Access data

This article walks you through extracting data using various methods, such as:

• Creating connections to data sources and running queries
• Using REST APIs
• Reading files into dataframe objects in your application.

Connections

With the Datagrok platform, you can programmatically retrieve data from different sources like files, databases, cloud, or webservices. Here's a general workflow for getting data:

1. Add a data connection to your package.
2. Specify the connection's parameters.
3. Transfer credentials.
4. Create a parameterized query and execute it in JavaScript code to return a dataframe.
5. Optional. Share a connection.

note

To learn how to create data connections from the UI, see documentation for the respective data source in the Access section of our documentation.

Creating a connection

To add a connection programmatically, first create a package. Packages can have multiple data connections in the connections folder. Create a separate JSON file with the required parameters for each connection.

Example

{
  "name": "ChEMBL",
  "parameters": {
    "server": "$GROK_DB_SERVER",
    "db": "chembl_24"
  },
  "dataSource": "PostgresDart",
  "description": "CHEMBL db",
  "tags": [
    "demo",
    "chem"
  ]
}

The name field is optional. If omitted, the filename (without the extension) is used as the connection name. Keep in mind that connection names are not case-sensitive.

Giving connection parameters in json is equivalent to completing these steps from the UI. For example, to connect to a database:

1. Go to Data > Databases.
2. Right-click the data source you want (for example, PostgreSQL) and select the context action Add new connection.

Our package utilities provide a similar template when running the grok add connection <name> command. See examples in Chembl or UsageAnalysis packages.

Connection parameters are specific to a data source. Most data providers require common parameters, such as:

• Data source
• Server
• Port
• DB
• Cache schema
• Cache results
• SSL
• Connection string
• Login
• Password
• Other parameters.

See Supported connectors for details.

When providing a connection string, you don't need to pass other parameters.

Parameters carrying sensitive data (such as Login/Password or Access Key/Secret Key) are handled in a special way.

Datagrok has a built-in credentials management system that protects sensitive data. Parameters regulating access to the data source are processed independently, so don't include them in a custom connection string.

Example: Specifying credentials for a data connection

{
  "name": "Northwind",
  "parameters": {
    "server": "dev.datagrok.ai",
    "port": 23306,
    "db": "Northwind",
    "cacheSchema": false,
    "cacheResults": false,
    "ssl": false,
    "connString": ""
  },
  "credentials": {
    "parameters": {
      "login": "",
      "password": ""
    }
  },
  "dataSource": "MariaDB",
  "description": "Northwind Connection",
  "tags": [
    "demo"
  ]
}

Instead, deploy a connection and send a POST request to $(GROK_HOST)/api/credentials/for/$(PACKAGE_NAME).$(CONNECTION_NAME) with the raw body containing JSON, like {"login": "abc", "password": "123"}, and headers {"Authorization": $(API_KEY), "Content-Type": "application/json"} (get the API key from your Datagrok profile page, for example https://public.datagrok.ai/u).

Querying data

Creating queries

Once the connection is established, you can extract data by sending a query to the data source. In a package, queries are typically placed in the queries folder.

Similar to scripts, you can annotate SQL statements with comments as the underlying mechanism is fundamentally the same (learn more about functions). To use an existing connection in a query, provide its name along with the namespace in the connection parameter.

Here's an example for your queries.sql file:

SQL query

--name: protein classification
--connection: chembl
select * from protein_classification
--end

SQL statements are annotated with comments, just like functions, since the underlying mechanism is essentially the same (read more on the concept of functions). Here we have two header parameters: the query name and the connection to use. In fact, this particular query could have been even simpler: there is no need to specify connection if the package only has one. Similarly, the tag end is not required if there is only one query per file: the parser needs it to understand where the current query ends and the next one begins. So safely omit the name of connection and/or the end tag if these conditions are met.

To use an existing connection in a query, specify its name along with the namespace in the connection parameter. For example, the above chembl connection that lives in the Chembl package has the following path: chembl:chembl. When browsing connections on the platform, you can identify such path by opening Links in the tab Details of the context panel.

If the package contains only one connection, the connection parameter can be omitted. Likewise, if there is just one query per file, the end tag isn't necessary, as the parser only needs it to differentiate between the end of one query and the beginning of another. Therefore, you can safely leave out the connection name and/or the end tag if these conditions are fulfilled.

tip

To quickly insert a query template into your package, type grok add query <name> in the terminal.

For a list of header parameters and further details related to query annotation, see Parameterized queries and Parameter annotation. For examples of data queries, see the Chembl package.

