hdb - Pure JavaScript SAP HANA Database Client

Table of contents

• Install
• SAP Support for hdb and @sap/hana-client
• Getting started
• Establish a database connection
• Direct Statement Execution
• Prepared Statement Execution
• Bulk Insert
• Streaming results
• Transaction handling
• Streaming Large Objects
• CESU-8 encoding support
• TCP Keepalive
• Setting Session-Specific Client Information
• Running tests
• Running examples

Install

Install from npm:

npm install hdb

or clone from the GitHub repository to run tests and examples locally:

git clone https://github.com/SAP/node-hdb.git
cd node-hdb
npm install

SAP Support for hdb and @sap/hana-client

The hdb and @sap/hana-client Node.js SAP HANA client drivers are supported by SAP for connecting to SAP HANA Cloud and SAP HANA Platform servers. When starting a new project, it is encouraged to use the fully featured @sap/hana-client driver (documentation).

npm install @sap/hana-client

Below is a major feature comparison chart between the two drivers:

The hdb driver may also have different APIs or lack support for SAP HANA server features where the @sap/hana-client is fully supported. APIs that are the same in both drivers may have different behaviour.

Getting started

If you do not have access to an SAP HANA server, go to the SAP HANA Developer Center and choose one of the options to use SAP HANA Express or deploy a new SAP HANA Cloud server.

This is a very simple example showing how to use this module:

var hdb    = require('hdb');
var client = hdb.createClient({
  host     : 'hostname',
  port     : 30015,
  user     : 'user',
  password : 'secret'
});
client.on('error', function (err) {
  console.error('Network connection error', err);
});
client.connect(function (err) {
  if (err) {
  	return console.error('Connect error', err);
  }
  client.exec('select * from DUMMY', function (err, rows) {
	client.end();
    if (err) {
      return console.error('Execute error:', err);
    }
    console.log('Results:', rows);
  });
});

Establish a database connection

The first step to establish a database connection is to create a client object. It is recommended to pass all required connect options like host, port, user and password to the createClient function. They will be used as defaults for any following connect calls on the created client instance. Options beginning with the prefix "SESSIONVARIABLE:" are used to set session-specific client information at connect time (see example of setting EXAMPLEKEY=EXAMPLEVALUE below). In case of network connection errors like a connection timeout or a database restart, you should register an error event handler in order to be able to handle these kinds of problems. If there are no error event handlers, errors will not be emitted.

var hdb    = require('hdb');
var client = hdb.createClient({
  host     : 'hostname',
  port     : 30015,
  user     : 'user',
  password : 'secret',
  'SESSIONVARIABLE:EXAMPLEKEY' : 'EXAMPLEVALUE'
});
client.on('error', function (err) {
  console.error('Network connection error', err);
});
console.log(client.readyState); // new

When a client instance is created it does not immediately open a network connection to the database host. Initially, the client is in a 'new' state. When you call connect for the first time, two things are done internally:

1. A network connection is established and the communication is initialized (Protocol - and Product Version exchange). Now the connection is ready for exchanging messages but no user session is established as the client is in a disconnected state. This step is skipped if the client is already in a disconnected state.

2. The authentication process is initiated. After a successful user authentication a database session is established and the client is in a connected state. If authentication fails the client remains in a 'disconnect' state.

client.connect(function (err) {
  if (err) {
    return console.error('Error:', err);
  }
  console.log(client.readyState); // connected
});

If user and password are specified they will override the defaults of the client. It is possible to disconnect and reconnect with a different user on the same client instance and the same network connection.

The client also supports SAP HANA systems installed in multiple-container (MDC) mode. In this case a single SAP HANA system may contain several isolated tenant databases. A database is identified by its name. One of the databases in an MDC setup is the system database which is used for central system administration. One can connect to a specific tenant database directly via its host and SQL port (as shown in the example above) or via the system database which may lookup the exact host and port of a particular database by a given name.

var hdb    = require('hdb');
var client = hdb.createClient({
  host         : 'hostname', // system database host
  port         : 30013,      // system database port
  databaseName : 'DB1',      // name of a particular tenant database
  user         : 'user',     // user for the tenant database
  password     : 'secret'    // password for the user specified
});

The client also accepts an instance number instead of the port of the system database:

var hdb    = require('hdb');
var client = hdb.createClient({
  host           : 'hostname', // system database host
  instanceNumber : '00',       // instance number of the HANA system
  databaseName   : 'DB1',      // name of a particular tenant database
  user           : 'user',     // user for the tenant database
  password       : 'secret'    // password for the user specified
});

Multiple hosts can be provided to the client as well:

var hdb    = require('hdb');
var client = hdb.createClient({
  hosts : [ { host: 'host1', port: 30015 }, { host: 'host2', port: 30015 } ],
  user     : 'user',
  password : 'secret'
});

This is suitable for multiple-host SAP HANA systems which are distributed over several hosts. The client establishes a connection to the first available host from the list.

