Tau

A temporal database engine written in Zig. Data is modelled as typed functions of time rather than rows in tables.

Zero external dependencies. Requires only the Zig toolchain.

Core ideas

• Time is the primitive. Every entity exists within a TimeDomain. No timeless data.
• Series as functions. A Series(T) is a partial function τ → T | ⊥, mapping timestamps to typed values. See MATHS.md.
• Lenses for transformation. A Lens(In, Out) applies a pure function over a live Series without copying data.
• Immutable by composition. Change is expressed by composing new lenses, not by mutating existing series.
• Columnar storage. Series are backed by Segment blocks — contiguous, sorted, append-only timestamp and value columns with O(log n) point lookup.

Configuration

All configuration is in src/config.zig. Edit and recompile to change settings. No environment variables, no CLI flags, no runtime config files.

// src/config.zig
pub const server = struct {
    pub const port: u16 = 7701;
    pub const address: [4]u8 = .{ 127, 0, 0, 1 };
    pub const certificate: [32]u8 = .{ ... };
    // ...
};

pub const simulation = struct {
    pub const default_seed: u64 = 0;  // 0 = use system time
    pub const default_scenarios: u32 = 1;
    pub const default_mode: Mode = .quick;
    // ...
};

Build

Requires Zig 0.15 on Linux.

zig build              # compile all targets
zig build test         # run all tests

Server

zig build server       # starts on configured address:port

Default: 127.0.0.1:7701. See src/server/README.md for the wire protocol.

Simulation

Tiger Beetle style deterministic simulation testing. Runs scenarios with fault injection to find bugs.

zig build sim                            # run simulation
zig build sim -Doptimize=ReleaseFast     # optimised (faster)

Configure in src/config.zig:

• simulation.default_mode: quick, standard, century, or chaos
• simulation.default_scenarios: number of scenarios to run
• simulation.default_seed: seed for reproducibility (0 = random)

See src/sim/README.md for details.

Benchmarks

zig build bench                            # debug
zig build bench -Doptimize=ReleaseFast     # optimised

See src/bench/README.md.

Project structure

src/
├── config.zig       # All configuration (edit to configure)
├── root.zig         # Library root
├── core/            # Data model: Series, Segment, Lens
├── server/          # TCP database server
├── sim/             # Simulation testing framework
└── bench/           # Benchmark harness

Design documents

• MATHS.md — formal model: Series as partial functions, Lens as morphisms.
• TIGER_STYLE.md — coding style guide.