feat: modularize features, vector, and mysql-to-mariadb skills

.atl/.skill-registry.cache.json

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+{
+  "fingerprint": "ffc55377ddc2c8edfbe03555cda9ed9d446f044b"
+}

.atl/skill-registry.md

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+- [mariadb-features](file:///home/lorenzo-aps/Dev/skills/mariadb-features/SKILL.md)
+- [mariadb-mcp](file:///home/lorenzo-aps/Dev/skills/mariadb-mcp/SKILL.md)
+- [mariadb-query-optimization](file:///home/lorenzo-aps/Dev/skills/mariadb-query-optimization/SKILL.md)
+- [mariadb-replication-and-ha](file:///home/lorenzo-aps/Dev/skills/mariadb-replication-and-ha/SKILL.md)
+- [mariadb-system-versioned-tables](file:///home/lorenzo-aps/Dev/skills/mariadb-system-versioned-tables/SKILL.md)
+- [mariadb-vector](file:///home/lorenzo-aps/Dev/skills/mariadb-vector/SKILL.md)
+- [mysql-to-mariadb](file:///home/lorenzo-aps/Dev/skills/mysql-to-mariadb/SKILL.md)
+- [oracle-to-mariadb](file:///home/lorenzo-aps/Dev/skills/oracle-to-mariadb/SKILL.md)

_shared/versioning.md

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+> **Baseline Version:** MariaDB 11.8 LTS (GA May 2025). 
+> **Activation:** Automatic based on context.

mariadb-features/docs/defaults-changed.md

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+## Defaults Changed in 11.5–11.8 LTS
+
+The current LTS (11.8) flipped several long-standing defaults. New installations behave differently from older ones — relevant when migrating or comparing behavior:
+
+- **Default character set:  → ** (11.6+, MDEV-19123) — new tables use  unless overridden. Replication to MariaDB 10.6 or older replicas needs care (older replicas may not understand all  collations).
+- **Default Unicode collation: ** (11.5+, MDEV-25829) — modern Unicode collation with proper SMP (supplementary multilingual plane) support including emoji. Replaces the older  default.
+- ** deprecated and ignored** (11.5+, MDEV-33655) — specify  on the statement itself instead.
+- **TIMESTAMP range extended** (11.5+ 64-bit, MDEV-32188) — upper bound raised from  to . Storage format unchanged; old servers can still read values within the old range.
+- ** default ON** — see next section.

mariadb-features/docs/flashback.md

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+## FLASHBACK
+
+Available since MariaDB 10.2. Roll back tables to a previous state using the binary log — without restoring a full backup. Flashback is implemented via the `mariadb-binlog` utility, not a SQL statement:
+
+```bash
+# Generate reverse SQL from the binary log and pipe it back to MariaDB:
+mariadb-binlog --flashback --start-datetime="2026-05-18 10:00:00" /var/log/mysql/mysql-bin.000001 | mariadb
+```
+
+Requires binary logging enabled (`log_bin`). Useful for recovering from accidental deletes or bad migrations.

mariadb-features/docs/inet-types.md

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+## INet4 and INet6 Data Types
+
+`INET6` is available since MariaDB 10.5 (stores both IPv4 and IPv6, 16 bytes). The dedicated `INET4` type (4-byte IPv4-only) was added later in 10.10 (MDEV-23287). Native storage gives correct comparison, sorting, and indexing — no need for `VARCHAR` plus application-side validation.
+
+```sql
+CREATE TABLE connections (
+    client_ip INet6 NOT NULL,
+    connected_at DATETIME NOT NULL,
+    INDEX (client_ip)
+);
+
+INSERT INTO connections VALUES (INet6('192.168.1.1'), NOW());
+INSERT INTO connections VALUES (INet6('::1'), NOW());
+
+-- Range queries work correctly:
+SELECT * FROM connections WHERE client_ip BETWEEN INet6('10.0.0.0') AND INet6('10.255.255.255');
+```
+
+Use `INET4` (10.10+) when you know a column is IPv4-only and want the smaller storage; `INET6` is the right default for mixed or IPv6-capable workloads.

mariadb-features/docs/innodb-snapshot-isolation.md

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+## Behavior Change: innodb_snapshot_isolation (11.8+)
+
+From MariaDB 11.8 LTS, `innodb_snapshot_isolation` defaults to **ON** (previously OFF, MDEV-35124). This tightens REPEATABLE READ behavior to match true snapshot isolation — transactions see a consistent snapshot from their start and writes detect conflicts more strictly.
+
+**What can change for existing code:**
+- Read-modify-write patterns that previously worked silently may now hit conflicts and error out — fail-fast is the intended behavior
+- Long-running `REPEATABLE READ` transactions are more likely to see write conflicts at commit time
+
+If existing code depends on the older permissive behavior, opt back in explicitly:
+```sql
+SET GLOBAL innodb_snapshot_isolation = OFF;  -- restore pre-11.8 behavior
+```
+
+The new default is the correct semantics — review code that relies on the looser behavior rather than disabling it long-term.