Running queries

There are several methods to execute queries. The most straightforward method is to run a query from the UI, which corresponds to entering $(PACKAGE_NAME):$(QUERY_NAME)() in the console, for example, Chembl:ProteinClassification().

In Datagrok, you can also call any function that can be executed in the console using Datagrok's JS API. This enables the use of corresponding methods in JavaScript:

grok.functions.call('Chembl:ProteinClassification')
  .then(t => grok.shell.addTableView(t));

Additionally, there is a dedicated method for queries that take the query name as a required parameter and several additional parameters (such as query parameters, ad hoc status, and the polling interval):

grok.data.query(`${PACKAGE_NAME}:${QUERY_NAME}`, {'parameter': 'value'}, true, 100);

To see how this method works, refer to this example.

Sharing connections

Data connections can be shared as part of a project , package (and repository containing this package), or as a standalone entity. The access rights of a database connection are inherited from the access rights of a query. However, the access rights of a query don't inherit the access rights of the database connection. Consequently, when sharing a query, the associated database connection will be shared automatically. However, sharing a connection does not automatically share your queries. In the case of web queries, they are shared automatically when the corresponding connection is shared.

Caching results

See Caching data.

Rest endpoints

Webservices provide endpoints that you can programmatically connect to. You can use the OpenAPI/Swagger format supported by Datagrok (see OpenAPI for details) or the platform's server to send a network request. The method used to proxy requests is similar to the standard fetch API:

const url = 'https://jsonplaceholder.typicode.com/posts';
const data = {name: 'username', password: 'password'};

grok.dapi.fetchProxy(url, {
  method: 'POST',
  headers: {'Content-Type': 'application/json'},
  body: JSON.stringify(data)
}).then(response => grok.shell.info(response.ok));

Reading files

In our JavaScript API examples, you can find methods that provide data for demonstration (grok.data.demo or grok.data.getDemoTable) and testing purposes (grok.data.testData). However, this section focuses on methods frequently used to deliver data to your applications.

Package files

To access data within your package (e.g. open a csv table), load it from an URL, as you would with other external files. The package root for client-side can be found with webRoot property. The example below retrieves the test.csv table from the data-samples subdirectory and opens a table view for it:

export let _package = new DG.Package();

grok.data.loadTable(`${_package.webRoot}data-samples/test.csv`)
  .then(t => grok.shell.addTableView(t));

File shares

Here's a basic example on how to retrieve data from an existing file share:

grok.functions.eval(`OpenServerFile("${USER}:Home/data.csv")`)
  .then(t => grok.shell.addTableView(t[0]));

In the example above, the script opens a dataframe using the file "data.csv" from a user's Home directory, which is created by default for all users upon signup.

To create a new connection in your package, create a JSON file with these parameters:

{
  "name": "New File Share",
  "parameters": {
    "dir": "/home/www/master/servergrok/data/demo",
    "indexFiles": true
  },
  "credentials": {
    "parameters": {
      "login": "",
      "password": ""
    }
  },
  "dataSource": "Files",
  "tags": [
    "demo"
  ]
}

Specify two parameters for the connection:

1. The directory you want to use
2. Whether you want to index files in that directory. If you do, an indexing data job will be created.

When referring to a file in your code, include the package and connection names before the file name. The path should be relative to what you previously specified in the dir parameter:

grok.functions.eval(`OpenServerFile("${PACKAGE_NAME}:${CONNECTION_NAME}/data.csv")`)
  .then(t => grok.shell.addTableView(t[0]));

Reading and writing files in file shares

The grok.dapi enables precise operations on files from file shares, such as writing, reading, checking existence, searching for presence by a pattern, renaming, moving, and deleting. For example, you can create a text file in your local file share like this:

grok.dapi.files.writeAsText('<YOUR_NAME>:Home/testFile.txt', 'Hello, world!');

All dapi.files methods accept three types of inputs:

• a fully specified file path, as seen in these examples
• a variable of the file type (see FileInfo), which may come, for example, from info panels working on files
• a string containing a file share connection GUID

All dapi.files methods are asynchronous.

For a comprehensive understanding of the files API, see this example.

Alternative methods for reading files

You can also use one of the following options to open files using JavaScript:

1. Define a function that takes an input of file type (see FileInfo): When you use this option, you can call file.readAsBytes() or file.readAsString() methods on this function. For example, by passing a string obtained from a file to grok.data.parseCsv(csv, options), you can customize the construction of a dataframe from comma-separated values. Alternatively, you can pass a file to a script to perform calculations and receive the results in your application's code.
2. Use grok.data.openTable(id): This method is helpful when replicating a process where you need to open a specific table by its ID. See this example.

See also:

• JavaScript Development
• Functions