Presto client

A Presto client for the Go programming language.

Features

• Native Go implementation
• Connections over HTTP or HTTPS
• HTTP Basic and Kerberos authentication
• Per-query user information for access control
• Support custom HTTP client (tunable conn pools, timeouts, TLS)
• Supports conversion from Presto to native Go data types
  • string, sql.NullString
  • int64, presto.NullInt64
  • float64, presto.NullFloat64
  • map, presto.NullMap
  • time.Time, presto.NullTime
  • Up to 3-dimensional arrays to Go slices, of any supported type

Requirements

• Go 1.8 or newer
• Presto 0.16x or newer

Installation

You need a working environment with Go installed and $GOPATH set.

Download and install presto database/sql driver:

go get github.com/prestodb/presto-go-client/presto

Make sure you have Git installed and in your $PATH.

Usage

This Presto client is an implementation of Go's database/sql/driver interface. In order to use it, you need to import the package and use the database/sql API then.

Only read operations are supported, such as SHOW and SELECT.

Use presto as driverName and a valid DSN as the dataSourceName.

Example:

import "database/sql"
import _ "github.com/prestodb/presto-go-client/presto"

dsn := "http://user@localhost:8080?catalog=default&schema=test"
db, err := sql.Open("presto", dsn)

Authentication

Both HTTP Basic and Kerberos authentication are supported.

HTTP Basic authentication

If the DSN contains a password, the client enables HTTP Basic authentication by setting the Authorization header in every request to presto.

HTTP Basic authentication is only supported on encrypted connections over HTTPS.

Kerberos authentication

This driver supports Kerberos authentication by setting up the Kerberos fields in the Config struct.

Please refer to the Coordinator Kerberos Authentication for server-side configuration.

System access control and per-query user information

It's possible to pass user information to presto, different from the principal used to authenticate to the coordinator. See the System Access Control documentation for details.

In order to pass user information in queries to presto, you have to add a NamedArg to the query parameters where the key is X-Presto-User. This parameter is used by the driver to inform presto about the user executing the query regardless of the authentication method for the actual connection, and its value is NOT passed to the query.

Example:

db.Query("SELECT * FROM foobar WHERE id=?", 1, sql.Named("X-Presto-User", string("Alice")))

The position of the X-Presto-User NamedArg is irrelevant and does not affect the query in any way.

DSN (Data Source Name)

The Data Source Name is a URL with a mandatory username, and optional query string parameters that are supported by this driver, in the following format:

http[s]://user[:pass]@host[:port][?parameters]

The easiest way to build your DSN is by using the Config.FormatDSN helper function.

The driver supports both HTTP and HTTPS. If you use HTTPS it's recommended that you also provide a custom http.Client that can validate (or skip) the security checks of the server certificate, and/or to configure TLS client authentication.

Parameters

Parameters are case-sensitive

Refer to the Presto Concepts documentation for more information.

source

Type:           string
Valid values:   string describing the source of the connection to presto
Default:        empty

The source parameter is optional, but if used, can help presto admins troubleshoot queries and trace them back to the original client.

catalog

Type:           string
Valid values:   the name of a catalog configured in the presto server
Default:        empty

The catalog parameter defines the presto catalog where schemas exist to organize tables.

schema

Type:           string
Valid values:   the name of an existing schema in the catalog
Default:        empty

The schema parameter defines the presto schema where tables exist. This is also known as namespace in some environments.

session_properties

Type:           string
Valid values:   comma-separated list of key=value session properties
Default:        empty

The session_properties parameter must contain valid parameters accepted by the presto server. Run SHOW SESSION in presto to get the current list.

custom_client

Type:           string
Valid values:   the name of a client previously registered to the driver
Default:        empty (defaults to http.DefaultClient)

The custom_client parameter allows the use of custom http.Client for the communication with presto.

Register your custom client in the driver, then refer to it by name in the DSN, on the call to sql.Open:

foobarClient := &http.Client{
    Transport: &http.Transport{
        Proxy: http.ProxyFromEnvironment,
        DialContext: (&net.Dialer{
            Timeout:   30 * time.Second,
            KeepAlive: 30 * time.Second,
            DualStack: true,
        }).DialContext,
        MaxIdleConns:          100,
        IdleConnTimeout:       90 * time.Second,
        TLSHandshakeTimeout:   10 * time.Second,
        ExpectContinueTimeout: 1 * time.Second,
        TLSClientConfig:       &tls.Config{
        // your config here...
        },
    },
}
presto.RegisterCustomClient("foobar", foobarClient)
db, err := sql.Open("presto", "https://user@localhost:8080?custom_client=foobar")

Examples

http://user@localhost:8080?source=hello&catalog=default&schema=foobar

https://user@localhost:8443?session_properties=query_max_run_time=10m,query_priority=2

License

As described in the LICENSE file.