Code Structure

The following is the main directories of Postgres codebase.

src/backend
├── access
│   ├── heap
│   ├── index
│   └── transam
├── catalog
├── executor
├── main
├── optimizer
├── parser
├── postmaster
└── storage
    ├── buffer
    ├── file
    ├── ipc
    ├── lmgr
    └── smgr

We will first look at storage and access. The former is responsible for managing pages on disk and their buffers in shared memory. The latter concerns the formats within a page, whether it is a heap table, B-tree index, or WAL log. The separation of page management and page format is convenient for extending access methods or storage. The following are examples:

• pgvector is an extension that provides support for storing vector indexes inside Postgres.
• neon is a distributed database built on top of Postgres. It replaces local disk management with S3-based page servers.