RocksDBLite

Summary:
Introducing RocksDBLite! Removes all the non-essential features and reduces the binary size. This effort should help our adoption on mobile.

Binary size when compiling for IOS (`TARGET_OS=IOS m static_lib`) is down to 9MB from 15MB (without stripping)

Test Plan: compiles :)

Reviewers: dhruba, haobo, ljin, sdong, yhchiang

Reviewed By: yhchiang

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17835

Author: igorcanadi

Makefile

@@ -15,7 +15,12 @@ endif
 
 ifeq ($(MAKECMDGOALS),shared_lib)
 PLATFORM_SHARED_LDFLAGS=-fPIC
+OPT += -DNDEBUG
+endif
+ifeq ($(MAKECMDGOALS),static_lib)
+OPT += -DNDEBUG
 endif
+
 #-----------------------------------------------
 
 # detect what platform we're building on

ROCKSDB_LITE.md

@@ -0,0 +1,20 @@
+# RocksDBLite
+
+RocksDBLite is a project focused on mobile use cases, which don't need a lot of fancy things we've built for server workloads and they are very sensitive to binary size. For that reason, we added a compile flag ROCKSDB_LITE that comments out a lot of the nonessential code and keeps the binary lean.
+
+Some examples of the features disabled by ROCKSDB_LITE:
+* compiled-in support for LDB tool
+* No backupable DB
+* No support for replication (which we provide in form of TrasactionalIterator)
+* No advanced monitoring tools
+* No special-purpose memtables that are highly optimized for specific use cases
+
+When adding a new big feature to RocksDB, please add ROCKSDB_LITE compile guard if:
+* Nobody from mobile really needs your feature,
+* Your feature is adding a lot of weight to the binary.
+
+Don't add ROCKSDB_LITE compile guard if:
+* It would introduce a lot of code complexity. Compile guards make code harder to read. It's a trade-off.
+* Your feature is not adding a lot of weight.
+
+If unsure, ask. :)

build_tools/build_detect_platform

@@ -100,7 +100,7 @@ case "$TARGET_OS" in
         ;;
     IOS)
         PLATFORM=IOS
-        COMMON_FLAGS="$COMMON_FLAGS -DOS_MACOSX -DIOS_CROSS_COMPILE"
+        COMMON_FLAGS="$COMMON_FLAGS -DOS_MACOSX -DIOS_CROSS_COMPILE -DROCKSDB_LITE"
         PLATFORM_SHARED_EXT=dylib
         PLATFORM_SHARED_LDFLAGS="-dynamiclib -install_name "
         CROSS_COMPILE=true

db/c.cc

@@ -7,6 +7,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file. See the AUTHORS file for names of contributors.
 
+#ifndef ROCKSDB_LITE
+
 #include "rocksdb/c.h"
 
 #include <stdlib.h>
@@ -1467,3 +1469,5 @@ extern void rocksdb_livefiles_destroy(
 }
 
 }  // end extern "C"
+
+#endif  // ROCKSDB_LITE

db/db_filesnapshot.cc

@@ -7,6 +7,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#ifndef ROCKSDB_LITE
+
 #define __STDC_FORMAT_MACROS
 #include <inttypes.h>
 #include <algorithm>
@@ -166,3 +168,5 @@ Status DBImpl::GetSortedWalFiles(VectorLogPtr& files) {
 }
 
 }
+
+#endif  // ROCKSDB_LITE