ldb: support --fix_prefix_len

Summary:
ldb to support --fix_prefix_len to allow us to verify more cases.
Also fix a small issue that --bloom_bits might not be applied if --block_size is not given.

Test Plan: run ldb tool against an example DB.

Reviewers: ljin, yhchiang, rven, igor

Reviewed By: igor

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D24819

util/ldb_cmd.cc

@@ -40,6 +40,7 @@ const string LDBCommand::ARG_FROM = "from";
 const string LDBCommand::ARG_TO = "to";
 const string LDBCommand::ARG_MAX_KEYS = "max_keys";
 const string LDBCommand::ARG_BLOOM_BITS = "bloom_bits";
+const string LDBCommand::ARG_FIX_PREFIX_LEN = "fix_prefix_len";
 const string LDBCommand::ARG_COMPRESSION_TYPE = "compression_type";
 const string LDBCommand::ARG_BLOCK_SIZE = "block_size";
 const string LDBCommand::ARG_AUTO_COMPACTION = "auto_compaction";
@@ -221,9 +222,11 @@ Options LDBCommand::PrepareOptionsForOpenDB() {
   map<string, string>::const_iterator itr;
 
   BlockBasedTableOptions table_options;
+  bool use_table_options = false;
   int bits;
   if (ParseIntOption(option_map_, ARG_BLOOM_BITS, bits, exec_state_)) {
     if (bits > 0) {
+      use_table_options = true;
       table_options.filter_policy.reset(NewBloomFilterPolicy(bits));
     } else {
       exec_state_ = LDBCommandExecuteResult::FAILED(ARG_BLOOM_BITS +
@@ -234,14 +237,18 @@ Options LDBCommand::PrepareOptionsForOpenDB() {
   int block_size;
   if (ParseIntOption(option_map_, ARG_BLOCK_SIZE, block_size, exec_state_)) {
     if (block_size > 0) {
+      use_table_options = true;
       table_options.block_size = block_size;
-      opt.table_factory.reset(NewBlockBasedTableFactory(table_options));
     } else {
       exec_state_ = LDBCommandExecuteResult::FAILED(ARG_BLOCK_SIZE +
                       " must be > 0.");
     }
   }
 
+  if (use_table_options) {
+    opt.table_factory.reset(NewBlockBasedTableFactory(table_options));
+  }
+
   itr = option_map_.find(ARG_AUTO_COMPACTION);
   if (itr != option_map_.end()) {
     opt.disable_auto_compactions = ! StringToBool(itr->second);
@@ -294,6 +301,18 @@ Options LDBCommand::PrepareOptionsForOpenDB() {
     opt.db_paths.emplace_back(db_path_, std::numeric_limits<uint64_t>::max());
   }
 
+  int fix_prefix_len;
+  if (ParseIntOption(option_map_, ARG_FIX_PREFIX_LEN, fix_prefix_len,
+                     exec_state_)) {
+    if (fix_prefix_len > 0) {
+      opt.prefix_extractor.reset(
+          NewFixedPrefixTransform(static_cast<size_t>(fix_prefix_len)));
+    } else {
+      exec_state_ =
+          LDBCommandExecuteResult::FAILED(ARG_FIX_PREFIX_LEN + " must be > 0.");
+    }
+  }
+
   return opt;
 }
 

util/ldb_cmd.h

@@ -46,6 +46,7 @@ public:
   static const string ARG_TO;
   static const string ARG_MAX_KEYS;
   static const string ARG_BLOOM_BITS;
+  static const string ARG_FIX_PREFIX_LEN;
   static const string ARG_COMPRESSION_TYPE;
   static const string ARG_BLOCK_SIZE;
   static const string ARG_AUTO_COMPACTION;
@@ -284,9 +285,10 @@ protected:
    * passed in.
    */
   vector<string> BuildCmdLineOptions(vector<string> options) {
-    vector<string> ret = {ARG_DB, ARG_BLOOM_BITS, ARG_BLOCK_SIZE,
-                          ARG_AUTO_COMPACTION, ARG_COMPRESSION_TYPE,
-                          ARG_WRITE_BUFFER_SIZE, ARG_FILE_SIZE};
+    vector<string> ret = {ARG_DB,               ARG_BLOOM_BITS,
+                          ARG_BLOCK_SIZE,       ARG_AUTO_COMPACTION,
+                          ARG_COMPRESSION_TYPE, ARG_WRITE_BUFFER_SIZE,
+                          ARG_FILE_SIZE,        ARG_FIX_PREFIX_LEN};
     ret.insert(ret.end(), options.begin(), options.end());
     return ret;
   }

util/ldb_tool.cc

@@ -47,6 +47,7 @@ public:
         " with 'put','get','scan','dump','query','batchput'"
         " : DB supports ttl and value is internally timestamp-suffixed\n");
     ret.append("  --" + LDBCommand::ARG_BLOOM_BITS + "=<int,e.g.:14>\n");
+    ret.append("  --" + LDBCommand::ARG_FIX_PREFIX_LEN + "=<int,e.g.:14>\n");
     ret.append("  --" + LDBCommand::ARG_COMPRESSION_TYPE +
         "=<no|snappy|zlib|bzip2>\n");
     ret.append("  --" + LDBCommand::ARG_BLOCK_SIZE +