sqlite3 rollback without any reasonable cause in my iOS app

first of all, I didn't use any transaction here, it's a simple insert or update operation with sqlite3. And the following is the log:

2015/01/27 12:50:52:935  void __sqlite_update_proc(void *, int, const char *, const char *, sqlite_int64) #359 [VERBOSE] __sqlite_update_hook operation=SQLITE_INSERT, db=main, table=WKChat_6145e5275c040be0fb1f72ea658632e3, rowId=2

2015/01/27 12:50:52:936  void __sqlite_rollback_proc(void *) #375 [VERBOSE] __sqlite_rollback_hook
2015/01/27 12:50:52:937  <L_DB> -[WKReceiveMessageHandler pushReceived:value:] #79 [INFO] db mid=5033395;msgid=5664003;creatAt=1422334250511
2015/01/27 12:50:52:947  void __sqlite_update_proc(void *, int, const char *, const char *, sqlite_int64) #359 [VERBOSE] __sqlite_update_hook operation=SQLITE_UPDATE, db=main, table=WKConversation, rowId=10

2015/01/27 12:50:52:947  void __sqlite_rollback_proc(void *) #375 [VERBOSE] __sqlite_rollback_hook
2015/01/27 12:50:52:947  <L_PUSH> __46-[WKReceiveMessageHandler pushReceived:value:]_block_invoke #136 [INFO] updateConversationSuccess;mid=5033395;cid=620947;msgid=5664003;tag=0

Anyone can tell me if sqlite3 would rollback a single sql insert and why. Thanks!