Module txn 

Process-level ACID primitives for MDQL.

Three layers:

1. atomic_write — crash-safe single-file write via temp+rename
2. table_lock — exclusive per-table lock via flock
3. multi_file_txn — write-ahead journal for multi-file operations

Structs

Journal

JournalEntry

TableLock

RAII guard for an exclusive table lock.

TableTransaction

Constants

JOURNAL_FILENAME

LOCK_FILENAME

TMP_SUFFIX

Functions

atomic_write

Write content to path atomically via temp file + rename.

recover_journal

If a journal exists from a crashed transaction, roll back. Returns true if recovery was performed.

with_multi_file_txn

Context manager equivalent — runs a closure within a transaction. On success, commits. On error, rolls back and re-raises.