database

The database worker connects to PostgreSQL, MySQL, and SQLite through a managed per-database connection pool. Every callable surface lives under the database::* namespace. The driver is chosen from each database URL scheme (sqlite:, postgres://, postgresql://, mysql://).

Runtime settings live in the configuration worker under id database; pools hot-reload when the value changes. SQLite is the recommended starting point. Placeholder syntax: ? for SQLite and MySQL, $1/$2/… for Postgres.

When to Use

• You need to read rows from a configured database (database::query).
• You need to insert, update, delete, or run DDL and read affected-row counts or autoincrement ids (database::execute).
• Several statements must commit or roll back together as one unit (database::transaction, database::executeBatch, or the interactive transaction surface).
• The same parameterized SQL will run many times and you want to skip per-call parse/plan cost (database::prepareStatement + database::runStatement).
• You need read-your-writes across round-trips with logic between steps (database::beginTransaction … commitTransaction / rollbackTransaction).

Boundaries

• Not a migration tool, ORM, or schema designer — pass raw SQL only.
• Not a general pub/sub bus. database::row-changed reports only what THIS worker wrote, on commit — not change data capture; a write from psql or another worker is invisible to it.
• database::query is read-oriented; use database::execute for writes. Running a SELECT through execute discards rows.
• Prepared handles pin a pool connection until TTL expiry — not transactions. Batch database::transaction / database::executeBatch need every statement up front; use the interactive surface when code must branch between steps.
• MySQL ignores the returning option on execute (warn-once). SQLite degrades read_committed / repeatable_read isolation to serializable.
• For filesystem or shell operations, use the shell worker instead.

Functions

• database::query — run read-only SQL and return rows, row count, and column metadata.
• database::execute — run write SQL (INSERT/UPDATE/DELETE/DDL) and return affected rows, optional last insert id, and optional RETURNING rows.
• database::executeBatch — convenience form of transaction: statements may be bare SQL strings or {sql, params} objects (prefer params for dynamic values). Same atomic semantics, envelope, and failed_index reporting as transaction.
• database::prepareStatement — parse and plan SQL once; return a handle that pins a pool connection until TTL expiry.
• database::runStatement — re-execute a prepared handle with new bind params; response shape matches query.
• database::transaction — run an ordered batch of statements atomically; rolls back on first failure and reports failed_index.
• database::beginTransaction — open an interactive transaction and return an id plus expiry deadline.
• database::transactionQuery — read SQL inside an open interactive transaction; same envelope as query.
• database::transactionExecute — write SQL inside an open interactive transaction; same envelope as execute. Rejects bare transaction-control SQL — finalize via commitTransaction or rollbackTransaction.
• database::commitTransaction — commit and finalize an interactive transaction.
• database::rollbackTransaction — roll back and finalize an interactive transaction.
• database::listDatabases — every configured database with its driver, credential-redacted URL, pool settings and TLS mode. Config only; use database::health for live state.

Interactive transactions auto-roll back when timeout_ms elapses (default 30 s, max 5 min). Prepared handles default to a 1 h TTL (max 24 h) with no explicit release call — let them expire or stop using them when done.

Reading the schema

One shape across all three drivers — prefer these over hand-writing sqlite_master / information_schema / PRAGMA.

• database::listTables — tables and views, with kind and (postgres) schema.
• database::describeTable — columns with type, nullability, default, primary key and a structured foreign_key of { schema, table, column }; plus indexes and a planner row estimate.
• database::describeSchema — the same for every table in one pass. Use this rather than looping describeTable.
• database::schemaDiagram — positioned nodes, routed foreign-key edges, hub degree and isolated tables. For reasoning about a schema's shape, not only for drawing it.

Reading data

• database::browseTable — paged, sorted, filtered reads with no SQL. Filters are { column, op, value } and total honours them. Follow a foreign key with an equality filter at page_size: 1.
• database::explain — the plan as a tree with costs and warnings. analyze runs the statement, so it defaults to false and is refused for anything that is not a single read.
• database::columnStats — planner statistics by default (approximate, labelled source: planner); exact: true scans. To profile rows you already hold, use the fp worker on a browseTable result instead.

Operations and reuse

• database::health — pool occupancy, active queries, table sizes, locks, cache ratio. Each section is available, unsupported or denied, so a driver gap is never mistaken for an empty result.
• database::terminateQuery — end a session, or cancel its statement with cancel_only. Takes an id from database::health.
• database::saveQuery, database::listSavedQueries, database::deleteSavedQuery — named queries per database, kept in the state worker.
• database::history — recent queries, newest first. Best effort, not an audit log; bind database::row-changed for that.

Reacting to writes

Register a database::row-changed trigger to be told when this worker commits a change, instead of polling:

{ "trigger_type": "database::row-changed", "config": { "db": "primary", "table": "orders", "ops": ["insert"] } }

The event is { db, table, op, affected_rows, returning?, at }. It fires on commit — an interactive transaction's writes are announced by commitTransaction, and a rollback announces nothing. table is null when the statement's table cannot be read off the SQL (a CTE-wrapped write), and runStatement does not fire because it has no affected-row count to report. Delivery is best-effort: it is not durable with the commit and has no replay or exactly-once guarantee.