Change write groups to use transactions (#912)

* 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

* Everything passing

* Drop unused function

* Style

* Renaming

* Style

* Add log line

* Style

* Add debug log line for commits, drop unused BatchDescription

2 files changed, 34 insertions, 44 deletions

diff --git a/Firestore/Example/Tests/Local/FSTLevelDBMigrationsTests.mm b/Firestore/Example/Tests/Local/FSTLevelDBMigrationsTests.mm
index 3559d5d..822e3ca 100644
--- a/Firestore/Example/Tests/Local/FSTLevelDBMigrationsTests.mm
+++ b/Firestore/Example/Tests/Local/FSTLevelDBMigrationsTests.mm
@@ -18,10 +18,10 @@
 #include <leveldb/db.h>
 
 #import "Firestore/Protos/objc/firestore/local/Target.pbobjc.h"
+#import "Firestore/Source/Local/FSTLevelDB.h"
 #import "Firestore/Source/Local/FSTLevelDBKey.h"
 #import "Firestore/Source/Local/FSTLevelDBMigrations.h"
 #import "Firestore/Source/Local/FSTLevelDBQueryCache.h"
-#import "Firestore/Source/Local/FSTWriteGroup.h"
 
 #include "Firestore/core/src/firebase/firestore/util/ordered_code.h"
 
@@ -29,6 +29,7 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
+using firebase::firestore::local::LevelDbTransaction;
 using firebase::firestore::util::OrderedCode;
 using leveldb::DB;
 using leveldb::Options;
@@ -60,43 +61,52 @@ using leveldb::Status;
 - (void)testAddsTargetGlobal {
   FSTPBTargetGlobal *metadata = [FSTLevelDBQueryCache readTargetMetadataFromDB:_db];
   XCTAssertNil(metadata, @"Not expecting metadata yet, we should have an empty db");
-  [FSTLevelDBMigrations runMigrationsOnDB:_db];
+  LevelDbTransaction transaction(_db.get());
+  [FSTLevelDBMigrations runMigrationsWithTransaction:&transaction];
+  transaction.Commit();
   metadata = [FSTLevelDBQueryCache readTargetMetadataFromDB:_db];
   XCTAssertNotNil(metadata, @"Migrations should have added the metadata");
 }
 
 - (void)testSetsVersionNumber {
-  FSTLevelDBSchemaVersion initial = [FSTLevelDBMigrations schemaVersionForDB:_db];
+  LevelDbTransaction transaction(_db.get());
+  FSTLevelDBSchemaVersion initial =
+      [FSTLevelDBMigrations schemaVersionWithTransaction:&transaction];
   XCTAssertEqual(0, initial, "No version should be equivalent to 0");
 
   // Pick an arbitrary high migration number and migrate to it.
-  [FSTLevelDBMigrations runMigrationsOnDB:_db];
-  FSTLevelDBSchemaVersion actual = [FSTLevelDBMigrations schemaVersionForDB:_db];
+  [FSTLevelDBMigrations runMigrationsWithTransaction:&transaction];
+  FSTLevelDBSchemaVersion actual = [FSTLevelDBMigrations schemaVersionWithTransaction:&transaction];
   XCTAssertGreaterThan(actual, 0, @"Expected to migrate to a schema version > 0");
 }
 
 - (void)testCountsQueries {
   NSUInteger expected = 50;
-  FSTWriteGroup *group = [FSTWriteGroup groupWithAction:@"Setup"];
-  for (int i = 0; i < expected; i++) {
-    std::string key = [FSTLevelDBTargetKey keyWithTargetID:i];
-    [group setData:"dummy" forKey:key];
+  {
+    // Setup some targets to be counted in the migration.
+    LevelDbTransaction transaction(_db.get());
+    for (int i = 0; i < expected; i++) {
+      std::string key = [FSTLevelDBTargetKey keyWithTargetID:i];
+      transaction.Put(key, "dummy");
+    }
+    // Add a dummy entry after the targets to make sure the iteration is correctly bounded.
+    // Use a table that would sort logically right after that table 'target'.
+    std::string dummyKey;
+    // Magic number that indicates a table name follows. Needed to mimic the prefix to the target
+    // table.
+    OrderedCode::WriteSignedNumIncreasing(&dummyKey, 5);
+    OrderedCode::WriteString(&dummyKey, "targetA");
+    transaction.Put(dummyKey, "dummy");
+    transaction.Commit();
+  }
+
+  {
+    LevelDbTransaction transaction(_db.get());
+    [FSTLevelDBMigrations runMigrationsWithTransaction:&transaction];
+    transaction.Commit();
+    FSTPBTargetGlobal *metadata = [FSTLevelDBQueryCache readTargetMetadataFromDB:_db];
+    XCTAssertEqual(expected, metadata.targetCount, @"Failed to count all of the targets we added");
   }
-  // Add a dummy entry after the targets to make sure the iteration is correctly bounded.
-  // Use a table that would sort logically right after that table 'target'.
-  std::string dummyKey;
-  // Magic number that indicates a table name follows. Needed to mimic the prefix to the target
-  // table.
-  OrderedCode::WriteSignedNumIncreasing(&dummyKey, 5);
-  OrderedCode::WriteString(&dummyKey, "targetA");
-  [group setData:"dummy" forKey:dummyKey];
-
-  Status status = [group writeToDB:_db];
-  XCTAssertTrue(status.ok(), @"Failed to write targets");
-
-  [FSTLevelDBMigrations runMigrationsOnDB:_db];
-  FSTPBTargetGlobal *metadata = [FSTLevelDBQueryCache readTargetMetadataFromDB:_db];
-  XCTAssertEqual(expected, metadata.targetCount, @"Failed to count all of the targets we added");
 }
 
 @end
diff --git a/Firestore/Example/Tests/Local/FSTWriteGroupTests.mm b/Firestore/Example/Tests/Local/FSTWriteGroupTests.mm
index edd05a3..871bd99 100644
--- a/Firestore/Example/Tests/Local/FSTWriteGroupTests.mm
+++ b/Firestore/Example/Tests/Local/FSTWriteGroupTests.mm
@@ -80,26 +80,6 @@ NS_ASSUME_NONNULL_BEGIN
   XCTAssertTrue(status.IsNotFound());
 }
 
-- (void)testDescription {
-  std::string key = [FSTLevelDBMutationKey keyWithUserID:"user1" batchID:42];
-  FSTPBWriteBatch *message = [FSTPBWriteBatch message];
-  message.batchId = 42;
-
-  FSTWriteGroup *group = [FSTWriteGroup groupWithAction:@"Action"];
-  XCTAssertEqualObjects([group description], @"<FSTWriteGroup for Action: 0 changes (0 bytes):>");
-
-  [group setMessage:message forKey:key];
-  XCTAssertEqualObjects([group description],
-                        @"<FSTWriteGroup for Action: 1 changes (2 bytes):\n"
-                         "  - Put [mutation: userID=user1 batchID=42] (2 bytes)>");
-
-  [group removeMessageForKey:key];
-  XCTAssertEqualObjects([group description],
-                        @"<FSTWriteGroup for Action: 2 changes (2 bytes):\n"
-                         "  - Put [mutation: userID=user1 batchID=42] (2 bytes)\n"
-                         "  - Delete [mutation: userID=user1 batchID=42]>");
-}
-
 - (void)testCommittingWrongGroupThrows {
   // If you don't create the group through persistence, it should throw.
   FSTWriteGroup *group = [FSTWriteGroup groupWithAction:@"group"];