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Documentation updates: - Fix v0.1.0 → v1.1.0 version numbers in en, ru, fa, zh docs - Add missing Window Functions, Multi-Tenant ERP, Supported Keywords sections to ru, fa, zh baraql.md (~105 lines each) - Expand Turkish and Arabic baraql.md (110 → 268 lines) - Expand Turkish and Arabic installation.md (62 → 307 lines) - Add new Bulgarian documentation files (18 new files) Client updates: - Python: Full async/await rewrite with asyncio, request queueing - Rust: Full async/await rewrite with tokio, async examples - Nim: Update README to v1.1.0 - All clients now support async patterns consistently
79 lines
2.1 KiB
Markdown
79 lines
2.1 KiB
Markdown
# Транзакции и MVCC
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MVCC (Multi-Version Concurrency Control) със snapshot изолация и deadlock детекция.
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## Употреба
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```nim
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import barabadb/core/mvcc
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var tm = newTxnManager()
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let txn = tm.beginTxn()
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# Операции за запис
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discard tm.write(txn, "key1", cast[seq[byte]]("value1"))
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discard tm.write(txn, "key2", cast[seq[byte]]("value2"))
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# Savepoint
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tm.savepoint(txn)
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discard tm.write(txn, "key3", cast[seq[byte]]("value3"))
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discard tm.rollbackToSavepoint(txn) # отмяна на key3
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# Commit
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discard tm.commit(txn)
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```
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## Изолация на Транзакции
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BaraDB използва **snapshot изолация**:
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- Четящите не блокират пишещите
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- Пишещите не блокират четящите
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- Всяка транзакция вижда консистентен snapshot
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## Deadlock Детекция
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```nim
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import barabadb/core/deadlock
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var detector = newDeadlockDetector()
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if detector.detectCycle(txn1, txn2):
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echo "Открит deadlock!"
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```
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## Write-Ahead Log
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```nim
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import barabadb/storage/wal
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var wal = newWAL("./wal")
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wal.append(txnId, "SET key value")
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wal.flush()
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```
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## Savepoints
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Вложени savepoints на транзакции:
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```nim
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tm.savepoint(txn, "sp1")
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# ... операции ...
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tm.rollbackToSavepoint(txn, "sp1")
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```
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## Формална Верификация
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MVCC / Snapshot Isolation протоколът е формално специфициран в TLA+:
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- **Спецификация:** `formal-verification/mvcc.tla`
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- **Проверени свойства:**
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- `NoDirtyReads` — транзакциите никога не четат некомитнати данни
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- `ReadOwnWrites` — транзакциите винаги виждат собствените си записи
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- `WriteWriteConflict` — first-committer-wins (няма две комитнати транзакции да пишат един и същ ключ)
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Пускане на TLC локално:
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```bash
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cd formal-verification
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java -cp tla2tools.jar tlc2.TLC -config models/mvcc.cfg mvcc.tla
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```
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