Added save points for transactions C API

Summary:
Added possibility to set save points in transactions and then rollback to them
Closes https://github.com/facebook/rocksdb/pull/2876

Differential Revision: D5825829

Pulled By: yiwu-arbug

fbshipit-source-id: 62168992340bbcddecdaea3baa2a678475d1429d

db/c.cc

@@ -3340,6 +3340,14 @@ void rocksdb_transaction_rollback(rocksdb_transaction_t* txn, char** errptr) {
   SaveError(errptr, txn->rep->Rollback());
 }
 
+void rocksdb_transaction_set_savepoint(rocksdb_transaction_t* txn) {
+  txn->rep->SetSavePoint();
+}
+
+void rocksdb_transaction_rollback_to_savepoint(rocksdb_transaction_t* txn, char** errptr) {
+  SaveError(errptr, txn->rep->RollbackToSavePoint());
+}
+
 void rocksdb_transaction_destroy(rocksdb_transaction_t* txn) {
   delete txn->rep;
   delete txn;

db/c_test.c

@@ -1463,6 +1463,25 @@ int main(int argc, char** argv) {
     CheckNoError(err);
     CheckTxnDBGet(txn_db, roptions, "bar", NULL);
 
+    // save point
+    rocksdb_transaction_put(txn, "foo1", 4, "hi1", 3, &err);
+    rocksdb_transaction_set_savepoint(txn);
+    CheckTxnGet(txn, roptions, "foo1", "hi1");
+    rocksdb_transaction_put(txn, "foo2", 4, "hi2", 3, &err);
+    CheckTxnGet(txn, roptions, "foo2", "hi2");
+
+    // rollback to savepoint
+    rocksdb_transaction_rollback_to_savepoint(txn, &err);
+    CheckNoError(err);
+    CheckTxnGet(txn, roptions, "foo2", NULL);
+    CheckTxnGet(txn, roptions, "foo1", "hi1");
+    CheckTxnDBGet(txn_db, roptions, "foo1", NULL);
+    CheckTxnDBGet(txn_db, roptions, "foo2", NULL);
+    rocksdb_transaction_commit(txn, &err);
+    CheckNoError(err);
+    CheckTxnDBGet(txn_db, roptions, "foo1", "hi1");
+    CheckTxnDBGet(txn_db, roptions, "foo2", NULL);
+
     // Column families.
     rocksdb_column_family_handle_t* cfh;
     cfh = rocksdb_transactiondb_create_column_family(txn_db, options,

include/rocksdb/c.h

@@ -1292,6 +1292,12 @@ extern ROCKSDB_LIBRARY_API void rocksdb_transaction_commit(
 extern ROCKSDB_LIBRARY_API void rocksdb_transaction_rollback(
     rocksdb_transaction_t* txn, char** errptr);
 
+extern ROCKSDB_LIBRARY_API void rocksdb_transaction_set_savepoint(
+    rocksdb_transaction_t* txn);
+
+extern ROCKSDB_LIBRARY_API void rocksdb_transaction_rollback_to_savepoint(
+    rocksdb_transaction_t* txn, char** errptr);
+
 extern ROCKSDB_LIBRARY_API void rocksdb_transaction_destroy(
     rocksdb_transaction_t* txn);