Trino client

A Trino 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 Trino to native Go data types
  • string, sql.NullString
  • int64, sql.NullInt64
  • float64, sql.NullFloat64
  • map, trino.NullMap
  • time.Time, trino.NullTime
  • Up to 3-dimensional arrays to Go slices, of any supported type

Requirements

• Go 1.17 or newer
• Trino 372 or newer

Installation

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

Download and install Trino database/sql driver:

go get github.com/trinodb/trino-go-client/trino

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

Usage

This Trino 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 trino as driverName and a valid DSN as the dataSourceName.

Example:

import "database/sql"
import _ "github.com/trinodb/trino-go-client/trino"

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

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 Trino, 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 Trino, you have to add a NamedArg to the query parameters where the key is X-Trino-User. This parameter is used by the driver to inform Trino 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-Trino-User", string("Alice")))

The position of the X-Trino-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 Trino Concepts documentation for more information.

source

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

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

catalog

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

The catalog parameter defines the Trino 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 Trino 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 Trino server. Run SHOW SESSION in Trino 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 Trino.

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...
        },
    },
}
trino.RegisterCustomClient("foobar", foobarClient)
db, err := sql.Open("trino", "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

Data types

Query arguments

When passing arguments to queries, the driver supports the following Go data types:

• integers
• bool
• string
• slices
• trino.Numeric - a string representation of a number
• time.Time - passed to Trino as a timestamp with a time zone
• the result of trino.Date(year, month, day) - passed to Trino as a date
• the result of trino.Time(hour, minute, second, nanosecond) - passed to Trino as a time without a time zone
• the result of trino.TimeTz(hour, minute, second, nanosecond, location) - passed to Trino as a time with a time zone
• the result of trino.Timestamp(year, month, day, hour, minute, second, nanosecond) - passed to Trino as a timestamp without a time zone

It's not yet possible to pass:

• nil
• float32 or float64
• byte
• time.Duration
• json.RawMessage
• maps

To use the unsupported types, pass them as strings and use casts in the query, like so:

SELECT * FROM table WHERE col_double = cast(? AS DOUBLE) OR col_timestamp = CAST(? AS TIMESTAMP)

Response rows

When reading response rows, the driver supports most Trino data types, except:

• time and timestamps with precision - all time types are returned as time.Time. All precisions up to nanoseconds (TIMESTAMP(9) or TIME(9)) are supported (since this is the maximum precision Golang's time.Time supports). If a query returns columns defined with a greater precision, values will be trimmed to 9 decimal digits. Use CAST to reduce the returned precision, or convert the value to a string that then can be parsed manually.
• DECIMAL - returned as string
• IPADDRESS - returned as string
• INTERVAL YEAR TO MONTH and INTERVAL DAY TO SECOND - returned as string
• UUID - returned as string

Data types like HyperLogLog, SetDigest, QDigest, and TDigest are not supported and cannot be returned from a query.

For reading nullable columns, use:

• trino.NullTime
• trino.NullMap - which stores a map of map[string]interface{} or similar structs from the database/sql package, like sql.NullInt64

To read query results containing arrays or maps, pass one of the following structs to the Scan() function:

• trino.NullSliceBool
• trino.NullSliceString
• trino.NullSliceInt64
• trino.NullSliceFloat64
• trino.NullSliceTime
• trino.NullSliceMap

For two or three dimensional arrays, use trino.NullSlice2Bool and trino.NullSlice3Bool or equivalents for other data types.

To read ROW values, implement the sql.Scanner interface in a struct. Its Scan() function will receive a []interface{} slice, with values of the following types:

• bool
• json.Number for any numeric Trino types
• []interface{} for Trino arrays
• map[string]interface{} for Trino maps
• string for other Trino types, as character, date, time, or timestamp

License

As described in the LICENSE file.

Contributing

For contributing, development, and release guidelines, see CONTRIBUTING.md.