@dortdb/datetime

A date and time extension for DortDB, a modular framework for querying JavaScript data structures. It is also a worked example of how a DortDB extension packages extra functions.

Installation

npm install @dortdb/core @dortdb/datetime

@dortdb/core is a peer dependency.

Functions

Every language in the engine can call these functions.

• now() returns the current timestamp as a JavaScript Date.
• interval(string) parses an interval string and returns an Interval. It accepts SQL-standard syntax such as '1-2 3 4:5:6' and PostgreSQL syntax such as '1 year 2 months ago'.
• date.add(Date | Interval, Interval) adds an interval to a date and returns a Date, or sums two intervals component-wise and returns an Interval.
• date.sub(Date | Interval, Interval) is the same in reverse. It subtracts an interval from a date, or one interval from another.
• date.extract(Date, string) returns one field of a date. The field is year, month, day, hour, minute, or second. month is 1-based. Any other field name throws.

date.add and date.sub correct for daylight saving time when the date is at midnight and the interval is a whole number of days, so adding '1 day' never shifts the clock time.

The package also exports the Interval type.

Usage

Pass the extension to the DortDB constructor. This example pairs it with SQL.

import { DortDB } from '@dortdb/core';
import { datetime } from '@dortdb/datetime';
import { defaultRules } from '@dortdb/core/optimizer';
import { SQL } from '@dortdb/lang-sql';

const db = new DortDB({
  mainLang: SQL(),
  optimizer: { rules: defaultRules },
  extensions: [datetime],
});

const result = db.query(`
  SELECT date.extract(date.sub(now(), interval('3 years')), 'year') AS y
`);
// result.data -> [{ y: <the current year minus 3> }]

Documentation

See Functions & Aggregates for how extensions work and how to write your own, or the full docs at filipjezek.github.io/dortdb.