@dortdb/lang-xquery

An XQuery language plug-in for DortDB. It adds XQuery, the language for tree-shaped and XML-like data: DOM documents, parsed XML, and similar hierarchical structures, with XPath path navigation and FLWOR transformations.

Installation

npm install @dortdb/core @dortdb/lang-xquery

@dortdb/core is a peer dependency.

Usage

import { DortDB } from '@dortdb/core';
import { defaultRules } from '@dortdb/core/optimizer';
import { XQuery, DomDataAdapter } from '@dortdb/lang-xquery';

const db = new DortDB({
  // in a browser, XQuery() picks up the global document automatically
  mainLang: XQuery({ adapter: new DomDataAdapter(document) }),
  optimizer: { rules: defaultRules },
});

const people = new DOMParser().parseFromString(
  `<people>
     <person age="30">Alice</person>
     <person age="20">Bob</person>
   </people>`,
  'text/xml',
);
db.registerSource(['people'], people);

db.query('for $p in $people/people/person[@age > 25] return string($p)');
// ['Alice']

Data adapter

The default adapter targets DOM and XML trees, and also reads JS object properties through the attribute axis (obj/@prop). In the browser the global document is used automatically; in Node.js supply a document from a DOM implementation (such as jsdom) and make the DOM globals available, or provide a custom adapter for your own tree shape.

Dialect

This is a subset of XQuery 3.0 focused on data selection: path expressions, FLWOR, and sequence operations. It deliberately omits the type system, so the following are not available and are not planned: the as keyword, typeswitch, instance of, treat, castable, validate, function types other than function(*), and named function references with arity (fnname#arity). Only cast expressions are supported.

Not implemented today, but possibly added later: try / catch, pragma expressions, the window FLWOR clause, inline functions, %private / %public annotations, and module prolog features beyond namespace definitions.

Custom plan operators

XQuery extends the DortDB unified algebra with two operators:

| Operator | Description | | ---------------- | ------------------------------------------------------------------------------------------------------------------------------------------------ | | ProjectionSize | Adds an attribute holding the total number of rows in the stream (exposes $fs:last during path navigation). | | TreeJoin | Implements path steps like a/b/c. Like ProjectionConcat, but its expression yields items, and it also supplies the XQuery focus per step ($fs:dot, $fs:position, $fs:last). |

These demonstrate that the algebra is extensible; see Extending DortDB.

Documentation

See the XQuery overview and dialect reference, or the full docs at filipjezek.github.io/dortdb.