sspl-migration-review

Date: 2026-09-13. Status: superseded.

Decision. Version 2.0.1 reconciles the migration. Pin SSPL 2026/2 (230103 rows, 161822 live, 187490 small users, 42613 large users); update the two Scottish Parliament columns to 2026 and main schema to postcode_simd_sspl_v2. Default SQL reads main; create_latest_postcode_lookup_history.sql is the explicit SPD alternative. Both share the two edition queries and return index_source, index_release, allocation and requested_link_postcode. SSPL accepts a linked A suffix only for a flagged small-user split representative; B/C cannot resolve. Never fall back across products. Correct the comparison selection and remove unsupported causal/PHS-parity claims.

Reason. The implementation, decision log and examples must agree. Preserve the SPD history fingerprint independently of an SSPL refresh, and check the new main fingerprint only against its own reviewed source pins and schema. Keep historical plans clearly superseded.

Evidence. tests/test_agreement.py checks synthetic and real SQL parity; tests/test_sql_sspl.py covers SSPL-only links, exclusions, era boundaries and row preservation; build/audit read back both saved tables against pinned sources. Original SSPL 2026/1 archive hash b8bc805567a167dd23a8891dddf44855a8174ddff3885c7f3caa0defc8d83478 and row fingerprint 6c14f4596b3fabb2c814d0af945eae02e00ea330f7440791437990ef4d98aa0f are retained as historical evidence.