@sap/hdbext

@sap/hdbext

This module provides convenient functions on top of the hdb module.

The change log describes notable changes in this package.

Usage

var hdbext = require('@sap/hdbext');

API

createConnection(hanaConfig, callback)

Creates a connection to a HANA database:

var hanaConfig = {
  host     : 'hostname',
  port     : 30015,
  user     : 'user',
  password : 'secret'
};
hdbext.createConnection(hanaConfig, function(error, client) {
  if (error) {
    return console.error(error);
  }

  client.exec(...);
});

The hanaConfig argument contains database connection options and additional options. The callback provides a connected client object (see hdb).

If the application will be deployed in Cloud Foundry or XSA, you can use @sap/xsenv package to lookup the bound HANA service, like this:

var xsenv = require('@sap/xsenv');

var hanaConfig = xsenv.cfServiceCredentials({ tag: 'hdb' });
hdbext.createConnection(hanaConfig, function(error, client) {
  //...
});

Database connection options

The HANA options provided to @sap/hdbext should be in the same format as expected by the hdb package.

For convenience these properties set by the HANA service broker in the SAP HANA XS Advanced platform are also accepted:

• db_hosts - can be used instead of the hosts property of the hdb driver.
• certificate - can be used instead of ca property of the hdb driver. Note: certificate is a string containing one certificate, while ca is an array of certificates.

Additional options

A connection created with @sap/hdbext can be further configured with the following options:

Option	Type	Description
schema	string	Used to set current schema.
autoCommit	boolean	Sets the autoCommit flag. If no option is specified it defaults to true
isolationLevel	enum	One of hdbext.constants.isolation values. Used to set transaction isolation level.
locale	string	Used to set connection locale.
session	object	Object with key/value pairs that will be set as session variables.

Special session variables

Some session variables are handled in a special way.

• XS_APPLICATIONUSER - can be set to a user token (SAML/JWT) to associate the aplication user with the database connection
• SAP_PASSPORT - used to propagate SAP passport to SAP HANA, used for end-to-end tracing
• APPLICATION - the name of the application initiating the database connection

Note: If providing an SAP Passport in the session object of the additional options, it should have already been updated with data, specific to the component that consumes @sap/hdbext. For more information, see the documentation of the @sap/e2e-trace package.

The Express middleware provided by this package sets automatically XS_APPLICATIONUSER and SAP_PASSPORT by extracting relevant data from the HTTP request (for requests that use client credentials token only the latter is set).

Example

Sample configuration with both database connection options and additional options:

{
  host: 'my.host',
  port: 30015,
  user: 'my_user',
  password: 'secret',
  schema: 'name_of_the_schema',
  isolationLevel: hdbext.constants.isolation.SERIALIZABLE,
  locale: 'en_US',
  session: {
    APPLICATION: 'myapp',
    SAP_PASSPORT: 'passport'
  }
}

connectionOptions.getGlobalOptions()

Provides default values for these connection options:

• session.APPLICATION - extracted from VCAP_APPLICATION
• session.APPLICATIONVERSION - extracted from package.json in current directory

The application can override these defaults by setting these options explicitly.

connectionOptions.getRequestOptions(req)

Provides these connection options based on the given HTTP request (req):

• session.SAP_PASSPORT (Updated with default component data)
• session.XS_APPLICATIONUSER (Only for requests that do not use client credentials token)
• locale

updateConnectionOptions(client, options, callback)

It is also possible to change options on existing connection by using the updateConnectionOptions function:

hdbext.updateConnectionOptions(client, options, function(error) {
  if (error) {
    return console.error(error);
  }

  // ...
});

options is an object having properties same as the additional options.

loadProcedure(client, schemaName, procedureName, callback)

Calling stored procedures could become complex using plain hdb driver, so there are functionalities provided to simplify these calls.

For example, if you have the following stored procedure:

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 the hdb driver in the following way:

client.prepare('call PROC_DUMMY (?, ?, ?, ?, ?)', function(err, statement) {
  if (err) {
    return console.error(err);
  }

  statement.exec({ A: 3, B: 4 }, function(err, parameters, dummyRows, tableRows) {
    if (err) {
      return console.error(err);
    }

    console.log('C:', parameters.C);
    console.log('Dummies:', dummyRows);
    console.log('Tables:', tableRows);
  });
});

Note: Non-quoted names are automatically converted to uppercase by HANA.

