ldb option for compression dictionary size

Summary:
Expose the option so it's easy to run offline tests of compression
dictionary feature.

Test Plan:
verified compression dictionary is loaded into lz4 for below command:

  $ ./ldb compact --compression_type=lz4 --compression_max_dict_bytes=16384 --db=/tmp/feed-compression-test/

Reviewers: IslamAbdelRahman, sdong

Reviewed By: sdong

Subscribers: andrewkr, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D57441

include/rocksdb/utilities/ldb_cmd.h

@@ -44,6 +44,7 @@ class LDBCommand {
   static const std::string ARG_BLOOM_BITS;
   static const std::string ARG_FIX_PREFIX_LEN;
   static const std::string ARG_COMPRESSION_TYPE;
+  static const std::string ARG_COMPRESSION_MAX_DICT_BYTES;
   static const std::string ARG_BLOCK_SIZE;
   static const std::string ARG_AUTO_COMPACTION;
   static const std::string ARG_DB_WRITE_BUFFER_SIZE;

tools/ldb_cmd.cc

@@ -58,6 +58,8 @@ 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_COMPRESSION_MAX_DICT_BYTES =
+    "compression_max_dict_bytes";
 const string LDBCommand::ARG_BLOCK_SIZE = "block_size";
 const string LDBCommand::ARG_AUTO_COMPACTION = "auto_compaction";
 const string LDBCommand::ARG_DB_WRITE_BUFFER_SIZE = "db_write_buffer_size";
@@ -363,6 +365,7 @@ vector<string> LDBCommand::BuildCmdLineOptions(vector<string> options) {
                         ARG_BLOCK_SIZE,
                         ARG_AUTO_COMPACTION,
                         ARG_COMPRESSION_TYPE,
+                        ARG_COMPRESSION_MAX_DICT_BYTES,
                         ARG_WRITE_BUFFER_SIZE,
                         ARG_FILE_SIZE,
                         ARG_FIX_PREFIX_LEN,
@@ -483,6 +486,17 @@ Options LDBCommand::PrepareOptionsForOpenDB() {
     }
   }
 
+  int compression_max_dict_bytes;
+  if (ParseIntOption(option_map_, ARG_COMPRESSION_MAX_DICT_BYTES,
+                     compression_max_dict_bytes, exec_state_)) {
+    if (compression_max_dict_bytes >= 0) {
+      opt.compression_opts.max_dict_bytes = compression_max_dict_bytes;
+    } else {
+      exec_state_ = LDBCommandExecuteResult::Failed(
+          ARG_COMPRESSION_MAX_DICT_BYTES + " must be >= 0.");
+    }
+  }
+
   int db_write_buffer_size;
   if (ParseIntOption(option_map_, ARG_DB_WRITE_BUFFER_SIZE,
         db_write_buffer_size, exec_state_)) {

tools/ldb_tool.cc

@@ -45,7 +45,9 @@ public:
     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");
+        "=<no|snappy|zlib|bzip2|lz4|lz4hc|xpress|zstd>\n");
+    ret.append("  --" + LDBCommand::ARG_COMPRESSION_MAX_DICT_BYTES +
+        "=<int,e.g.:14>\n");
     ret.append("  --" + LDBCommand::ARG_BLOCK_SIZE +
         "=<block_size_in_bytes>\n");
     ret.append("  --" + LDBCommand::ARG_AUTO_COMPACTION + "=<true|false>\n");