MVCC

MVCC Explained

How PostgreSQL's Multi-Version Concurrency Control lets readers and writers avoid blocking each other by keeping multiple row versions and using visibility rul…

PostgreSQL Interview Questions

Prepare for PostgreSQL technical interviews with commonly asked questions on internals, transactions, indexing, and troubleshooting.

What is the Read Committed Isolation Level?

Read Committed is an isolation level that guarantees a transaction only ever sees data that has been committed by other transactions, eliminating dirty reads w…

What is MVCC (Multi-Version Concurrency Control)?

MVCC (Multi-Version Concurrency Control) is a concurrency-control technique where the database keeps multiple versions of a row so readers see a consistent sna…

Redo Log vs Undo Log: What is the Difference?

A redo log records the new value produced by a change so committed effects can be reapplied after a crash, while an undo log records the old value that existed…

What is the VACUUM Process in PostgreSQL?

VACUUM is a PostgreSQL maintenance operation that reclaims storage occupied by dead tuples — rows left behind by UPDATE and DELETE under PostgreSQL's MVCC mode…

How Do You Tune Autovacuum in PostgreSQL?

Tuning autovacuum means adjusting how aggressively and how frequently PostgreSQL's background autovacuum workers scan and clean each table, primarily by loweri…

What Causes Table Bloat and How Do You Fix It?

Table bloat is the accumulation of dead or wasted space inside a table's data pages — usually because updates and deletes leave dead tuples faster than autovac…

How Does PostgreSQL Clean Up Dead Tuples?

PostgreSQL cleans up dead tuples — old row versions left behind by UPDATE and DELETE under MVCC — through VACUUM (run manually or by the autovacuum daemon), wh…