postgresqlHow can I use Postgresql's Write Ahead Logging (WAL) feature?

Postgresql's Write Ahead Logging (WAL) feature is a data protection mechanism that ensures the durability and consistency of the database. It helps to ensure that data is not lost in case of a system crash or power failure.

WAL works by logging all changes made to the database in a separate log file. This file is then used to replay all changes in the event of a system crash or power failure.

Example code

CREATE TABLE my_table (
    id INTEGER PRIMARY KEY,
    name VARCHAR(20)
);

BEGIN;
INSERT INTO my_table VALUES (1, 'John');
COMMIT;

In this example, Postgresql will first log the CREATE TABLE statement to the WAL file before executing it. Then, it will log the INSERT statement to the WAL file before executing it. Finally, it will log the COMMIT statement to the WAL file before committing the transaction.

If the system crashes or power fails after the INSERT statement is logged, but before it is committed, the INSERT statement will be replayed from the WAL file when the system is restarted. This ensures that the data is not lost.

Code explanation

• CREATE TABLE: Creates a new table in the database.
• BEGIN: Starts a new transaction.
• INSERT: Inserts a new row into the table.
• COMMIT: Commits the transaction.

Helpful links

• PostgreSQL Documentation - Write Ahead Logging
• PostgreSQL Documentation - Transactions

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