Fix duckdb#9342: WAL - instead of using FileExists -> OpenFile, use O…

…penFile with FILE_FLAGS_NULL_IF_NOT_EXISTS

src/common/serializer/buffered_file_reader.cpp

@@ -57,6 +57,12 @@ void BufferedFileReader::Seek(uint64_t location) {
 	read_data = offset = 0;
 }
 
+void BufferedFileReader::Reset() {
+	handle->Reset();
+	total_read = 0;
+	read_data = offset = 0;
+}
+
 uint64_t BufferedFileReader::CurrentOffset() {
 	return total_read + offset;
 }

src/include/duckdb/common/serializer/buffered_file_reader.hpp

@@ -34,6 +34,8 @@ class BufferedFileReader : public ReadStream {
 		return file_size;
 	}
 
+	//! Resets reading - beginning at position 0
+	void Reset();
 	void Seek(uint64_t location);
 	uint64_t CurrentOffset();
 

src/include/duckdb/storage/write_ahead_log.hpp

@@ -52,7 +52,7 @@ class WriteAheadLog {
 
 public:
 	//! Replay the WAL
-	static bool Replay(AttachedDatabase &database, string &path);
+	static bool Replay(AttachedDatabase &database, unique_ptr<FileHandle> handle);
 
 	//! Returns the current size of the WAL in bytes
 	int64_t GetWALSize();

src/storage/storage_manager.cpp

@@ -171,9 +171,10 @@ void SingleFileStorageManager::LoadDatabase() {
 
 		// check if the WAL file exists
 		auto wal_path = GetWALPath();
-		if (fs.FileExists(wal_path)) {
+		auto handle = fs.OpenFile(wal_path, FileFlags::FILE_FLAGS_READ | FileFlags::FILE_FLAGS_NULL_IF_NOT_EXISTS);
+		if (handle) {
 			// replay the WAL
-			if (WriteAheadLog::Replay(db, wal_path)) {
+			if (WriteAheadLog::Replay(db, std::move(handle))) {
 				fs.RemoveFile(wal_path);
 			}
 		}

src/storage/wal_replay.cpp

@@ -158,10 +158,10 @@ class WriteAheadLogDeserializer {
 //===--------------------------------------------------------------------===//
 // Replay
 //===--------------------------------------------------------------------===//
-bool WriteAheadLog::Replay(AttachedDatabase &database, string &path) {
+bool WriteAheadLog::Replay(AttachedDatabase &database, unique_ptr<FileHandle> handle) {
 	Connection con(database.GetDatabase());
-	auto initial_source = make_uniq<BufferedFileReader>(FileSystem::Get(database), path.c_str());
-	if (initial_source->Finished()) {
+	BufferedFileReader reader(FileSystem::Get(database), std::move(handle));
+	if (reader.Finished()) {
 		// WAL is empty
 		return false;
 	}
@@ -174,10 +174,10 @@ bool WriteAheadLog::Replay(AttachedDatabase &database, string &path) {
 	try {
 		while (true) {
 			// read the current entry (deserialize only)
-			auto deserializer = WriteAheadLogDeserializer::Open(checkpoint_state, *initial_source, true);
+			auto deserializer = WriteAheadLogDeserializer::Open(checkpoint_state, reader, true);
 			if (deserializer.ReplayEntry()) {
 				// check if the file is exhausted
-				if (initial_source->Finished()) {
+				if (reader.Finished()) {
 					// we finished reading the file: break
 					break;
 				}
@@ -196,7 +196,6 @@ bool WriteAheadLog::Replay(AttachedDatabase &database, string &path) {
 		Printer::Print("Unknown Exception in WAL playback during initial read");
 		return false;
 	} // LCOV_EXCL_STOP
-	initial_source.reset();
 	if (checkpoint_state.checkpoint_id.IsValid()) {
 		// there is a checkpoint flag: check if we need to deserialize the WAL
 		auto &manager = database.GetStorageManager();
@@ -208,9 +207,11 @@ bool WriteAheadLog::Replay(AttachedDatabase &database, string &path) {
 	}
 
 	// we need to recover from the WAL: actually set up the replay state
-	BufferedFileReader reader(FileSystem::Get(database), path.c_str());
 	ReplayState state(database, *con.context);
 
+	// reset the reader - we are going to read the WAL from the beginning again
+	reader.Reset();
+
 	// replay the WAL
 	// note that everything is wrapped inside a try/catch block here
 	// there can be errors in WAL replay because of a corrupt WAL file

test/sql/storage/concurrent_attach.test_slow

@@ -0,0 +1,34 @@
+# name: test/sql/storage/concurrent_attach.test_slow
+# description: Test concurrent attaching
+# group: [storage]
+
+concurrentforeach name foo bar
+
+statement ok
+attach '__TEST_DIR__/${name}.duckdb' AS ${name}
+
+statement ok
+create table ${name}.${name}(${name} bigint)
+
+loop i 0 1000
+
+statement ok
+insert into ${name}.${name} select sum(i) from range((random()*1000000.0)::INT) r(i)
+
+statement ok
+checkpoint ${name}
+
+statement ok
+detach ${name}
+
+statement ok
+attach '__TEST_DIR__/${name}.duckdb' AS ${name}
+
+endloop
+
+query I
+select count(*) FROM ${name}.${name}
+----
+1000
+
+endloop