Add a dormant, best-effort v4 RDS Postgres dual-write to the CI benchmark emitters

.big-plans/ct__bench-v4-emitters--1-1-measurement-id.plan.md

@@ -0,0 +1,132 @@
+# Sub-phase 1.1 — measurement_id contract Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Port the three `measurement_id` contract files verbatim from branch ref `f9b36ae3f` into the monorepo working tree, repoint the cross-repo doc references, and verify byte-parity against the golden vectors.
+
+**Architecture:** This is an EXTRACT-FROM-BRANCH + ADJUST + VERIFY unit, not a from-scratch implementation. The files already exist on the unmerged branch and apply cleanly (mainline has never touched these paths). `scripts/_measurement_id.py` reproduces the Rust server's `measurement_id` xxhash64 hash; `scripts/test_measurement_id.py` pins it against `scripts/measurement_id_golden.json` (63 cross-language golden vectors over 5 fact tables).
+
+**Tech Stack:** Python 3.11+, the `xxhash` package (XXH64), pytest, `uv run --no-project --with ...`, ruff.
+
+## Global Constraints
+
+- Extract files VERBATIM from `f9b36ae3f` via `git show f9b36ae3f:<path> > <path>`. Do NOT re-author or alter any hash logic, field order, or golden value.
+- Repoint ONLY the cross-repo documentation references in the two `.py` docstrings (paths that no longer exist in this monorepo). No logic changes.
+- Both `.py` files MUST keep the two SPDX header lines: `# SPDX-License-Identifier: Apache-2.0` and `# SPDX-FileCopyrightText: Copyright the Vortex contributors` (already present on the branch).
+- Python lint: ruff `F,E,W,UP,I` clean; line-length 120. Comments use `--`, never em dashes; full sentences.
+- This sub-phase touches ONLY: `scripts/_measurement_id.py`, `scripts/measurement_id_golden.json`, `scripts/test_measurement_id.py`. Do NOT touch `ci.yml`, any workflow, or `post-ingest.py` (those are sub-phase 1.3 / 1.2).
+- Commits: DCO trailer `Signed-off-by: Connor Tsui <connor@spiraldb.com>`. Never put backticks or a `---` scissors line in a `git commit -m` message; use `git commit -F` with a heredoc.
+
+---
+
+### Task 1: Port the measurement_id contract files and verify golden parity
+
+**Files:**
+- Create: `scripts/_measurement_id.py` (extracted from `f9b36ae3f`)
+- Create: `scripts/measurement_id_golden.json` (extracted from `f9b36ae3f`)
+- Create/Test: `scripts/test_measurement_id.py` (extracted from `f9b36ae3f`)
+
+**Interfaces:**
+- Produces (relied on by sub-phases 1.2/1.3): `scripts/_measurement_id.py` exposing the dispatch dict `MEASUREMENT_ID_BY_TABLE` keyed by the five table names (`query_measurements`, `compression_times`, `compression_sizes`, `random_access_times`, `vector_search_runs`), each value a callable taking the table's dimensional fields as keyword args and returning a signed-i64 `measurement_id`. Sub-phase 1.2's Postgres writer imports this module to compute upsert keys.
+- Consumes: nothing from earlier tasks (this is the first sub-phase).
+
+- [ ] **Step 1: Extract the golden vectors and the test from the branch (the "test" half first, for a real red->green)**
+
+```bash
+cd "$(git rev-parse --show-toplevel)"
+git show f9b36ae3f:scripts/measurement_id_golden.json > scripts/measurement_id_golden.json
+git show f9b36ae3f:scripts/test_measurement_id.py > scripts/test_measurement_id.py
+```
+
+Do NOT edit `measurement_id_golden.json` at all (not even its `note` field): it is a Rust-generated artifact (regenerated by `REGEN_GOLDEN_VECTORS=1 cargo test -p vortex-bench-server --test measurement_id_golden` in the `vortex-data/benchmarks-website` repo). Editing it would drift the monorepo copy from the generator. Porting it byte-identical is what lets the test pin cross-language parity.
+
+- [ ] **Step 2: Run the test to verify it fails (the implementation module does not exist yet)**
+
+```bash
+uv run --no-project --with pytest --with xxhash pytest scripts/test_measurement_id.py -q
+```
+
+Expected: an ERROR during collection — `scripts/test_measurement_id.py` executes `port = _load_port()` at import time, which tries to load `scripts/_measurement_id.py`; that file does not exist yet, so collection fails (FileNotFoundError / module load error). This confirms the test is wired to the implementation.
