Add db_dump tool to dump DB keys

Summary:
Create a tool to iterate through keys and dump values. Current options
as follows:

db_dump --start=[START_KEY] --end=[END_KEY] --max_keys=[NUM] --stats
[PATH]

START_KEY: First key to start at
END_KEY: Key to end at (not inclusive)
NUM: Maximum number of keys to dump
PATH: Path to leveldb DB

The --stats command line argument prints out the DB stats before dumping
the keys.

Test Plan:
- Tested with invalid args
- Tested with invalid path
- Used empty DB
- Used filled DB
- Tried various permutations of command line options

Reviewers: dhruba, heyongqiang

Reviewed By: dhruba

Differential Revision: https://reviews.facebook.net/D5643

Makefile

@@ -56,7 +56,8 @@ TESTS = \
 
 TOOLS = \
 	manifest_dump \
-        sst_dump
+        sst_dump \
+        ldb
 
 PROGRAMS = db_bench $(TESTS) $(TOOLS)
 BENCHMARKS = db_bench_sqlite3 db_bench_tree_db
@@ -199,6 +200,9 @@ filelock_test: util/filelock_test.o $(LIBOBJECTS) $(TESTHARNESS)
 sst_dump: tools/sst_dump.o $(LIBOBJECTS)
 	$(CXX) tools/sst_dump.o $(LIBOBJECTS) -o $@ $(LDFLAGS)
 
+ldb: tools/ldb.o $(LIBOBJECTS)
+	$(CXX) tools/ldb.o $(LIBOBJECTS) -o $@ $(LDFLAGS)
+
 # recreate the version file with the latest git revision
 $(VERSIONFILE):	build_detect_version
 	$(shell ./build_detect_platform build_config.mk)

tools/ldb.cc

@@ -0,0 +1,146 @@
+// Copyright (c) 2012 Facebook. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <string>
+#include <iostream>
+#include <sstream>
+
+#include "leveldb/db.h"
+#include "leveldb/iterator.h"
+
+std::string HexToString(std::string str) {
+  std::string parsed;
+  for (int i = 0; i < str.length(); ) {
+    int c;
+    sscanf(str.c_str() + i, "%2X", &c);
+    parsed.push_back(c);
+    i += 2;
+  }
+  return parsed;
+}
+
+static void print_help() {
+  fprintf(stderr,
+      "db_dump "
+      "--start=[START_KEY] "
+      "--end=[END_KEY] "
+      "--max_keys=[NUM] "
+      "--hex "
+      "--count_only "
+      "--stats "
+      "[PATH]\n");
+}
+
+int main(int argc, char** argv) {
+  std::string db_path;
+  std::string start;
+  std::string end;
+  uint64_t max_keys = -1;
+  bool print_stats = false;
+  bool count_only = false;
+  uint64_t count = 0;
+  bool hex = false;
+
+  // Parse command line args
+  char junk;
+  uint64_t n;
+  for (int i = 1; i < argc; i++) {
+    if (strncmp(argv[i], "--start=", 8) == 0) {
+      start= argv[i] + 8;
+    } else if (strncmp(argv[i], "--end=", 6) == 0) {
+      end = argv[i] + 6;
+    } else if (sscanf(argv[i], "--max_keys=%ld%c", &n, &junk) == 1) {
+      max_keys = n;
+    } else if (strncmp(argv[i], "--stats", 7) == 0) {
+      print_stats = true;
+    } else if (strncmp(argv[i], "--count_only", 12) == 0) {
+      count_only = true;
+    } else if (strncmp(argv[i], "--hex", 5) == 0) {
+      hex = true;
+    } else if (i == (argc - 1)) {
+      db_path = argv[i];
+    } else {
+      print_help();
+      exit(1);
+    }
+  }
+
+  if (hex) {
+    start = HexToString(start);
+    end = HexToString(end);
+  }
+
+  if (db_path.empty()) {
+    print_help();
+    exit(1);
+  }
+
+  // Open DB
+  leveldb::Options options;
+  leveldb::DB *db;
+  leveldb::Status status = leveldb::DB::Open(options, db_path, &db);
+
+  if (!status.ok()) {
+    fprintf(stderr, "%s\n", status.ToString().c_str());
+    exit(1);
+  }
+
+  // Print DB stats if desired
+  if (print_stats) {
+    std::string stats;
+    if (db->GetProperty("leveldb.stats", &stats)) {
+      fprintf(stdout, "%s\n", stats.c_str());
+    }
+  }
+
+  // Setup key iterator
+  leveldb::Iterator* iter = db->NewIterator(leveldb::ReadOptions());
+  status = iter->status();
+  if (!status.ok()) {
+    fprintf(stderr, "%s\n", status.ToString().c_str());
+    delete db;
+    exit(1);
+  }
+
+  for (iter->Seek(start); iter->Valid(); iter->Next()) {
+    // If end marker was specified, we stop before it
+    if (!end.empty() && (iter->key().ToString() >= end))
+      break;
+
+    // Terminate if maximum number of keys have been dumped
+    if (max_keys == 0)
+      break;
+
+    --max_keys;
+    ++count;
+
+    if (!count_only) {
+      if (hex) {
+        std::string str = iter->key().ToString();
+        for (int i = 0; i < str.length(); ++i) {
+          fprintf(stdout, "%X", str[i]);
+        }
+        fprintf(stdout, " ==> ");
+        str = iter->value().ToString();
+        for (int i = 0; i < str.length(); ++i) {
+          fprintf(stdout, "%X", str[i]);
+        }
+        fprintf(stdout, "\n");
+      } else {
+        fprintf(stdout, "%s ==> %s\n",
+            iter->key().ToString().c_str(),
+            iter->value().ToString().c_str());
+      }
+    }
+  }
+
+  fprintf(stdout, "Keys in range: %d\n", count);
+
+  // Clean up
+  delete iter;
+  delete db;
+
+  return 0;
+}
+