# MariaDB document-index collation repair

Finding **P9-REQUAL-DB01**, discovered during the actual MariaDB workload's preflight:
`GET /api/documents` returned500 with `Illegal mix of collations for operation 'UNION'`.
The timed workload did not start. Its250 synthetic applications and canonical profile were in
an owned generated schema; cleanup confirmed that schema absent. This is a reproduced provider
defect, separate from RD21 stale-save safety and from the earlier fixture setup errors.

The startup-created schema contains different text collations across the document name columns.
`DocumentsIndexService` combines CV names, job titles, attachment names, submitted-package names
and email subjects through seven `UNION ALL` projections. The failing query did not establish a
common name collation. The previous32-provider-case suite did not exercise this index.

Commit `2b26953d6f3c3fdacdffefa2c0a696c9084f1afd` applies explicit
`CONVERT(expression USING utf8mb4) COLLATE utf8mb4_bin` to those **read-only name projections**.
The binary collation retains the existing explicit lowercase/Nordic fold and accent-sensitive
search behavior; a general accent-insensitive collation would change that contract. Every SQL
expression is a compile-time source expression. Owner/search/filter values stay parameters.
Tenant joins, metadata/content exclusion, API response shape, stored values, table collations,
migrations and the SQLite expressions are unchanged.

Three new real-provider tests use the existing startup/version/schema guards. Before the fix,
the same three cases fail on the UNION collation error; after it they pass. They cover:

- Actual mixed startup collations and all seven source types, total/page/order agreement,
  recorded metadata, excluded content and independent unchanged persisted snapshots.
- Unicode accent sensitivity, literal `%`, `_`, `!`, deterministic ties and metadata-only search.
- Owner isolation, foreign/damaged associations, foreign history exclusion and filters.

Targeted RED/GREEN reports remain in
`.artifacts/p9-requal-01/documents-provider-{red,green}/mariadb.trx` and `tests.log`.
These targeted results are not added to the full suite. The fresh full successor is **35/35**
MariaDB cases with zero failures/skips; full backend **1123/1123** also passes. The normal push
and remote equality at this source checkpoint were verified; `main` remains `5f835e54a9b74e6b71418422e28431b2af06453f`.

Independent review checked the service, controller validation, three tests and both retained TRX
reports and found no actionable issues. Broader fresh browser, workload and output successors are
reported separately in the final addendum; this repair alone is not Phase9 or production acceptance.