MySQL Patterns

Constraints

• Apply @rules/sql/optimalize.mdc — it already owns indexing, SARGable WHERE, seek/keyset pagination, EXPLAIN, transactions/locking basics, batch-over-per-row, CTE/window/recursive queries, schema basics, DB-level caching, and the Performance Non-Regression on Query Changes gate. Do not re-explain those here; defer to it. When a pattern in this skill changes an existing query (e.g. swapping LIKE for a FULLTEXT match, moving a filter onto a generated column, introducing partition pruning), capture the original query's baseline and confirm the new shape is equal or faster — if it is slower, document the reason and the remaining optimization options per that gate.
• For diagnosing an existing slow query, use @skills/mysql-problem-solver/SKILL.md. This skill is for designing features, not investigating regressions.
• If the project uses Laravel, also apply @rules/laravel/laravel.mdc and @rules/laravel/architecture.mdc.
• Apply @rules/security/backend.md — parameterized queries / ORM only, least-privilege DB users, never hardcode credentials.
• final classes, declare(strict_types=1), Pest tests for any data-access code added.
• Verify the engine/version before using a version-specific feature (SELECT VERSION();). MySQL 8 and MariaDB diverge on JSON, ON DUPLICATE KEY aliases, and SKIP LOCKED.

Use when

• Adding upserts, JSON columns, full-text search, generated columns, or partitioning to a Laravel app.
• Setting up read/write splitting against replicas, or hardening against deadlocks and connection exhaustion.
• Reviewing a migration that introduces any of the above on a large table.

These topics complement the query-tuning rules; they are not covered there.

Upserts

Pick the narrowest tool. All run as single statements — never loop per row.

// Insert-or-update many rows in ONE statement.
// 2nd arg = unique-by columns; 3rd = columns to overwrite on conflict.
Product::upsert(
    [['sku' => 'A1', 'price' => 10], ['sku' => 'B2', 'price' => 20]],
    uniqueBy: ['sku'],
    update: ['price'],
);

// Insert, silently skip rows that violate a unique key. No update.
DB::table('tags')->insertOrIgnore([['name' => 'php'], ['name' => 'sql']]);

// Single row: fetch-or-create-then-update. Fires model events; runs SELECT + INSERT/UPDATE.
Product::updateOrCreate(['sku' => 'A1'], ['price' => 10]);

• upsert() / insertOrIgnore() are bulk and do not fire model events or touch timestamps automatically (set them yourself). Prefer them for large batches.
• updateOrCreate() is per-row, fires events, and is race-prone under concurrency unless a unique index backs the match columns. Wrap in a deadlock retry (below) when concurrent.
• Raw form: INSERT ... ON DUPLICATE KEY UPDATE price = VALUES(price) (MariaDB) / ... AS new ON DUPLICATE KEY UPDATE price = new.price (MySQL 8, VALUES() deprecated).
• A unique index on the conflict columns is mandatory or the upsert degrades to plain inserts.

JSON Columns + Indexes

JSON columns cannot be indexed directly. Index a generated column extracted from the JSON, or a multi-valued index for arrays.

Schema::table('products', function (Blueprint $table): void {
    $table->json('attributes');
    // Stored generated column promotes attributes->'$.color' to an indexable scalar.
    $table->string('color')->storedAs("attributes->>'$.color'");
    $table->index('color');
});

// Querying JSON paths in Eloquent:
Product::where('attributes->color', 'red')->get();
Product::whereJsonContains('attributes->tags', 'sale')->get();

• ->> (or JSON_UNQUOTE(JSON_EXTRACT(...))) returns the unquoted scalar; index that, not the raw ->.
• VIRTUAL columns compute on read (no storage, index still allowed); STORED persists (faster read, costs disk + write). Default to VIRTUAL unless the column is read-heavy.
• Validate JSON shape in the application; MySQL only enforces well-formedness, not structure.

Full-Text Search

For natural-language search on TEXT columns, a FULLTEXT index beats LIKE '%term%' (which is non-SARGable, see @rules/sql/optimalize.mdc).

Schema::table('articles', function (Blueprint $table): void {
    $table->fullText(['title', 'body']);
});

// Boolean mode supports +required -excluded "phrase" operators.
Article::whereFullText(['title', 'body'], 'laravel +redis', ['mode' => 'boolean'])->get();
// Or raw:
Article::whereRaw(
    'MATCH(title, body) AGAINST(? IN NATURAL LANGUAGE MODE)',
    ['laravel redis'],
)->get();

• Default innodb_ft_min_token_size is 3 — shorter terms are ignored unless you lower it and rebuild the index.
• FULLTEXT covers basic relevance ranking only. For typo tolerance, facets, or large corpora, reach for a dedicated engine (Meilisearch/Elasticsearch via Laravel Scout). Note the tradeoff; do not over-engineer for small tables.