Authentication mechanisms

Details about the different authentication methods can be found in the SAP HANA Security Guide.

User / Password

Users authenticate themselves with their database user and password.

SAML assertion

SAML bearer assertions as well as unsolicited SAML responses that include an unencrypted SAML assertion can be used to authenticate users. SAML assertions and responses must be signed using XML signatures. XML Digital signatures can be created with xml-crypto or xml-dsig.

Instead of user and password you have to provide a SAML assertion:

client.connect({
  assertion: '<Assertion xmlns="urn:oasis:names:tc:SAML:2.0:assertion" ...>...</Assertion>'
},function (err) {
  if (err) {
    return console.error('Error:', err);
  }
  console.log('User:', client.get('user'));
  console.log('SessionCookie:', client.get('SessionCookie'));
});

After a successful SAML authentication, the server returns the database user and a SessionCookie which can be used for reconnecting.

JWT token

JWT tokens can also be used to authenticate users.

Instead of user and password you have to provide a JWT token:

client.connect({
  token: 'eyJhbGciOiJSUzI1NiJ9....'
},function (err) {
  if (err) {
    return console.error('Error:', err);
  }
  console.log('User:', client.get('user'));
  console.log('SessionCookie:', client.get('SessionCookie'));
});

After a successful JWT authentication, the server returns the database user and a SessionCookie which can be used for reconnecting.

Encrypted network communication

To establish an encrypted database connection just pass either key, cert and ca or a pfx to createClient.

var client = hdb.createClient({
  host : 'hostname',
  port : 30015,
  key  : fs.readFileSync('client-key.pem'),
  cert : fs.readFileSync('client-cert.pem'),
  ca   : [fs.readFileSync('trusted-cert.pem')],
  ...
});

Use the useTLS option if you would like to connect to SAP HANA using Node.js's trusted certificates.

var client = hdb.createClient({
  host : 'hostname',
  port : 30015,
  useTLS: true,
  ...
});

Note for MDC use cases: The system database and the target tenant database may be configured to work with different certificates. If so, make sure to include all the necessary TLS-related properties for both the databases in the client's options.

In case you need custom logic to validate the server's hostname against the certificate, you can assign a callback function to the checkServerIdentity property, alongside the other connection options. The callback is supplied to the tls.connect funciton of the TLS API and should conform to the signature described there.

Direct Statement Execution

Direct statement execution is the simplest way to execute SQL statements. The only input parameter is the SQL command to be executed. Generally, statement execution results are returned using callbacks. The type of returned result depends on the kind of statement.

DDL Statement

In the case of a DDL statement nothing is returned:

client.exec('create table TEST.NUMBERS (a int, b varchar(16))', function (err) {
  if (err) {
    return console.error('Error:', err);
  }
  console.log('Table TEST.NUMBERS has been created');
});

DML Statement

In the case of a DML Statement the number of affectedRows is returned:

client.exec('insert into TEST.NUMBERS values (1, \'one\')', function (err, affectedRows) {
  if (err) {
    return console.error('Error:', err);
  }
  console.log('Number of affected rows:', affectedRows);
});

Query

The exec function is a convenient way to completely retrieve the result of a query. In this case all selected rows are fetched and returned in the callback. The resultSet is automatically closed and all Lobs are completely read and returned as buffer objects. If streaming of the results is required you will have to use the execute function. This is described in section Streaming results:

client.exec('select A, B from TEST.NUMBERS order by A', function(err, rows) {
  if (err) {
    return console.error('Error:', err);
  }
  console.log('Rows:', rows);
});

Different Representations of Query Results

The default representation of a single row is an object where the property names are the columnDisplayNames of the resultSetMetadata:

var command = 'select top 1 * from t1';
client.exec(command, function(err, rows) {
  /* rows will be an array like this:
  [{
    ID: 1,
    A: 't1.1.a',
    B: 't1.1.b'
  }]
  */
});

If your SQL statement is a join with overlapping column names, you may want to get separate objects for each table per row. This is possible if you set option nestTables to TRUE:

var command = 'select top 1 * from t1 join t2 on t1.id = t2.id';
var options = {
  nestTables: true
};
client.exec(command, options, function(err, rows) {
  /* rows will be an array like this now:
  [{
    T1: {
      ID: 1,
      A: 't1.1.a',
      B: 't1.1.b',
    },
    T2: {
      ID: 1
      A: 't2.1.a',
      B: 't2.1.b',
    },
  }]
  */
});

