Query result

Query result size

Query result size can be set with the Connection option replySize. It defines the number of data rows returned in the initial response. By default, this option is set to -1, which means fetching all the data. If replySize is set to a positive number, only that many data rows will be fetched, while the rest will stay cached at the server. The replySize can be set when connection is created or by invoking the setReplySize method on the Connection object.

// set replySize to 100
const conn = new Connection({database: 'test', replySize: 100});
await conn.connect();
let res = await conn.execute("select * from generate_series(1, 1001)");
console.log(res.data.length);
// 100
await conn.setReplySize(-1); // back to default
res = await conn.execute("select * from generate_series(1, 1001)");
console.log(res.data.length);
// 1000

Streaming query result

When the query result is large, it's often useful to start processing the data chunks as soon as they are available on the client. This can be achieved by invoking the execute method on the Connection object with stream=true.

import { Connection } from 'monetdb'
 
const conn = new Connection({database: 'test'})
const ready = await conn.connect();
const stream = await conn.execute('select * from generate_series(1, 10000)', true);
const colInfo = [];
const data = [];
stream.on('header', (cols) => {
    console.log(cols);
});
 
stream.on('data', (tuples) => {
    for (let t of tuples) {
        data.push(t);
    }
});
 
stream.on('end', () => {
    console.log(data);
    console.log('THE END')
    conn.close();
});
File TransferPrepare Statement