iterator() — drizzle-orm Function Reference

Architecture documentation for the iterator() function in session.ts from the drizzle-orm codebase.

Function typescript DrizzleORM DatabaseDrivers calls 2

Entity Profile

DrizzleORM→ DatabaseDrivers→ iterator() — drizzle-orm Function Reference

Dependency Diagram

graph TD
  2ee408d3_cd7c_fb7d_ddd5_fef534434ea7["iterator()"]
  070ed5d0_5637_0d4b_a489_d4cae342d1a6["MySql2PreparedQuery"]
  2ee408d3_cd7c_fb7d_ddd5_fef534434ea7 -->|defined in| 070ed5d0_5637_0d4b_a489_d4cae342d1a6
  de33a64d_c330_3f3d_0ac5_16396e49b35b["isPool()"]
  2ee408d3_cd7c_fb7d_ddd5_fef534434ea7 -->|calls| de33a64d_c330_3f3d_0ac5_16396e49b35b
  142c245f_17c2_a0a5_6518_2c3fc9552143["query()"]
  2ee408d3_cd7c_fb7d_ddd5_fef534434ea7 -->|calls| 142c245f_17c2_a0a5_6518_2c3fc9552143
  style 2ee408d3_cd7c_fb7d_ddd5_fef534434ea7 fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

drizzle-orm/src/mysql2/session.ts lines 145–195

	async *iterator(
		placeholderValues: Record<string, unknown> = {},
	): AsyncGenerator<T['execute'] extends any[] ? T['execute'][number] : T['execute']> {
		const params = fillPlaceholders(this.params, placeholderValues);
		const conn = ((isPool(this.client) ? await this.client.getConnection() : this.client) as {} as {
			connection: CallbackConnection;
		}).connection;

		const { fields, query, rawQuery, joinsNotNullableMap, client, customResultMapper } = this;
		const hasRowsMapper = Boolean(fields || customResultMapper);
		const driverQuery = hasRowsMapper ? conn.query(query, params) : conn.query(rawQuery, params);

		const stream = driverQuery.stream();

		function dataListener() {
			stream.pause();
		}

		stream.on('data', dataListener);

		try {
			const onEnd = once(stream, 'end');
			const onError = once(stream, 'error');

			while (true) {
				stream.resume();
				const row = await Promise.race([onEnd, onError, new Promise((resolve) => stream.once('data', resolve))]);
				if (row === undefined || (Array.isArray(row) && row.length === 0)) {
					break;
				} else if (row instanceof Error) { // eslint-disable-line no-instanceof/no-instanceof
					throw row;
				} else {
					if (hasRowsMapper) {
						if (customResultMapper) {
							const mappedRow = customResultMapper([row as unknown[]]);
							yield (Array.isArray(mappedRow) ? mappedRow[0] : mappedRow);
						} else {
							yield mapResultRow(fields!, row as unknown[], joinsNotNullableMap);
						}
					} else {
						yield row as T['execute'];
					}
				}
			}
		} finally {
			stream.off('data', dataListener);
			if (isPool(client)) {
				conn.end();
			}
		}
	}