v0.3.0 — the numbers stop being wrong

[0.3.0] — 2026-07-26

The numbers stop being wrong, and the city stops looking like a night raid.

Fixed — the simulator

• Bottlenecks are reachable at last. A batch controller was silently
  cancelling every constraint in the model: sweeping the workload knob from 1 to
  50,000 tps returned 90–100% of what was offered every time, and breaking
  everything at once — 32 buffers, lock contention, no background writer,
  remote_apply at 400 ms, no autovacuum — still committed 4,724 transactions a
  second. The causes were all simulated correctly; only the effect was
  unreachable. Achieved throughput now emerges from the model's own limits:
  measured over ten simulated minutes at the shipped defaults, 10 tps offered
  yields 7 achieved, with nine checkpoints and five autovacuum runs.
• WAL-triggered checkpoints fire at the right threshold. PostgreSQL uses
  max_wal_size / (1 + checkpoint_completion_target) — about 53% of
  max_wal_size at the default — per CalculateCheckPointSegments() in
  xlog.c. The model used the whole of max_wal_size, and the countdown
  estimate carried the same error. Both now call one shared function, so the
  display cannot drift from the behaviour.
• The cache hit gauge is computed the way pg_stat_database computes it —
  blks_hit / (blks_hit + blks_read) — rather than as a time-average of ratios.
  Measured at steady state it reads 87%, against 57% before.
• Vacuum is charged WAL and I/O instead of being free theatre; truncation
  returns only trailing empty pages; the autovacuum launcher no longer starves
  large tables behind small hot ones.

Fixed — the city was telling lies

• Local memory is part of each backend, not a building beside them.
  work_mem, maintenance_work_mem and temp_buffers were drawn as one shared
  structure next to the backend row. The prose said "per backend" and the
  geometry said otherwise, and geometry wins: a visitor who correctly reads the
  plaza as "one shared thing every process maps" then meets a second,
  similar-looking memory building and reasonably concludes the wrong thing.
• shared_buffers no longer claims a maximum of 8 MiB. The slider was
  labelled with the literal tile count, so its ceiling was 1,024 × 8 KiB — a
  size nobody runs. The pool is now sized in realistic units and the 1,024 tiles
  are declared as what they are: a 1,024-frame sample of the page cache.
• The plaza is called the buffer pool, which is the structure;
  shared_buffers is the parameter that sizes it.

Changed — it no longer reads as an aerial assault

• The walsender was a 49 m transmission tower with a parabolic dish, a feed
  horn, expanding torus pulses launched along the aim vector, and a blinking
  crimson beacon. Under load it read as a muzzle blast. It is now a cable head
  topping out at 16.1 m — the same height as its neighbours.
• The standby's read-only client was a ringed disc at 34 m with a lit beam
  angling down onto the deck. It is a terminal at grade with its read path along
  the ground.
• Nothing was deleted outright; every mechanism was re-housed. The push that
  spawned the torus pulses now advances a ratchet on the replication slot drum,
  one tooth per chunk. The archive backlog strobe became a steady lamp whose
  brightness is the queue depth — strictly more informative than a flash,
  since it was previously black except when critical.
• Forty-three translucent materials had turned the city to fog with no
  silhouettes. Opacity is now a semantic tier rather than atmosphere.

Added

• A daylight theme. The night model is "structure matte, meaning neon, only
  neon blooms", which inverts under a bright sky — so daylight is toon shading,
  ink lines, bloom off, sun and shadows, with every semantic colour re-derived
  to hold its meaning on a light background.
• Open a page and read it. A heap page can be opened to its real layout:
  the header with pd_lower and pd_upper, the line pointer array growing
  forward with LP_NORMAL / LP_REDIRECT / LP_DEAD distinguished, free space
  in the middle, and tuples growing backward from the end — with a tuple
  header opened to t_xmin, t_xmax and t_ctid, where MVCC visibility
  actually lives. The data directory gets the same treatment.
• Walk mode has a floor. It believed it was standing on something 76 m in
  the air, which is why it felt like flying. Plus procedural footstep audio,
  synthesised rather than sampled — no assets, no dependency — with cadence
  driven by distance travelled, so it is correct at every gait and stops dead
  when you stop.
• Backups, PITR and failover, sited off the primary as they must be: an
  archive estate with a timeline switchyard where the live timeline is the
  through line and every fork is a siding that never rejoins, a recovery ground
  on separate iron, and an HA quarter with a consensus store holding the lock
  and no user data.
• Touch works properly — one finger pans, two fingers pinch to zoom, twist
  to turn and drag to tilt. Mobile is usable: worst-case chrome coverage at
  390×844 went from 87.9% of the viewport to 48.9%, horizontal overflow from 26
  elements to none, and touch targets under 44 px from 49 to none.
• Left-drag pans and right-drag orbits — map convention rather than CAD.

Known issues

• The cache hit ratio is 87%, not the 98–99% a real OLTP database shows.
  Much better than the 57% of v0.2.0, and the gauge is now computed correctly,
  but the working set is still sized so the pool cannot dominate it.
• Achieved throughput sits at 70% of offered at the defaults. Some shortfall is
  honest — a real database does not serve everything it is asked — but this has
  not been calibrated against anything.
• The elephant-shaped ground plate is derived from the real logo artwork; judge
  the likeness for yourself from the plan view.
• Mobile is verified in Chrome emulation with touch, not on a real iPhone.