#3_query_statistics.js

/**
 * Run query on BigQuery and print query statistics
 * @param {string} query The query to run
 * @param {string} location The location of the dataset
 * @returns {Promise<void>}
 */
const runQueryWithStatistics = async (query, location) => {
    const options = {
        query,
        // Location must match that of the dataset(s) referenced in the query.
        location,
        // Normally this should be kept to 'true' but we set it to false 
        // to be able to measure everything correctly
        useQueryCache: false,
    };

    // Run the query as a job
    let [job] = await bigquery.createQueryJob(options);

    // Wait for the query to finish
    await job.getQueryResults();

    // Getting fresh job data and print them
    [job] = await job.get();
    printJobStatistics(job);
}

/**
 * Takes a BigQuery job and print certain statistical values to the console
 * @param {Job} job The BigQuery job to analyze
 */
const printJobStatistics = (job) => {
    const statistics = job.metadata.statistics;
    const timeTaken = statistics.endTime - statistics.startTime;
    const totalBytesProcessed = parseInt(statistics.totalBytesProcessed);
    const totalBytesBilled = parseInt(statistics.query.totalBytesBilled);
    const totalPartitionsProcessed = parseInt(statistics.query.totalPartitionsProcessed);

    const rowsRead = parseInt(statistics.query.queryPlan[0].recordsRead);

    console.log(`--- Job Statistics ---`);
    console.table([
        { Description: 'Cache hit', Value: statistics.query.cacheHit, Unit: 'Bool' },
        { Description: 'Time taken', Value: timeTaken, Unit: 'ms' },
        { Description: 'Partitions processed', Value: totalPartitionsProcessed, Unit: 'Count' },
        { Description: 'Rows read', Value: rowsRead, Unit: 'Count' },
        { Description: 'Bytes processed', Value: totalBytesProcessed, Unit: 'Bytes' },
        { Description: 'Bytes billed', Value: totalBytesBilled, Unit: 'Bytes' },
    ]);
    console.log(`-------------------------------\n`);
}

const main = async () => {
    
    // TODO: Developer, make sure to add your GCP project ID here!
    const projectId = 'my_project';
    // TODO: Developer, make sure to add your dataset ID here!
    const datasetId = 'my_dataset';
    const location = 'US';

    const createQuery = (tableId) => `
        SELECT * 
        FROM \`${projectId}.${datasetId}.${tableId}\`
        WHERE date = Date("2021-01-03")
        LIMIT 10
    `;

    console.log(`--- Without Partition ---`);
    await runQueryWithStatistics(
        createQuery('non_partitioned_table'),
        location
    );

    console.log(`--- With Partition ---`);
    await runQueryWithStatistics(
        createQuery('partitioned_table'),
        location
    );

}
main();