What is PLOMID?

PLOMID is a database engine written in Rust (crates/* workspace, unsafe_code = "forbid"). It owns its parser, planner surface, executor, MVCC, storage, WAL, and PostgreSQL-protocol frontend. It does not embed another database engine (deny.toml enforces this; see Repo structure).

Mental model#

flowchart LR
    Client["psql / DBeaver / any PG client"] -->|PG wire v3| Server["plomid-server\ncrates/server + network"]
    Server --> Exec["Executor\ncrates/executor"]
    Exec --> Txn["Transactions + MVCC\ncrates/txn + mvcc"]
    Exec --> Idx["Indexes\ncrates/index"]
    Txn --> Store["Storage + WAL\ncrates/storage + wal"]

flowchart LR
    Client["psql / DBeaver / any PG client"] -->|PG wire v3| Server["plomid-server\ncrates/server + network"]
    Server --> Exec["Executor\ncrates/executor"]
    Exec --> Txn["Transactions + MVCC\ncrates/txn + mvcc"]
    Exec --> Idx["Indexes\ncrates/index"]
    Txn --> Store["Storage + WAL\ncrates/storage + wal"]

A request moves: parse (crates/sql) → execute (crates/executor) → transact (crates/txn, crates/mvcc) → index/storage (crates/index, crates/storage) → persist (WAL + checkpoint). Details: Request lifecycle.

What PLOMID is / is not (v0.1.0)#

Evidence: workspace Cargo.toml (19 crates), crates/optimizer/src/lib.rs is a stub (no cost-based planner in v0.1.0 — EXPLAIN reports sequential scans), crates/security is foundations only (auth lives in crates/network).

Data model in one paragraph#

Databases contain schemas contain tables. Columns are PostgreSQL-typed (int4, text, numeric, json/jsonb, timestamptz, … — see Types). Rows are versioned by MVCC. Indexes (B-tree persistent, ART in-memory) accelerate equality, range, ordering, and uniqueness. JSON columns mix document and relational access in one query. Time columns use ordinary B-tree ordering plus zone-map/BRIN pruning on columnar data.

Next steps#

• Installation · Quickstart
• Core concepts · Data model
• Architecture overview