---
id: docs-pg-identifier-truncation-note
name: Document the pg identifier-truncation collision in the release text (review 004 item 13)
status: completed
depends_on: []
scope: single
risk: trivial
impact: isolated
level: implementation
tags: [review-004-fixes, postgres-engine, docs]
---

## Description

The pg identifier-truncation cross-channel collision, per
`docs/reviews/004-pre-release-general-review.md` §"Findings recorded,
not fixed" item 13: `LISTEN`/`UNLISTEN` interpolate the channel as a
quoted identifier (truncated at 63 bytes server-side) while
`pg_notify` carries it as a parameter — two distinct names sharing a
63-byte prefix can silently collapse into one wake channel. Names are
unbounded by the validation contract (the no-cap "length-independence"
verdict is deliberate — do not change it; the honest cheap fix is the
doc note the review prescribed).

Land the note in `deployment.md` (the pg rows / wherever the matrix
discusses naming or limits) and in `engine-postgres.md` if it has a
wake-channel section. The note states the mechanism (63-byte
identifier truncation; the `pg_notify` payload path unaffected) and
the mitigation (keep mechanism names under the PG identifier limit).
The deployment matrix is stable release text — a dated amendment
annotation per the family's convention.

## Acceptance Criteria

- [x] `deployment.md` carries the truncation-collision note with a
      dated annotation (mechanism + mitigation, honestly worded)
- [x] `engine-postgres.md` carries it too if a wake-channel section
      exists there (or the absence recorded in Notes)
- [x] The validation contract's no-cap verdict untouched
- [x] Doc gate green

## References

- docs/reviews/004-pre-release-general-review.md §"Findings recorded,
  not fixed" item 13 (the finding, the "fold into whichever doc pass
  runs next" disposition this task discharges)
- docs/architecture/deployment.md, engine-postgres.md (the landing
  sites)
- alkstore-postgres/src/forwarder.rs (the LISTEN/UNLISTEN
  interpolation sites, for the note's accuracy)

## Notes

Deployment matrix note: `deployment.md` has no standalone wake-channel
section — the landing site is the Postgres engine's co-tenancy
paragraph under "Connection budgets" (the one place the matrix
discusses naming), as a dated amendment annotation per the family
convention. `engine-postgres.md` has no dedicated wake-channel section
either; the note landed at the end of "Connection architecture" (the
wake substrate lives there) with a cross-reference to the
deployment-matrix statement. Accuracy sharpening beyond the review's
text (verified against Postgres master `commands/async.c`):
`pg_notify` does not merely escape identifier truncation — the server
*rejects* channels of 64 bytes or more there ("channel name too
long", an error), while quoted identifiers on the `LISTEN` side
truncate to 63 bytes silently (a `NOTICE`); the notes state the
collapse is on the registration side. The mitigation is phrased as a
consumer obligation (names at most 63 bytes; a byte count, not a
character count) — no validation contract change, per the task
description.

## Summary

Landed the pg identifier-truncation collision note in
`docs/architecture/deployment.md` (dated annotation, Postgres engine
section) and `docs/architecture/engine-postgres.md` (connection
architecture, wake-substrate section) — mechanism, honest send-vs-
registration-side statement, and the keep-names-under-63-bytes
mitigation. Frontmatter `last_updated` of both files carried forward.
Verified: `RUSTDOCFLAGS="-D warnings" cargo doc --no-deps` green,
`cargo fmt --check` green, `cargo clippy --all-targets -- -D warnings`
green; `core-contract.md`'s no-cap naming verdict untouched (diff
touching only the two doc files).