Building SQL QueriesDocumentation

MySQL Connection Options

  • connectionString (string | false, default: process.env.DATABASE_URL)

  • bigIntMode ('string' | 'number' | 'bigint', default: 'number') - This option specifies how BigInts should be returned from MySQL. All types are supported when writing to BigInt fields. 'string' and 'bigint' both support any value that can be contained in a MySQL BigInt field. 'number' is simpler to use, but will result in inaccurate values for very large numbers (greater than Number.MAX_SAFE_INTEGER). 'bigint's cannot be passed to JSON.stringify.

  • poolSize (number, default: 10) - the maximum number of connections in the connection pool

  • maxUses (number, default: Infinity) - the maximum number of times a connection can be returned from the connection pool before being closed and replaced with a fresh connection

  • idleTimeoutMilliseconds (number, default: 30_000ms) - max milliseconds a client can go unused before it is removed from the pool and destroyed

  • queueTimeoutMilliseconds (number, default: 60_000ms) - number of milliseconds to wait for a connection from the connection pool before throwing a timeout error

  • acquireLockTimeoutMilliseconds (number, default: 60_000ms) - Number of milliseconds to wait for a lock on a connection/transaction. This is helpful for catching cases where you have accidentally attempted to query a connection within a transaction that is on that connection, or attempted to query an outer transaction within a nested transaction

Event Handlers

For more detail on how to use event handlers, see Logging & Debugging - install @databases/pg and run your first query

  • onError(err: Error) - called for global connection errors. e.g. when MySQL terminates a connection that is not currently in use

  • onQueryStart(query: SQLQuery, formatted: {text: string, values: unknown[]}) - called before executing a query

  • onQueryResults(query: SQLQuery, formatted: {text: string, values: unknown[]}, results: unknown[]) - called after a query succeeds

  • onQueryError(query: SQLQuery, formatted: {text: string, values: unknown[]}, err: Error) - called when a query results in an Error

  • onConnectionOpened() - called after a new connection is openned in the pool

  • onConnectionClosed() - called after a connection is closed in the pool

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