumType checksum_type;
   TableProperties props;
 
   bool closed = false;  // Either Finish() or Abandon() has been called.
@@ -303,14 +307,16 @@ struct BlockBasedTableBuilder::Rep {
 
   Rep(const Options& opt, const InternalKeyComparator& icomparator,
       WritableFile* f, FlushBlockPolicyFactory* flush_block_policy_factory,
-      CompressionType compression_type, IndexType index_block_type)
+      CompressionType compression_type, IndexType index_block_type,
+      ChecksumType checksum_type)
       : options(opt),
         internal_comparator(icomparator),
         file(f),
         data_block(options, &internal_comparator),
         index_builder(
             CreateIndexBuilder(index_block_type, &internal_comparator)),
         compression_type(compression_type),
+        checksum_type(checksum_type),
         filter_block(opt.filter_policy == nullptr
                          ? nullptr
                          : new FilterBlockBuilder(opt, &internal_comparator)),
@@ -330,7 +336,8 @@ BlockBasedTableBuilder::BlockBasedTableBuilder(
     : rep_(new Rep(options, internal_comparator, file,
                    table_options.flush_block_policy_factory.get(),
                    compression_type,
-                   BlockBasedTableOptions::IndexType::kBinarySearch)) {
+                   BlockBasedTableOptions::IndexType::kBinarySearch,
+                   table_options.checksum)) {
   if (rep_->filter_block != nullptr) {
     rep_->filter_block->StartBlock(0);
   }
@@ -443,9 +450,27 @@ void BlockBasedTableBuilder::WriteRawBlock(const Slice& 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));
+    char* trailer_without_type = trailer + 1;
+    switch (r->checksum_type) {
+      case kNoChecksum:
+        // we don't support no checksum yet
+        assert(false);
+        // intentional fallthrough in release binary
+      case kCRC32c: {
+        auto crc = crc32c::Value(block_contents.data(), block_contents.size());
+        crc = crc32c::Extend(crc, trailer, 1);  // Extend to cover block type
+        EncodeFixed32(trailer_without_type, crc32c::Mask(crc));
+        break;
+      }
+      case kxxHash: {
+        void* xxh = XXH32_init(0);
+        XXH32_update(xxh, block_contents.data(), block_contents.size());
+        XXH32_update(xxh, trailer, 1);  // Extend  to cover block type
+        EncodeFixed32(trailer_without_type, XXH32_digest(xxh));
+        break;
+      }
+    }
+
     r->status = r->file->Append(Slice(trailer, kBlockTrailerSize));
     if (r->status.ok()) {
       r->status = InsertBlockInCache(block_contents, type, handle);
@@ -596,9 +621,19 @@ Status BlockBasedTableBuilder::Finish() {
 
   // Write footer
   if (ok()) {
-    Footer footer(kBlockBasedTableMagicNumber);
+    // No need to write out new footer if we're using default checksum.
+    // We're writing legacy magic number because we want old versions of RocksDB
+    // be able to read files generated with new release (just in case if
+    // somebody wants to roll back after an upgrade)
+    // TODO(icanadi) at some point in the future, when we're absolutely sure
+    // nobody will roll back to RocksDB 2.x versions, retire the legacy magic
+    // number and always write new table files with new magic number
+    bool legacy = (r->checksum_type == kCRC32c);
+    Footer footer(legacy ? kLegacyBlockBasedTableMagicNumber
+                         : kBlockBasedTableMagicNumber);
     footer.set_metaindex_handle(metaindex_block_handle);
     footer.set_index_handle(index_block_handle);
+    footer.set_checksum(r->checksum_type);
     std::string footer_encoding;
     footer.EncodeTo(&footer_encoding);
     r->status = r->file->Append(footer_encoding);