f884891862
- db-postgres.md: PG17 patterns (indexes, pooling, backup); [E4] - db-sqlite.md: WAL prod patterns, Turso/LiteFS/D1, FTS5 - db-sqlx.md: Rust compile-time checked queries, offline mode - db-drizzle.md: TS schema-first, drizzle-kit migrations - db-migration-hygiene.md: universal up/down, zero-downtime, backfill, checksum tracking All blocks <60 LOC per Constructor Pattern. Version numbers marked [UNVERIFIED] where exact minor pins are needed. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
34 lines
2.2 KiB
Markdown
34 lines
2.2 KiB
Markdown
# DB — SQLite (prod-suitable) patterns
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Use when the workload is read-heavy, single-writer-acceptable, or needs zero-ops embedded storage. SQLite is prod-suitable — Fly.io, Turso, Cloudflare D1, and countless CLI/mobile apps run it in production. [E4 — expert assessment]
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**When NOT to use:** high-concurrency write workload (> ~1 writer/sec sustained), multi-region strong consistency, horizontal write scaling. Use Postgres instead.
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**WAL mode is mandatory for prod:**
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```sql
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PRAGMA journal_mode = WAL; -- readers don't block writer, writer doesn't block readers
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PRAGMA synchronous = NORMAL; -- durable across app crash, NOT across power loss (use FULL if PSU-risk)
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PRAGMA busy_timeout = 5000; -- 5s wait for lock instead of instant SQLITE_BUSY
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PRAGMA foreign_keys = ON; -- default OFF in SQLite (!), always enable
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PRAGMA temp_store = MEMORY;
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```
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Apply these on every connection open — they are per-connection, not per-database (except `journal_mode` which persists).
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**Distributed patterns:**
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- **Turso** (libSQL fork): edge-replicated read replicas with HTTP/WebSocket wire protocol. Primary single-writer, replicas read-only. [E4]
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- **LiteFS** (Fly.io): file-system replication, leader-election via Consul. Primary+replicas. [E4]
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- **Cloudflare D1**: managed SQLite on edge with their own replication. [UNVERIFIED: current throughput limits]
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- **Litestream**: continuous replication to S3/R2 for backup + PITR; single node, not HA.
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**Full-text search (FTS5):**
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```sql
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CREATE VIRTUAL TABLE docs_fts USING fts5(title, body, content=docs, content_rowid=id);
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CREATE TRIGGER docs_ai AFTER INSERT ON docs BEGIN
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INSERT INTO docs_fts(rowid, title, body) VALUES (new.id, new.title, new.body);
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END;
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```
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FTS5 outperforms bolt-on `LIKE '%x%'` by 100×+ on large text corpora. Native, no extension install.
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**Backup:** `sqlite3 db '.backup /path/backup.db'` while app runs (safe with WAL). Or Litestream for continuous.
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**Forbidden:** multiple writer processes without a coordination layer; opening the same DB over NFS (lock semantics broken); `DELETE FROM bigtable` without `VACUUM` after (doesn't shrink file); committing the `.db` / `.db-wal` / `.db-shm` files to git.
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