Multiple connections

A laranex-schema document is multi-connection: connections holds every database connection the producer read, each with its own name, driver, default schema, coverage and tables, in any mix of PostgreSQL, MySQL, MariaDB and SQLite. A single-connection document is simply a document with one entry. See Connections and tables in the contract.

Read several databases into one document

introspectAll reads each connection in its own worker, which receives only its own URL, and merges the results into one strictly validated 2.0 document:

import { introspectAll, writeDocument } from 'node-schema-viewer';

const document = await introspectAll([
    { url: process.env.APP_DATABASE_URL!, connection: 'default' },
    { url: process.env.ANALYTICS_DATABASE_URL!, connection: 'analytics' },
    { url: 'sqlite:./data/local.db', connection: 'local' },
]);
writeDocument(document, 'schema-viewer.json');

Connection names must be distinct, and one failing connection fails the whole inspection; nothing falls back to partial or declared metadata. See database introspection.

Ids and names

Table ids are qualified by connection, ["<connection>", <schema or null>, "<table>"], so users in two connections are two tables. A foreign key never crosses connections, because a constraint lives in one database; an ORM relationship may.

In the viewer

By default every connection is laid out in its own labelled frame (name, driver, table count, diagnostics). Pick one in the header's connection menu, step through them with [ and ], or open #connection=<id>. With more than one connection, every table label names its connection. See the viewer guide and try the three-connection document in the live demo.

In MCP

The MCP tools address tables by their exact ids, which include the connection, and schema_compare takes scopes by connection name (CONNECTION or CONNECTION:SCHEMA). See MCP.

Comparing connections

A comparison scope is a connection, optionally with one of its schemas. Compare two connections, such as a primary and a replica or the same application on PostgreSQL and MySQL:

npx node-schema-viewer compare primary=replica
npx node-schema-viewer check primary=replica --severity error

See schema comparison.

Configuring connections for build

build configures each connection in package.json under databases.NAME, by the environment variable that holds its URL (urlEnv), never the URL itself, with its schemas, driver and schema modules; see build configuration.