It is also possible to return all rows as an array where the order of the column values is exactly the same as in the resultSetMetadata. In this case you have to set the option rowsAsArray to TRUE:

var command = 'select top 1 * from t1 join t2 on t1.id = t2.id';
var options = {
  rowsAsArray: true
};
client.exec(command, options, function(err, rows) {
  /* rows will be an array like this now:
  [[
    1,
    't1.1.a',
    't1.1.b',
    1
    't2.1.a',
    't2.1.b'
  ]]
  */
});

Prepared Statement Execution

Prepare a Statement

The client returns a statement object which can be executed multiple times:

client.prepare('select * from DUMMY where DUMMY = ?', function (err, statement){
  if (err) {
    return console.error('Error:', err);
  }
  // do something with the statement
  console.log('StatementId', statement.id);
});

Execute a Statement

The execution of a prepared statement is similar to the direct statement execution on the client. The difference is that the first parameter of the exec function is an array with positional parameters. In case of named parameters it can also be an parameters object:

statement.exec(['X'], function (err, rows) {
  if (err) {
    return console.error('Error:', err);
  }
  console.log('Rows:', rows);
});

If you use the execute function instead of the exec function the resultSet is returned in the callback like in the direct query execution above.

Calling Stored Procedures

If you have a stored procedure similar to the following example:

create procedure PROC_DUMMY (in a int, in b int, out c int, out d DUMMY, out e TABLES)
  language sqlscript
  reads sql data as
  begin
    c := :a + :b;
    d = select * from DUMMY;
    e = select * from TABLES;
  end

You can call it via a prepared statement. The second argument is always an object with the scalar parameters. If there are no scalar parameters, an empty object {} is returned. The following arguments are the resultSets:

client.prepare('call PROC_DUMMY (?, ?, ?, ?, ?)', function(err, statement){
  if (err) {
    return console.error('Prepare error:', err);
  }
  statement.exec({
    A: 3,
    B: 4
  }, function(err, parameters, dummyRows, tableRows) {
    if (err) {
      return console.error('Exec error:', err);
    }
    console.log('Parameters:', parameters);
    console.log('Dummies:', dummyRows);
    console.log('Tables:', tableRows);
  });
});

Note: Default values for stored procedures are not supported.

Drop Statement

To drop the statement simply call:

statement.drop(function(err){
  if (err) {
    return console.error('Drop error:', err);
  }
  console.log('Statement dropped');
});

The callback is optional in this case.

Using Datetime types

If you want to use DATETIME types in a prepared statement, be aware that strings like '14.04.2016 12:41:11.215' are not processed by the SAP HANA Database but by the node-hdb module. Therefore, you must use the exact required format that would be returned by a selection made with this module. The formats are:

TIME: '13:32:20'
DATE: '2016-04-14'
TIMESTAMP: '2016-04-14T13:32:20.737'
SECONDDATE: '2016-04-14T13:32:20'

Another possibility is to use the functions TO_DATE, TO_DATS, TO_TIME and TO_TIMESTAMP in your SQL statement to convert your string to a valid DATETIME type.

Bulk Insert

If you want to insert multiple rows with a single execution you just have to provide the all parameters as array, for example:

client.prepare('insert into TEST.NUMBERS values (?, ?)', function(err, statement){
  if (err) {
    return console.error('Prepare error:', err);
  }
  statement.exec([[1, 'one'], ['2', 'two'], [3, 'three']], function(err, affectedRows) {
    if (err) {
      return console.error('Exec error:', err);
    }
    console.log('Array of affected rows:', affectedRows);
  });
});

For further details, see: app9.

Streaming results

If you use the execute function of the client or statement instead of the exec function, a resultSet object is returned in the callback instead of an array of all rows. The resultSet object allows you to create an object based row stream or an array based stream of rows which can be piped to an writer object. Don't forget to close the resultSet if you use the execute function:

client.execute('select A, B from TEST.NUMBERS order by A', function(err, rs) {
  if (err) {
    return console.error('Error:', err);
  }
  rs.setFetchSize(2048);
  rs.createObjectStream()
    .pipe(new MyWriteStream())
    .on('finish', function (){
      if (!rs.closed) {
       rs.close();
      }
    });
});

For further details, see app4.

Transaction handling

The default behavior is that each statement is automatically committed. If you want to manually control commit and rollback of a transaction, you can do this by calling setAutoCommit(false) on the client object:

function execTransaction(cb) {
  client.setAutoCommit(false);
  async.series([
    client.exec.bind(client, "insert into NUMBERS values (1, 'one')"),
    client.exec.bind(client, "insert into NUMBERS values (2, 'two')")
  ], function (err) {
    if (err) {
      client.rollback(function(err){
        if (err) {
          err.code = 'EROLLBACK';
          return cb(err);
        }
        cb(null, false);
      });
    } else {
      client.commit(function(commitError){
        if (err) {
          err.code = 'ECOMMIT';
          return cb(err);
        }
        cb(null, true);
      });
    }
    client.setAutoCommit(true);
  });
}

execTransaction(function(err, ok){
  if (err) {
    return console.error('Commit or Rollback error', err);
  }
  if (ok) {
    console.log('Commited');
  } else {
    console.log('Rolled back');
  }
})

For further details, see: tx1.