+
+- [ ] **Step 3: Extract the implementation module from the branch**
+
+```bash
+git show f9b36ae3f:scripts/_measurement_id.py > scripts/_measurement_id.py
+```
+
+- [ ] **Step 4: Run the test to verify it passes (all 63 vectors + the 3 meta tests)**
+
+```bash
+uv run --no-project --with pytest --with xxhash pytest scripts/test_measurement_id.py -q
+```
+
+Expected: PASS — 63 parametrized `test_python_port_matches_golden` cases plus `test_all_tables_covered` and `test_multibyte_fixture_present`, all green (66 passed). If any vector mismatches, the port and the golden file disagree — STOP and report; do not edit values to force a pass.
+
+- [ ] **Step 5: Repoint the cross-repo doc references in `_measurement_id.py` (cosmetic; no logic change)**
+
+In `scripts/_measurement_id.py`, replace the single occurrence of the path token:
+
+- old: `` `benchmarks-website/server/src/db.rs` `` (in the module docstring, the "byte-for-byte port of" line)
+- new: ``the `vortex-data/benchmarks-website` repo's `server/src/db.rs` ``
+
+so the sentence reads "This is a byte-for-byte port of the `vortex-data/benchmarks-website` repo's `server/src/db.rs` (`measurement_id_*`, `hasher_for`, ...)". This is the only `benchmarks-website` reference in this file.
+
+- [ ] **Step 6: Repoint the cross-repo doc references in `test_measurement_id.py` (cosmetic; no logic change)**
+
+In `scripts/test_measurement_id.py` docstring, repoint both references:
+
+- `` `benchmarks-website/server/src/db.rs` `` -> ``the `vortex-data/benchmarks-website` repo's `server/src/db.rs` ``
+- `` `benchmarks-website/server/tests/measurement_id_golden.rs` `` -> ``the `vortex-data/benchmarks-website` repo's `server/tests/measurement_id_golden.rs` ``
+
+Do NOT alter the `import`s, the loader, or any assertion.
+
+- [ ] **Step 7: Re-run the test after the docstring edits (guard against an accidental code edit)**
+
+```bash
+uv run --no-project --with pytest --with xxhash pytest scripts/test_measurement_id.py -q
+```
+
+Expected: PASS (still 66 passed). The docstring edits must not change behavior.
+
+- [ ] **Step 8: Lint and format-check the two new Python files**
+
+```bash
+uvx ruff check scripts/_measurement_id.py scripts/test_measurement_id.py
+uvx ruff format --check scripts/_measurement_id.py scripts/test_measurement_id.py
+```
+
+Expected: both exit 0 (no diagnostics, already-formatted). If `ruff format --check` reports a diff, run `uvx ruff format scripts/_measurement_id.py scripts/test_measurement_id.py` and re-run Step 7 to confirm the test still passes.
+
+- [ ] **Step 9: Confirm SPDX headers are present on both `.py` files**
+
+```bash
+head -2 scripts/_measurement_id.py
+head -2 scripts/test_measurement_id.py
+```
+
+Expected: each begins with `# SPDX-License-Identifier: Apache-2.0` then `# SPDX-FileCopyrightText: Copyright the Vortex contributors`. (They are present on the branch; this is a guard.)
+
+- [ ] **Step 10: Commit**
+
+```bash
+git add scripts/_measurement_id.py scripts/measurement_id_golden.json scripts/test_measurement_id.py
+git commit -F - <<'EOF'
+scripts: add measurement_id Python port + golden-vector test
+
+Port the server-internal measurement_id xxhash64 hash to Python
+(scripts/_measurement_id.py) with its 63-vector cross-language golden test
+(scripts/test_measurement_id.py, scripts/measurement_id_golden.json), extracted
+verbatim from the v4 emitter branch. Repoint the docstrings to the extracted
+vortex-data/benchmarks-website repo. The golden vectors pin Rust == Python.
+
+Signed-off-by: Connor Tsui <connor@spiraldb.com>
+EOF
+```
+
+---
+
+## Self-Review
+
+- **Spec coverage:** all three files (`_measurement_id.py`, `measurement_id_golden.json`, `test_measurement_id.py`) are created (Steps 1, 3); docstrings repointed (Steps 5-6); SPDX verified (Step 9); parity verified (Steps 4, 7); lint clean (Step 8). Out-of-scope items (ci.yml, workflows, post-ingest.py) are untouched.
+- **Placeholder scan:** none — every step has an exact command or an exact old->new string.
+- **Type consistency:** the `MEASUREMENT_ID_BY_TABLE` dispatch and the five table names match the golden file's `table` values and what sub-phase 1.2 will import.