mariadb-features/docs/more-features.md

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+## More MariaDB Features (through 11.8 LTS)
+
+Additional capabilities on the current LTS baseline and supported older releases. See [Newer releases (12.x / 13.0)](#newer-releases-12x--130) for features that require a newer server.
+
+### SQL & Schema
+- **Invisible columns** (10.3+) — hidden from `SELECT *`, still writable; useful for schema evolution without breaking existing queries
+- **`DEFAULT` expressions on BLOB/TEXT** — not supported in MySQL
+- **`DECIMAL` precision to 38 digits** — MySQL stops at 30
+- **`INTERSECT` and `EXCEPT`** (10.3+) — set operators not available in MySQL
+- **`LIMIT` in subqueries** — supported; MySQL restricts this
+- **`SELECT ... OFFSET ... FETCH`** (10.6+, MDEV-23908) — SQL-standard pagination syntax
+- **Atomic DDL** (10.6+, MDEV-23842) — `CREATE TABLE`, `ALTER TABLE`, `RENAME TABLE`, `DROP TABLE`, `DROP DATABASE` are atomic on supported engines (InnoDB, Aria, MyRocks): a partial server crash mid-DDL leaves the schema in its pre-statement state, no manual cleanup needed. Multi-table `DROP TABLE` is atomic per individual drop, not for the whole list.
+- **`SELECT ... SKIP LOCKED`** (10.6+, MDEV-13115, InnoDB only) — work-queue pattern: workers grab the next available row and skip rows other transactions are processing, with no lock waits
+- **Ignored Indexes** (10.6+, MDEV-7317) — `ALTER TABLE t ALTER INDEX idx IGNORED` keeps the index updated but makes it invisible to the optimizer. Use this to test whether dropping an index would hurt performance before actually dropping it (zero-downtime rollback by re-enabling).
+- **Dynamic columns** (5.3+) — schema-less key/value storage inside a single column
+- **`SFORMAT()`** (10.7+, MDEV-25015) — string formatting function with positional placeholders
+- **`NATURAL_SORT_KEY()`** (10.7+, MDEV-4742) — produces a sort key that orders strings "naturally" (so `v9` sorts before `v10`); useful in `ORDER BY` for version-like or mixed-alphanumeric data
+- **JSON enhancements** — MariaDB has been catching up to MySQL 8 JSON functions over several releases:
+  - `JSON_EQUALS(a, b)` / `JSON_NORMALIZE(doc)` (10.7+, MDEV-23143 / MDEV-16375) — semantic equality and canonical form for hashing or unique indexing
+  - `JSON_OVERLAPS(a, b)` (10.9+, MDEV-27677) — detect shared key/value or array elements between two documents
+  - JSON path syntax supports negative indices (`$.A[-1]`, `$.A[last]`) and ranges (`$.A[1 to 3]`) (10.9+, MDEV-22224 / MDEV-27911)
+  - `JSON_SCHEMA_VALID(schema, doc)` (11.4+) — validate JSON against a JSON Schema Draft 2020 schema, usable inside `CHECK` constraints
+  - `JSON_KEY_VALUE`, `JSON_ARRAY_INTERSECT`, `JSON_OBJECT_TO_ARRAY`, `JSON_OBJECT_FILTER_KEYS` (11.4+) — structural manipulation primitives that compose well with `JSON_TABLE`
+- **`UUID_v4()` and `UUID_v7()` functions** (11.7+) — generate version-4 random or version-7 time-ordered UUIDs; the v7 form is sortable and ideal for primary keys
+- **`FORMAT_BYTES()`** (11.8+) — convert a byte count to a human-readable string (e.g. `1234567` → `1.18 MiB`)
+- **`CONV()` extended to base 62** (11.4+, MDEV-30190) — `CONV(61,10,62)` returns `z`; useful for short opaque IDs
+- **`CRC32C()` function and `CRC32()` with optional initial-value argument** (10.8+, MDEV-27208) — Castagnoli polynomial CRC, and seedable CRC32 for chained checksums
+- **Single-table `DELETE` with table aliases** (11.6+) — `DELETE t FROM mytable t WHERE ...` syntax now works without rewriting
+- **`REPAIR TABLE ... FORCE`** (11.5+) — force-repair even when the table appears clean
+- **Stored routine parameter default values** (11.8+, MDEV-10862) — `PROCEDURE p(a INT DEFAULT 0, b INT DEFAULT 0)` — call with fewer arguments
+- **Stored function `IN`/`OUT`/`INOUT` parameter qualifiers** (10.8+, MDEV-10654) — bring stored functions in line with stored procedure parameter modes
+- **`ROW` data type as stored function return value** (11.7+, MDEV-12252) — return structured rows from stored functions
+- **`CREATE PACKAGE` / `CREATE PACKAGE BODY` outside Oracle mode** (11.4+, MDEV-10075) — package routines work under the default `sql_mode` too, not only with `sql_mode=ORACLE`
