Allow client instance instead of configuration

docs/configuration.md

@@ -2,24 +2,26 @@
 
 ### connectionConfig
 
-- Type: `object`
+- Type: `object | Client`
 - Default: `null`
 - Required: `true`
 
-Connection configuration object for [node-postgres](https://node-postgres.com/features/connecting#programmatic)
+Connection configuration object for [node-postgres](https://node-postgres.com/features/connecting#programmatic).
+
+It can be an existing `pg.Client` instance, too. In this case the instance already has to be connected.
 
 ### defaultSchema
 
 - Type: `string`
 - Default: `'public'`
 - Required: `false`
 
-It will be used in objects whose names do not contain a schema name
+It will be used in objects whose names do not contain a schema name.
 
 ### logging
 
 - Type: `boolean | function`
 - Default: `console.info`
 - Required: `false`
 
-Option to enable logging in the console or callback of the format `function(...messages) {}` for displaying a message about changes
+Option to enable logging in the console or callback of the format `function(...messages) {}` for displaying a message about changes.

lib/index.js

@@ -16,6 +16,8 @@ const errors = require('./errors');
 
 const Metalize = require('metalize');
 
+const { Client } = require('pg');
+
 const Logger = require('./logger');
 const ConnectionManager = require('./connection-manager');
 
@@ -194,11 +196,16 @@ class Differ {
 
     let error;
     let preparedChanges;
+    let client;
 
     this._logger.info(chalk.green('Sync started'));
 
-    const client = ConnectionManager.getClient(this._connectionConfig);
-    await client.connect();
+    if (this._connectionConfig instanceof Client) {
+      client = this._connectionConfig;
+    } else {
+      client = ConnectionManager.getClient(this._connectionConfig);
+      await client.connect();
+    }
 
     try {
       await client.query('set search_path to public');
@@ -220,7 +227,9 @@ class Differ {
       error = e;
     }
 
-    await client.end();
+    if (!(this._connectionConfig instanceof Client)) {
+      await client.end();
+    }
 
     if (error) throw error;
 

types/index.d.ts

@@ -5,6 +5,8 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+import { Client } from 'pg';
+
 interface ReferenceOptions {
   table: string;
   columns: string[];
@@ -127,7 +129,7 @@ interface ImportOptions {
 }
 
 interface DifferOptions {
-  connectionConfig: object;
+  connectionConfig: object | Client;
   defaultSchema?: string;
   logging?: boolean | Function;
 }