With @sap/hdbext you don't need to construct a CALL statement. The procedure can be loaded by its name. The code can look like this:

hdbext.loadProcedure(client, 'MY_SCHEMA', 'PROC_DUMMY', function(err, sp) {
  sp({ A: 3, B: 4 }, function(err, parameters, dummyRows, tableRows) {
    if (err) {
      return console.error(err);
    }

    console.log('C:', parameters.C);
    console.log('Dummies:', dummyRows);
    console.log('Tables:', tableRows);
  });
});

To use the current schema, pass an empty string '', null or undefined for schema.

loadProcedure(client, schemaName, procedureName, callback) retruns a JavaScript function which you can call directly. The function has the paramsMetadata property containing metadata for all parameters of the stored procedure. This could be useful if you need to implement generic stored procedures calling.

You can also pass the input parameters directly in the proper order:

sp(3, 4, function(err, parameters, dummyRows, tableRows) {
  // ...
});

or as an array:

sp([3, 4], function(err, parameters, dummyRows, tableRows) {
  // ...
});

Where the big advantage comes in, is with table parameters. You can pass an array of objects and @sap/hdbext will auto convert it into a table parameter. Say we have a customer table with ID and NAME columns and the following procedure:

create procedure "getCustomers" (in in_table_1 "customer")
language sqlscript reads sql data as begin
select * from :in_table_1;
end;

You can call it like this:

client.loadProcedure('MY_SCHEMA', 'getCustomers', function(err, sp) {
  if (err) {
    return console.error(err);
  }

  sp([
    { ID: 1, NAME: 'alex' },
    { ID: 2, NAME: 'peter' }
  ], function(err, parameters, dummyRows, tableRows) {
    // ...
  });
});

In this example each array element represents a table row. Property names should case-sensitively match the corresponding column names.

Internally @sap/hdbext creates a local temporary table in the current schema for each table parameter. Thus, the current user needs the respective permissions.

Input arguments for parameters that have default values can be skipped in order to use the defined defaults. It is recommended to pass the input as an object in those cases. In this way the application code would be independent from the order in which parameters with default values are defined in the procedure. When the parameters are passed in a sequence (i.e. as an array or are passed directly in the proper order), input arguments can be skipped only for the parameters which are after the last mandatory parameter in the procedure's list.

Connection Pooling

@sap/hdbext implements a simple generic-pool for pooling connections.

To use it you first synchronously create the pool:

var pool = hdbext.getPool(hanaConfig, poolConfig);

The hanaConfig argument contains both database connection options and additional options.

The poolConfig argument is optional. It may contain configurations for the pool itself.

You can acquire a client from the pool. It is delivered via a callback:

pool.acquire(function(err, client) {
  // ...
});

If settings of the pooled connection need to be changed, an optional options object can be used.

pool.acquire(options, function(err, client) {
  // ...
});

Refer to the additional options section for more details.

When the client is no longer needed you should release it to the pool with pool.release(client);, client.close(); or client.disconnect();.

When the pool is no longer needed you can dispose of the idle connections by draining the pool with pool.drain().

The following property can be used to access the actual pool (refer to the generic-pool module):

pool.pool

For managing your own pools, you can use:

var pool = hdbext.createPool(hanaConfig, poolConfig);

The options hanaConfig and poolConfig are same as above.

Express Middleware

@sap/hdbext provides an Express middleware which allows easy access to a connection pool in an Express based application. In the background a connection pool is created. The connection is automatically returned to the pool when the express request is closed or finished.

var hdbext = require('@sap/hdbext');
var express = require('express');

var app = express();
app.use(hdbext.middleware(hanaConfig, poolConfig));

app.get('/execute-query', function (req, res) {
  var client = req.db;

  client.exec('SELECT * FROM DUMMY', function (err, rs) {
    if (err) {
      return res.end('Error: ' + err.message);
    }

    res.end(JSON.stringify(rs));
  });
});

The argument hanaConfig may contain both database connection options and additional options.

The argument poolConfig is optional. It may contain configurations for the created pool.

The middleware sets the XS_APPLICATIONUSER and the SAP_PASSPORT session variables automatically, if the corresponding data is available in the HTTP request. For requests that use client credentials token only the latter is set. It also sets APPLICATION and APPLICATIONVERSION session variables automatically to some default values extracted from the environment.

SQL Parameter Utilities

The hdbext.sqlInjectionUtils object contains several synchronous utility functions that can be used to prevent SQL injections.

isAcceptableParameter(value, maxToken)

Returns true if value can be used to construct SQL statements. The number of tokens a value is allowed to contain is set via the optional maxToken argument. Defaults to 1.

isAcceptableQuotedParameter(value)

Returns true if the provided value is quoted correctly and can be used in an SQL statement.

escapeDoubleQuotes(value)

Returns the value parameter with all double quotation marks escaped (i. e. doubled).

escapeSingleQuotes(value)

Returns the value parameter with all single quotation marks escaped (i. e. doubled).

Troubleshooting

To enable tracing, you should set the environment variable DEBUG to hdbext:*.