Request for firstRow/allRows convenience methods

[aloisbarreras]

When executing queries with this library like so:
db.query('select * from users').then(res => res.rows[0]);

I very often just want to get the first row from the result, and it's tedious to retype the .then(res => res.rows[0]) every time.

It would be great to add some convenience methods like firstRow() or allRows() that would save a lot of typing. For example:

db.query('select * from users').firstRow()
db.query('select * from users').allRows()
db.query('select * from users')

Omitting the methods would maintain the current functionality.

Let me know if you think this is a worthwhile addition.

[charmander]

query returns a promise, so you could include those on the configurable promise implementation for pools:

class QueryPromise extends Promise {
    firstRow() {
        return this.then(result => result.rows[0]);
    }

    allRows() {
        return this.then(result => result.rows);
    }
}

const db = new pg.Pool({
    …,
    Promise: QueryPromise,
});

#1518 adds the same functionality to clients.