Streaming Large Objects

Read Streams

Reading large object as stream can be done if you use the execute method of client or statement. In this case for all LOB columns a Lob object is returned. You can call createReadStream or read in order create a readable stream or to read the LOB completely.

Write Streams

Writing large objects is automatically done. You just have to pass a Readable instance or a buffer object as parameter.

For further details, see: app7.

CESU-8 encoding support

The SAP HANA server connectivity protocol uses CESU-8 encoding. Node.js does not suport CESU-8 natively and the driver by default converts all text to CESU-8 format in the javascript layer including SQL statements.

Due to the fact that Node.js has built-in support for UTF-8, using UTF-8 in the HDB drivers can lead to performance gains especially for large text data. If you are sure that your data contains only BMP characters, you can disable CESU-8 conversion by setting a flag in the client configuration.

createClient accepts the parameter useCesu8 to disable CESU-8 support. Here is how to provide the configuration:

var hdb    = require('hdb');
var client = hdb.createClient({
  host     : 'hostname',
  port     : 30015,
  user     : 'user',
  password : 'secret',
  useCesu8 : false
});

This setting is per client and cannot be changed later.

Note: Using CESU-8 brings performance penalties proportionate to the text size that has to be converted.

TCP Keepalive

To configure TCP keepalive behaviour, include the tcpKeepAliveIdle connect option. The value provided for this option is the number of seconds before an idle connection will begin sending keepalive packets. By default, TCP keepalive will be turned on with a value of 200 seconds. If a value of 0 is specified, keepalive behaviour is determined by the operating system. The following example creates a client whose connections will begin sending keepalive packets after 300 seconds.

var hdb    = require('hdb');
var client = hdb.createClient({
  host             : 'hostname',
  port             : 30015,
  user             : 'user',
  password         : 'secret',
  tcpKeepAliveIdle : 300
});

TCP keepalive can be explicity disabled by specifying tcpKeepAliveIdle=false as in the example below.

var hdb    = require('hdb');
var client = hdb.createClient({
  host             : 'hostname',
  port             : 30015,
  user             : 'user',
  password         : 'secret',
  tcpKeepAliveIdle : false
});

Setting Session-Specific Client Information

The client information is a list of session variables (defined in property-value pairs that are case sensitive) that an application can set on a client object. These variables can be set at connection time via "SESSIONVARIABLE:" prefixed options, or by using the setClientInfo method to specify a single property-value pair.

var hdb    = require('hdb');
var client = hdb.createClient({
  host             : 'hostname',
  port             : 30015,
  user             : 'user',
  password         : 'secret',
  "SESSIONVARIABLE:EXAMPLEKEY1" : "EXAMPLEVALUE1"
});
client.setClientInfo("EXAMPLEKEY2", "EXAMPLEVALUE2");

Session variables set via the setClientInfo method will be sent to the server during the next execute, prepare, or fetch operation.

Running tests

To run the unit tests for hdb simply run:

make test-unit

To run the unit tests as well as acceptance tests for hdb you have to run:

make test

For the acceptance tests a database connection has to be established. Therefore, you need to copy the configuration template config.tpl.json in the test/db folder to config.json and change the connection data to yours. If the config.json file does not exist a local mock server is started.

Running examples

For any examples you need a valid config.json in the test/db folder.

• app1: Simple query.
• app2: Fetch rows from ResultSet.
• app3: Streaming rows createObjectStream().
• app4: Pipe row into JSON-Transform and to stdout.
• app5: Stream from the filesystem into a db table.
• app6: Stream from a db table into the filesystem.
• app7: Insert a row with a large image into a db table (uses WriteLobRequest and Transaction internally).
• app8: Automatic reconnect when network connection is lost.
• app9: Insert multiple rows with large images into a db table as one batch.
• app10: Usage example of query option nestTables.
• call1: Call stored procedure.
• call2: Call stored procedure with lob input and output parameter.
• call3: Call stored procedure with table as input parameter.
• tx1: Transaction handling (shows how to use commit and rollback).
• csv: Stream a db table into csv file.
• server: Stream rows into http response http://localhost:1337/{schema}/{tablename}?top={top}

To run the first example:

node examples/app1

Licensing

Copyright 2013-2021 SAP SE or an SAP affiliate company and node-hdb contributors. Please see our LICENSE for copyright and license information. Detailed information including third-party components and their licensing/copyright information is available via the REUSE tool.