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Transaction Management

SereneDB supports ACID database transactions. Transactions provide isolation, i.e., changes made by a transaction are not visible from concurrent transactions until it is committed. A transaction can also be aborted, which discards any changes it made so far.

Statements​

SereneDB provides the following statements for transaction management.

Starting a Transaction​

To start a transaction, run:

Query
BEGIN TRANSACTION;

Committing a Transaction​

You can commit a transaction to make it visible to other transactions and to write it to persistent storage (if using SereneDB in persistent mode). To commit a transaction, run:

Query
COMMIT;

If you are not in an active transaction, the COMMIT statement will fail.

Rolling Back a Transaction​

You can abort a transaction. This operation, also known as rolling back, will discard any changes the transaction made to the database. To abort a transaction, run:

Query
ROLLBACK;

You can also use the abort command, which has an identical behavior:

Query
ABORT;

If you are not in an active transaction, the ROLLBACK and ABORT statements will fail.

Multi-Statement Transactions​

When multiple SQL statements are submitted together (e.g., separated by semicolons), they are executed within a single implicit transaction. If any statement fails, all preceding statements in the batch are rolled back. This also applies to PRAGMA commands that decompose into multiple internal operations, such as COPY FROM DATABASE.

Isolation Level​

SereneDB's concurrency model guarantees snapshot isolation. Transactions that violate this isolation level are aborted.

Using PostgreSQL's transaction isolation levels, SereneDB guarantees repeatable reads.

Example​

We illustrate the use of transactions through a simple example.

Query
CREATE TABLE person (name VARCHAR, age BIGINT);
BEGIN TRANSACTION;
INSERT INTO person VALUES ('Ada', 52);
COMMIT;
BEGIN TRANSACTION;
DELETE FROM person WHERE name = 'Ada';
INSERT INTO person VALUES ('Bruce', 39);
ROLLBACK;
SELECT * FROM person;
Result
 name | age------+----- Ada  |  52

The first transaction (inserting “Ada”) was committed but the second (deleting “Ada” and inserting “Bruce”) was aborted. Therefore, the resulting table will only contain <'Ada', 52>.