Running a transaction (#969)

* Start work on leveldb transactions

* Style

* Working API. Not plumbed in yet

* Move files into correct place

* Wrangling file locations and associations

* Tests pass

* Add some comments

* style

* Fix copyright

* Rewrite iterator internals to handle deletion-while-iterating. Also add tests for same

* Switch to strings instead of slices

* Style

* More style fixes

* Start switching writegroup over

* Swap out write group tracking for transaction usage

* Style

* Response to feedback before updating docs

* Style

* Add comment

* Initialize version_

* Satisfy the linter

* Start switching writegroup over

* Swap out write group tracking for transaction usage

* Style

* Checkpoint before implementing BatchDescription

* Style

* Initial plumbing for leveldb local parts

* Add model::BatchId

* Port leveldb_key.{h,cc}

* Add string StartsWith

* Add leveldb_key_test.cc to the project

* Revert back to using leveldb::Slice for read/describe

These operations universally operate on keys obtained from leveldb so
it's actually unhelpful to force all the callers to make
absl::string_views from them.

* Everything passing

* Drop unused function

* Style

* STart work on reads

* Swap reads in queryCache to use transactions

* Fix up tests of querycache

* Drop commented out code

* Cleanup

* Style

* Fix up for passing tests

* style

* Renaming

* Style

* Start work on ToString for transactions

* Add ToString() method to LevelDbTransaction

* Style

* lint

* Fix includes, drop runTransaction

* current_transaction -> currentTransaction

* LevelDbTransaction::NewIterator now returns a unique_ptr

* Style

* Revert addition of util::StartsWith

* Add log line

* Style

* Add log line

* Style

* Add debug log line for commits, drop unused BatchDescription

* STart work on reads

* Swap reads in queryCache to use transactions

* Start on remote documents

* Transition mutation queue and remote documents to use transactions

* Style

* Make everything pass

* Make everything pass

* Make it compile

* Style

* Style

* Revert name change, use DefaultReadOptions()

* Style

* Example of running a transaction with a lambda

* Drop errant typo

* Drop duplicate method declarations

* replace usage of auto w/ decltype

* Drop an unnecessary _Nullable. Add some nullability warning suppression

* use absl::make_unique, handle void return type

* Style

* Wrap backing persistence and expectation of backing persistence for transaction runner into a method

* More comments, trigger CI

1 files changed, 19 insertions, 1 deletions

diff --git a/Firestore/Source/Local/FSTLevelDB.mm b/Firestore/Source/Local/FSTLevelDB.mm
index 2edccb4..922c5b4 100644
--- a/Firestore/Source/Local/FSTLevelDB.mm
+++ b/Firestore/Source/Local/FSTLevelDB.mm
@@ -28,6 +28,7 @@
 #import "Firestore/Source/Remote/FSTSerializerBeta.h"
 #import "Firestore/Source/Util/FSTAssert.h"
 #import "Firestore/Source/Util/FSTLogger.h"
+#include "absl/memory/memory.h"
 
 #include "Firestore/core/src/firebase/firestore/auth/user.h"
 #include "Firestore/core/src/firebase/firestore/core/database_info.h"
@@ -62,6 +63,7 @@ using leveldb::WriteOptions;
 
 @implementation FSTLevelDB {
   std::unique_ptr<LevelDbTransaction> _transaction;
+  FSTTransactionRunner _transactionRunner;
 }
 
 /**
@@ -79,10 +81,15 @@ using leveldb::WriteOptions;
     _directory = [directory copy];
     _writeGroupTracker = [FSTWriteGroupTracker tracker];
     _serializer = serializer;
+    _transactionRunner.SetBackingPersistence(self);
   }
   return self;
 }
 
+- (const FSTTransactionRunner &)run {
+  return _transactionRunner;
+}
+
 + (NSString *)documentsDirectory {
 #if TARGET_OS_IPHONE
   NSArray<NSString *> *directories =
@@ -222,9 +229,20 @@ using leveldb::WriteOptions;
   return [[FSTLevelDBRemoteDocumentCache alloc] initWithDB:self serializer:self.serializer];
 }
 
+- (void)startTransaction {
+  FSTAssert(_transaction == nullptr, @"Starting a transaction while one is already outstanding");
+  _transaction = absl::make_unique<LevelDbTransaction>(_ptr.get());
+}
+
+- (void)commitTransaction {
+  FSTAssert(_transaction != nullptr, @"Committing a transaction before one is started");
+  _transaction->Commit();
+  _transaction.reset();
+}
+
 - (FSTWriteGroup *)startGroupWithAction:(NSString *)action {
   FSTAssert(_transaction == nullptr, @"Starting a transaction while one is already outstanding");
-  _transaction = std::make_unique<LevelDbTransaction>(_ptr.get());
+  _transaction = absl::make_unique<LevelDbTransaction>(_ptr.get());
   return [self.writeGroupTracker startGroupWithAction:action transaction:_transaction.get()];
 }