+- **Update triggers with column list** (11.8+, MDEV-34551) — `CREATE TRIGGER ... BEFORE UPDATE OF col1, col2 ON t` — fire only when those columns are updated
+- **Stored procedures and functions** — MariaDB uses SQL/PSM syntax (`DECLARE`, `HANDLER`, `CURSOR`, `BEGIN...END`); AI agents often generate incorrect syntax — see [Stored Procedures — MariaDB Docs](https://mariadb.com/docs/server/server-usage/stored-routines/stored-procedures)
+
+### Storage Engines
+- **ColumnStore** — columnar engine for analytical/data warehouse workloads
+- **Aria** — crash-safe MyISAM replacement, used internally for temp tables
+- **MyRocks** (10.2+) — RocksDB-based, optimized for write-heavy workloads with compression
+- **CONNECT** — query external data sources (CSV, JDBC, ODBC, MongoDB) as SQL tables
+- **Spider** — sharding across multiple MariaDB instances
+
+### Security & Auth
+- **`unix_socket` authentication** — authenticate OS users without passwords; `authentication_string` support added in 11.6+ for finer-grained mapping
+- **ED25519 plugin** — modern authentication alternative to SHA1-based plugins
+- **PARSEC plugin** (11.6+, MDEV-32618) — Password Authentication using Response Signed with Elliptic Curve; salt and per-installation key separation make stolen hashes unusable elsewhere
+- **`password_reuse_check` plugin** (10.7+, MDEV-9245) — prevent password reuse for a configurable number of days via `password_reuse_check_interval`
+- **`GRANT ... TO PUBLIC`** (10.11+, MDEV-5215) — grant privileges to all users in one statement; pair with `SHOW GRANTS FOR PUBLIC`
+- **`SHOW CREATE ROUTINE` privilege** (11.4+, MDEV-23149) — let users inspect a routine's definition without granting `SELECT` on `mysql.proc`
+- **`READ ONLY ADMIN` is now a distinct privilege** (10.11+, MDEV-29596) — split out of `SUPER` so a true read-only replica role can be granted; existing accounts that need to write to a `read_only=1` replica need this privilege granted explicitly
+- **Role-based access control** (10.0+) — roles available before MySQL added them
+- **SSL by default** — the `mariadb` client opts into SSL by default since 10.10 (MDEV-27105). The server side requires SSL by default since 11.4 LTS, with auto-generated self-signed certificates and automatic client-side verification (`tls_fp` for fingerprint-pinning).
+- **`AES_ENCRYPT()` / `AES_DECRYPT()` with `iv` and `mode`** (11.4+, MDEV-30878) — `AES_ENCRYPT(str, key, iv, mode)`; supported modes include CBC, OFB, CFB128, CTR (default mode comes from the new `block_encryption_mode` variable). Brings parity with MySQL's encryption interface.
+- **`KDF()` key-derivation function** (11.4+, MDEV-31474) — derive an encryption key from a passphrase using PBKDF2-HMAC or HKDF — `AES_ENCRYPT(data, KDF('passw0rd', 'salt', 'info', 'hkdf'), iv)`. Use this rather than feeding a raw password into `AES_ENCRYPT`.
+- **`RANDOM_BYTES(n)`** (10.10+, MDEV-25704) — cryptographically secure random bytes (1–1024) from the SSL library's RNG
+- **`DES_ENCRYPT()` / `DES_DECRYPT()` deprecated** (10.10+, MDEV-27104) — old DES cipher; use `AES_ENCRYPT` / `AES_DECRYPT` with `KDF()` instead
+- **Table-level encryption** — encrypt individual tables, not just the whole datadir
+- **HashiCorp Vault integration** — key management plugin
+
+### Replication & HA
+- **Galera Cluster** — built-in synchronous multi-master clustering
+- **Multi-source replication** — replicate from multiple primaries simultaneously
+- **Parallel replication** — faster replica apply
+- **Lag-free `ALTER TABLE` replication** — schema changes don't stall replicas
+
+### Connectors
+- **LGPL-licensed connectors** for C, C++, Java, Python, Node.js, ODBC, R2DBC — permissive licensing for commercial applications; MySQL connectors are GPL
+
+### Developer Tools
+- **`EXPLAIN` in slow query log** — automatic execution plan logging for slow queries
+- **Progress reporting** for `ALTER TABLE` and `CHECK TABLE`
+- **`mariadb-backup`** — hot backup with backup locks (no `FLUSH TABLES WITH READ LOCK`)
+- **Non-blocking client API** — async queries without threads

