Series
Explore PostgreSQL internals in this series—learn how data is stored, queries run, and transactions work. Hands-on experiments and system-level insights help you master PostgreSQL like a backend engineer.
When you execute INSERT INTO users VALUES (1, 'Alice') in PostgreSQL, what actually happens on disk? Where does that data go? How is it organized? Why does a simple SELECTsometimes cause disk writes? These aren't just academic questions—they're the f...
When you create a table, PostgreSQL assigns it an OID (Object Identifier). This is just a logical identifier for the table. it is stored in the system catalog pg_class and remains constant for the lifetime of the table. But under the hood in physical...
From the previous blog we knew that tables are made up of 8KB pages, lets crack open a page and see what's really inside it. This is where the things get interesting because jargons like MVCC, tuple storage, visiblity rules, freespace is dependent on...
When you insert a new row into a table, postgreSQL creates a tuple, a contiguous chunk of memory bytes that contains both system metadata and your actual data. A tuple starts with a 23 byte header. Every single tuple in every table has this same head...
The main problem TOAST solves is fundamental : postgres pages are of 8kb, and tuple must fit within that page. so what happens if you try to insert 1MB of text field ? Without toast you would get an error: "Row too big". With toast PostgreSQL handles...