Generated / Virtual Columns

Beyond JSON, generated columns normalize derived values so they stay consistent and become indexable.

$table->decimal('net', 15, 2);
$table->decimal('vat_rate', 5, 4);
$table->decimal('gross', 15, 2)->virtualAs('net * (1 + vat_rate)');

• A generated column cannot reference another generated column defined after it, nor non-deterministic functions (NOW(), RAND()).
• Use them to enforce an invariant in one place instead of recomputing it in every query.

Partitioning

Partitioning splits one logical table across physical segments to prune scans and cheapen bulk drops. Use it for genuinely large, time- or range-sliced tables — not by default.

-- RANGE: time-series; drop old data instantly with ALTER TABLE ... DROP PARTITION.
CREATE TABLE events (
    id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
    created_at DATETIME NOT NULL,
    PRIMARY KEY (id, created_at)         -- partition key MUST be in every unique key
) PARTITION BY RANGE (YEAR(created_at)) (
    PARTITION p2024 VALUES LESS THAN (2025),
    PARTITION p2025 VALUES LESS THAN (2026),
    PARTITION pmax  VALUES LESS THAN MAXVALUE
);

-- LIST: discrete buckets (e.g. region/tenant).
PARTITION BY LIST (region_id) (
    PARTITION eu VALUES IN (1, 2, 3),
    PARTITION us VALUES IN (4, 5)
);

• Every UNIQUE / PRIMARY key must include the partition column — this often forces a composite PK and reshapes the schema. Decide early.
• Partition pruning only triggers when the partition key appears in the WHERE; a query without it scans every partition.
• Laravel migrations have no partition DSL — use DB::statement(...) with raw SQL.

Replication & Read/Write Splitting

Route reads to replicas, writes to the primary, with a single connection config.

// config/database.php — 'mysql' connection
'read'  => ['host' => ['10.0.0.2', '10.0.0.3']],
'write' => ['host' => ['10.0.0.1']],
'sticky' => true,

• sticky => true routes reads back to the write host for the rest of the request after any write, so a just-written row is read back consistently despite replication lag. Keep it on for typical web flows.
• Force a specific connection when needed: Model::on('mysql::read') or DB::connection('mysql')->select(...).
• Replicas are eventually consistent. Never read a balance/counter you just wrote from a replica without sticky or an explicit write-connection read.

Deadlock Retry

InnoDB aborts one transaction in a deadlock (SQLSTATE 40001, error 1213). The correct response is to retry the whole transaction, not to catch-and-continue.

DB::transaction(function (): void {
    // ... ordered, consistent locking; lock rows in a stable order to reduce deadlocks
}, attempts: 3); // Laravel retries the closure on deadlock up to `attempts` times.

• Keep transactions short, lock rows in a consistent order across code paths, and touch the fewest rows possible.
• Idempotency matters: the closure runs up to N times, so it must be safe to re-run.
• See @rules/sql/optimalize.mdc for the transaction/locking fundamentals this builds on.

Connection Config & Timeouts

// config/database.php 'mysql' → 'options'
PDO::ATTR_TIMEOUT => 3,              // connect timeout (seconds)
PDO::ATTR_PERSISTENT => false,       // avoid stale persistent conns behind PgBouncer-style poolers

• Set wait_timeout / interactive_timeout server-side to reclaim idle connections; size max_connections to (workers + queue workers + scheduler) × pool.
• Enable the slow query log (slow_query_log = 1, long_query_time = 1) to surface candidates for @skills/mysql-problem-solver/SKILL.md.

Diagnostics Cheatsheet

SHOW ENGINE INNODB STATUS\G          -- LATEST DETECTED DEADLOCK + lock waits
SHOW FULL PROCESSLIST;               -- live queries, state, time, lock waits
SHOW INDEX FROM orders;              -- existing indexes (verify before adding one)
SELECT * FROM information_schema.innodb_trx;          -- open transactions
SELECT * FROM performance_schema.data_lock_waits;     -- who blocks whom (MySQL 8)
SELECT table_name, data_length, index_length
  FROM information_schema.tables WHERE table_schema = DATABASE();  -- sizes

Done when

• The chosen feature is verified against the actual engine/version.
• Any pattern that changed an existing query was benchmarked against its baseline and is equal or faster; a slower result carries the documented reason and remaining optimization options (@rules/sql/optimalize.mdc "Performance Non-Regression on Query Changes").
• Upserts run as single statements with a backing unique index; concurrent ones are deadlock-retried.
• JSON / FULLTEXT / partition queries are confirmed to hit the intended index (EXPLAIN — see @rules/sql/optimalize.mdc).
• Read/write splitting keeps sticky on for read-after-write paths.
• Pest tests cover the new data-access paths; no secrets are hardcoded.