openehr-mariadb

openEHR® persistence for MariaDB 11.4 — the schema dialect.

openEHR® is the registered trademark of the openEHR Foundation and is used with the permission of openEHR International. Use of the trademark does not constitute endorsement of this product by openEHR International or openEHR Foundation.

Conformance level: Schema#

This crate emits DDL for the shared openEHR schema, and a MariaDB 11.4 server has executed it: five tables, seven indexes, idempotent on re-application, foreign keys enforced, and both append-only tables refusing UPDATE and DELETE with a row present and intact afterwards.

../openehr-store/scripts/verify-schema.sh mariadb

CI runs the same script on every push. The level is Schema rather than Verified because this crate has no Store, not because the check is unverified. See spec/audit.md W-02.

It does not contain a store. There is no driver dependency, no connection handling, and no implementation of Store. Schema level means the database accepts the schema, not that this crate can talk to it.

See spec/index.md for what each level means and why they are stated this bluntly.

use openehr_mariadb::MariadbDialect;
use openehr_store::ddl_script;

println!("{}", ddl_script(&MariadbDialect));

This crate was `openehr-mysql` wearing a different name#

Worth stating plainly, because the corrected version below is only meaningful against it. Until 2026-08-01 this crate:

emitted byte-identical DDL to openehr-mysql (both hashed to 40f32f64e5015f8640830a67aecb9c72);
exported a public struct named MysqlDialect;
claimed Schema level against "MariaDB 8.4" — a release that has never existed, MariaDB having gone 10.x then 11.x;
told readers to reproduce it with a script that answered FAIL: unknown engine 'mariadb';
and described MariaDB as rejecting CREATE INDEX IF NOT EXISTS, which is true of MySQL and false of MariaDB.

It survived because openehr-sqlite/tests/dialects.rs — the test whose entire purpose is to fail when two dialects emit the same schema — compared five dialects, and this was the sixth. A comparison that omits a dialect cannot find it identical to another.

All of it is fixed, and the record is kept in spec/audit.md W-01 rather than quietly deleted.

Install#

[dependencies]
openehr-mariadb = "0.8"
openehr-store = "0.8"

Requires Rust 1.96+ (edition 2024).

What this crate owns#

Four things: type spellings, identifier quoting, placeholder style, and how the engine enforces append-only. Everything else — which tables exist, which columns, which indexes, the projection from openEHR objects onto rows, the commit rules, the conformance suite — lives in openehr-store and is shared by all six engines.

MariaDB is not MySQL, and here is where that is decided#

Two differences, both real engine facts rather than cosmetic edits, and both covered by a test that fails if this crate drifts back into being a copy:

MariaDB 11.4	MySQL 8.4	Consequence here
`CREATE INDEX IF NOT EXISTS` (since 10.0.5)	not supported	indexes are their own statements, not folded into `CREATE TABLE`
`CREATE OR REPLACE TRIGGER` (since 10.1.4)	not supported	no drop-then-create window in which the table is unprotected

The second is the one that matters. MySQL must DROP TRIGGER before recreating it, which leaves an interval — short, but real — in which an append-only table would accept an UPDATE. MariaDB replaces the trigger in one statement, so the guarantee never lapses.

MariaDB 11.4 specifics#

Decision	Why
`VARCHAR(n)` with a mandatory length	InnoDB cannot index an unbounded column, and every identifier column in this schema is a key or part of one.
`JSON`	In MariaDB this is an alias for `LONGTEXT`, not a distinct binary type as in MySQL. The spelling is kept because it documents intent and because `json_valid()` and the `JSON_*` functions work against it; nothing here relies on binary storage, since the canonical bytes are regenerated from the parsed object rather than read back from the column.
`DATETIME(6)` for derived instants	Microseconds is MariaDB's maximum. openEHR permits finer fractional seconds in the lexical form — which is why that form is stored separately and authoritatively.
`TINYINT(1)` for booleans	MariaDB has no boolean type; this is the conventional spelling and what every driver maps to `bool`.
`SIGNAL SQLSTATE '45000'` in append-only triggers	The documented way for a trigger to refuse, and what a driver surfaces as an error. Without it the guarantee would hold in application code only — and a guarantee a SQL console can walk around is not one.

Every instant is stored twice, and that is the point#

openEHR times are ISO 8601 strings with deliberate partial precision: 2024-05 is a date known to the month, and it is not 2024-05-01. A native timestamp column silently completes it — fabricating a clinical fact — and normalises the lexical form, breaking round-trip fidelity.

So each time occupies …_text (authoritative, exact) and …_utc (derived, nullable, for ordering). The derived column is NULL whenever the instant is not established, which is the same answer the library gives, so SQL and Rust cannot disagree about one record.

Testing#

cargo test

The tests are golden: they assert the SQL this crate emits, including assertions that it is not another engine's SQL, and that the two differences from MySQL above are actually present.

What is not here#

Not here	Why
A `Store`	This crate is a dialect. Level Schema means the schema is emitted and the engine has executed it, not that this crate can talk to a database.
A driver dependency	A dependency implies a capability, and readers reasonably infer one (`W16.4`).
Archetype or template validation	Not implemented anywhere in this project (`lib:S1.4`).
AQL execution	Parsed and statically checked by `openehr`, never executed (`S1.6`).

Fuzzing#

Identifier quoting is fuzzed by openehr-mariadb-fuzz, because an identifier that escapes its own delimiter is SQL injection and archetype ids reach a WHERE clause from caller input. Run in CI on every push.

Specification#

This crate implements the shared persistence specification; it defines nothing of its own beyond its dialect.

spec/databases/ — the storage model, the dialect boundary, the conformance ladder
spec/databases/conformance-matrix.md — what is verified for this engine today
spec/audit.md — known gaps

Licence#

Any of these, at your option — MIT, Apache-2.0, BSD-3-Clause, GPL-2.0-only, or GPL-3.0-only. See LICENSE.md.