feat(statement_timeout): Support for PostgreSQL statement_timeout

docs/usage.md

@@ -213,6 +213,10 @@ const sequelize = new Sequelize('database', 'username', 'password', {
 })
 ```
 
+If you're using pg@^7.3.0, you can optionally provide a `statement_timeout` value in milliseconds in your `dialect` settings. 
+If provided, PostgreSQL will cancel any query after it exceeds your `statement_timeout` value. This is useful for running on systems
+like Heroku where queries cannot exceed the maximum HTTP timeout of 30 seconds.
+
 ### MSSQL
 
 The library for MSSQL is`tedious@^1.7.0` You'll just need to define the dialect:

lib/dialects/postgres/connection-manager.js

@@ -79,7 +79,10 @@ class ConnectionManager extends AbstractConnectionManager {
           'binary',
           // This should help with backends incorrectly considering idle clients to be dead and prematurely disconnecting them.
           // this feature has been added in pg module v6.0.0, check pg/CHANGELOG.md
-          'keepAlive'
+          'keepAlive',
+          // Abort any statement that takes more than the specified number of milliseconds, starting from the time the command arrives at the server from the client.
+          // see also [https://www.postgresql.org/docs/9.6/static/runtime-config-client.html]
+          'statement_timeout'
         ]));
     }
 
@@ -155,7 +158,7 @@ class ConnectionManager extends AbstractConnectionManager {
 
       return new Promise((resolve, reject) => connection.query(query, (error, result) => error ? reject(error) : resolve(result))).then(results => {
         const result = Array.isArray(results) ? results.pop() : results;
-        
+
         for (const row of result.rows) {
           let type;
           if (row.typname === 'geometry') {

test/integration/dialects/postgres/connection-manager.test.js

@@ -3,11 +3,11 @@
 const chai = require('chai'),
   expect = chai.expect,
   Support = require(__dirname + '/../../support'),
-  dialect = Support.getTestDialect(),
   DataTypes = require(__dirname + '/../../../../lib/data-types'),
+  dialect = Support.getTestDialect(),
   _ = require('lodash');
 
-if (dialect.match(/^postgres/)) {
+if ( dialect.match(/^postgres/) ) {
   describe('[POSTGRES] Sequelize', () => {
     function checkTimezoneParsing(baseOptions) {
       const options = _.extend({}, baseOptions, { timezone: 'Asia/Kolkata', timestamps: true });
@@ -31,5 +31,38 @@ if (dialect.match(/^postgres/)) {
       DataTypes.HSTORE.types.postgres.array_oids = [];
       return checkTimezoneParsing(this.sequelize.options);
     });
+
+    if ( process.env.DIALECT === 'postgres' ) {
+
+      // This test will only run with node-pg 7.3.0 or greater. node-pg requires node-pg-native 2.0.0 or greater.
+      // node-pg-native 2.0.0 breaks a bunch of tests.
+      it.skip('should properly pass statement_timeout to postgres', function() {
+        const options = _.extend({}, this.sequelize.options, { dialectOptions: { 'statement_timeout': 10 } });
+        const sequelize = Support.createSequelizeInstance(options);
+
+        return sequelize.query('SHOW statement_timeout')
+          .then( result => {
+            const timeout = _.get( result, '[0].statement_timeout' );
+            expect(timeout).to.equal('10ms');
+          });
+      });
+
+      // This test will only run with node-pg 7.3.0 or greater. node-pg requires node-pg-native 2.0.0 or greater.
+      // node-pg-native 2.0.0 breaks a bunch of tests.
+      it.skip('should properly error when a statement is cancelled due to a statement_timeout', function() {
+        const self = this;
+        const options = _.extend({}, this.sequelize.options, { dialectOptions: { 'statement_timeout': 10 } });
+        const sequelize = Support.createSequelizeInstance(options);
+
+        return sequelize.query('SELECT pg_sleep(1)')
+          .then( () => {
+            expect.fail('Postgres should have cancelled the query with an error');
+          })
+          .catch( self.sequelize.DatabaseError, error => {
+            expect(error.parent.code).to.equal('57014'); // postgres query_cancelled error
+          });
+      });
+    }
+
   });
 }