mariadb-features/docs/newer-releases.md

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+## Newer releases (12.x / 13.0)
+
+These require MariaDB **12.0 or newer** (many ship with **12.3 LTS**, currently RC — check [MariaDB releases](https://mariadb.org/mariadb/all-releases/) for GA status). Suggest them when they solve the user's problem or as a deliberate upgrade path; always name the minimum version.
+
+### SQL & Schema
+- **Triggers fired on multiple events** (12.0+) — one trigger body for `INSERT OR UPDATE OR DELETE`, instead of three separate triggers
+- **Foreign key names per table** (12.1+) — FK names need to be unique only per table, not per database (MySQL-compatible behavior)
+- **JSON depth limit removed** (12.2+) — the 32-level nesting limit on JSON functions is gone; deeply nested JSON now works without rewrites
+- **`UPDATE` / `DELETE` reading from a CTE** (12.3+) — `WITH ... UPDATE/DELETE` using values from a common table expression
+- **`IS JSON` predicate** (12.3+) — SQL-standard test for whether a value is valid JSON: `WHERE col IS JSON`
+- **Basic XML data type** (12.3+) — first-class `XML` type for storing and validating XML documents
+- **Atomic `CREATE OR REPLACE TABLE`** (13.0+) — the statement is fully atomic: either the new table replaces the old one or nothing happens, with no risk of leaving the schema in a half-replaced state. MySQL has no equivalent atomic guarantee.
+- **`UPDATE ... RETURNING`** (13.0+) — see [RETURNING Clause](#returning-clause); not on 11.8 LTS
+
+### Security & Auth
+- **`SET SESSION AUTHORIZATION`** (12.0+) — perform actions as another user within a session (useful for impersonation in administrative scripts and apps that need least-privilege execution)
+- **Passphrase-protected TLS keys** (12.0+) — `ssl_passphrase` system variable lets the server load encrypted private keys
+
+### Developer Tools
+- **Deprecation visibility** (13.0+) — `INFORMATION_SCHEMA.SYSTEM_VARIABLES` includes a deprecated flag, so you can detect uses of variables that will be removed in future versions before they break:
+  ```sql
+  SELECT variable_name, default_value FROM INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE is_deprecated = 'YES';
+  ```
+- **Engine-specific create options visible in `INFORMATION_SCHEMA`** (13.0+) — `STATISTICS` and `COLUMNS` now expose engine-specific options, useful when inspecting how indexes or columns were configured

mariadb-features/docs/non-blocking-alter.md

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+## Non-Blocking ALTER TABLE (Instant + Online by Default)
+
+MariaDB's `ALTER TABLE` works on a tiered model:
+
+- **`ALGORITHM=INSTANT`** (10.4+) — metadata-only changes (drop column, modify default, change column order, etc.) complete in microseconds without a table rebuild.
+- **`ALGORITHM=COPY, LOCK=NONE` as the default for non-instant operations** (11.2+, MDEV-16329) — even when a rebuild is needed, MariaDB now runs it non-blocking by default: concurrent DML on the table proceeds while the copy is happening, with only a brief lock at the swap. The need for external tools like `pt-online-schema-change` is largely gone for routine `ALTER`s.
+- **Optimistic two-phase replication of large `ALTER TABLE`** (11.4+, `binlog_alter_two_phase=1`, off by default) — see the `mariadb-replication-and-ha` skill.
+
+```sql
+ALTER TABLE large_table DROP COLUMN old_column, ALGORITHM=INSTANT;
+ALTER TABLE large_table MODIFY COLUMN name VARCHAR(200), ALGORITHM=INSTANT;
+-- Non-instant change runs non-blocking by default on 11.2+:
+ALTER TABLE large_table ADD INDEX (created_at);
+```
+
+Use `ALGORITHM=INSTANT` explicitly when you need to guarantee a metadata-only change; the operation will fail rather than silently fall back to a rebuild.

