| # Cross-DBMS verification: PostgreSQL 16.15 |
|
|
| Status: the evaluation mechanism was re-run on PostgreSQL for the 12 seed families on |
| 2026-10-19. Full-corpus PostgreSQL evidence is not published in v0.2.0; this document |
| records the portability check and its limits. |
|
|
| ## What was verified |
|
|
| The published MySQL evidence for the 12 seed families of the library schema was |
| recomputed on PostgreSQL 16.15 from the same inputs: |
|
|
| | Input | Value | |
| |---|---| |
| | Corpus | `data/corpus/families.json` (12 families, unchanged reference SQL) | |
| | State bank | `data/states/states.json`, the same 28 states | |
| | Model answers | the saved runs in `data/runs/` (three seed models, unchanged) | |
| | DBMS | PostgreSQL 16.15 (previous series preflight used the same version) | |
| | DDL | the corpus DDL, executed without any adaptation | |
| | Reference executions | 12 families × 28 states = 336 | |
| | Candidate checks | 12 families × 28 states × 3 models = 1 008 | |
|
|
| For every state the reference and the candidate were executed read-only in a clean |
| private schema, and the resulting row lists were compared; the per-(model, family, state) |
| outcome was then compared with the refuting-state sets published in `data/evidence/`. |
|
|
| ## Result |
|
|
| - **DDL adaptation required: none.** The library DDL (`INTEGER PRIMARY KEY`, |
| `VARCHAR` lengths, inline foreign keys) and all 12 reference queries executed on |
| PostgreSQL unchanged. |
| - **Status mismatches with the MySQL evidence: 0** of 1 008 candidate checks. |
|
|
| The raw check record is stored in [cross_dbms_seed_check.json](cross_dbms_seed_check.json). |
| No per-state rows or pins are duplicated there; the record is a verification log, not a |
| second evidence bank. |
|
|
| ## Why the comparison is meaningful, and what it does not show |
|
|
| - Equivalence is checked **within one engine**: the reference and the candidate run on the |
| same DBMS, so engine-specific row order rules do not affect the verdict. MySQL sorts |
| NULLs first in ascending order and PostgreSQL sorts them last, so the *ordering of rows |
| in a witness* can differ between engines; the refuting state and the multiset difference |
| do not. |
| - The check covers the 12 seed families only. It shows that the mechanism ports, not that |
| every family in the corpus behaves identically on PostgreSQL. In particular, queries |
| with engine-specific functions would need dialect review before a full PostgreSQL run. |
| - The dataset format stores one `dbms` per evidence file. Adding a second engine as |
| first-class evidence requires a format extension (separate evidence per engine or a |
| `dbms` field per record) and is left for the next version. |
|
|