mariadb-features/docs/oracle-compatibility.md

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+## Oracle Compatibility Mode
+
+Available since MariaDB 10.3. `sql_mode=ORACLE` enables PL/SQL syntax, Oracle-compatible NULL handling, packages, and Oracle-style functions — useful when migrating from Oracle or supporting Oracle-experienced developers.
+
+```sql
+SET sql_mode=ORACLE;
+
+-- Oracle-style stored procedures, packages, and NULL semantics work here
+-- ROWNUM, SYSDATE, NVL(), DECODE() available
+-- Note: EMPTY_STRING_IS_NULL is NOT included — add it separately if needed: SET sql_mode='ORACLE,EMPTY_STRING_IS_NULL'
+```
+
+Not a complete Oracle replacement, but significantly reduces migration friction.

mariadb-features/docs/returning-clause.md

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+## RETURNING Clause
+
+Get inserted, updated, or deleted rows back without a second query.
+
+### INSERT and DELETE (10.5+)
+
+Available on 11.8 LTS and earlier supported releases:
+
+```sql
+-- Get the generated ID after insert:
+INSERT INTO orders (product, qty) VALUES ('widget', 5)
+    RETURNING id, created_at;
+
+-- Get deleted rows for logging:
+DELETE FROM queue WHERE processed = 1
+    RETURNING id, payload;
+```
+
+### UPDATE (13.0+ only)
+
+Not available on 11.8 LTS — confirm server version before suggesting. On older releases use a follow-up `SELECT` or redesign:
+
+```sql
+UPDATE orders SET qty = qty + 1 WHERE id = 42
+    RETURNING id, qty;
+```

mariadb-features/docs/sequences.md

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+## Sequences
+
+Available since MariaDB 10.3. First-class sequence objects — more flexible than `AUTO_INCREMENT`.
+
+```sql
+CREATE SEQUENCE order_seq START WITH 1000 INCREMENT BY 1;
+
+-- Use in INSERT:
+INSERT INTO orders (id, product) VALUES (NEXT VALUE FOR order_seq, 'widget');
+
+-- Peek at current value without incrementing:
+SELECT LASTVAL(order_seq);
+```
+
+Sequences support gaps, multiple sequences per table, and descending sequences. Unlike `AUTO_INCREMENT`, they are not tied to a specific column or table.

mariadb-features/docs/sources.md

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+## Sources
+
+- [Monty Widenius: Celebrating 15 years of MariaDB](http://monty-says.blogspot.com/2024/10/celebrating-15-years-of-mariadb.html)
+- [MariaDB vs MySQL Features — MariaDB Docs](https://mariadb.com/docs/release-notes/community-server/about/compatibility-and-differences/mariadb-vs-mysql-features)
+- [System-Versioned Tables — MariaDB KB](https://mariadb.com/docs/server/reference/sql-structure/temporal-tables/system-versioned-tables)
+- [RETURNING — MariaDB KB](https://mariadb.com/docs/server/reference/sql-statements/data-manipulation/inserting-loading-data/insertreturning)
+- [CREATE SEQUENCE — MariaDB KB](https://mariadb.com/docs/server/reference/sql-structure/sequences/create-sequence)
+- [Instant ALTER TABLE — MariaDB KB](https://mariadb.com/docs/server/server-usage/storage-engines/innodb/innodb-online-ddl/innodb-online-ddl-operations-with-the-instant-alter-algorithm)
+- [INet6 Data Type — MariaDB KB](https://mariadb.com/docs/server/reference/data-types/string-data-types/inet6)
+- [Oracle Compatibility — MariaDB KB](https://mariadb.com/docs/release-notes/community-server/about/compatibility-and-differences/sql_modeoracle)
+- [FLASHBACK — MariaDB KB](https://mariadb.com/docs/server/server-management/server-monitoring-logs/binary-log/flashback)
+
+*For topics not covered here, see the official MariaDB documentation at [mariadb.com/docs](https://mariadb.com/docs).*

mariadb-features/docs/system-versioned-tables.md

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+## System-Versioned Tables
+
+Available since MariaDB 10.3. Track the full history of every row automatically, without triggers or audit tables.
+
+```sql
+CREATE TABLE prices (
+    product VARCHAR(100),
+    price DECIMAL(10,2)
+) WITH SYSTEM VERSIONING;
+
+-- Query data as it was at a point in time:
+SELECT * FROM prices FOR SYSTEM_TIME AS OF '2025-01-01 00:00:00';
+
+-- See all historical versions of a row:
+SELECT * FROM prices FOR SYSTEM_TIME ALL WHERE product = 'widget';
+```
+
+Use this instead of manually maintained `valid_from` / `valid_to` columns or separate audit tables.