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golang-driver

A Go wrapper for the super performant and tunable DataStax C/C++ driver for Apache Cassandra.

Originally inspired by Matt Stump's golang-driver, this project evolved and added a lot of new features (e.g. support for all Cassandra data types, a simpler API that supports both simple and prepared statements in both sync and async flavors, cluster configuration options, etc.)

While this far this project has been my experiment in learning Go and interacting with the C/C++ driver for Cassandra, I think that the next stage of this project would be to benefit from the expertise of more experienced Go programmers.

If you are interested in continuing to develop this project, please drop me an email (alex at mypopescu dot com).

Build

  1. Build and install the DataStax C/C++ driver
  2. Install go get github.com/al3xandru/golang-driver/cassandra
  3. Run the example go run $GOPATH/src/github.com/al3xandru/golang-driver/examples/basic.go

Example Usage

package main

import (
	"fmt"
	"golang-driver/cassandra"
)

func main() {
	cluster := cassandra.NewCluster("127.0.0.1", "127.0.0.2")
	defer cluster.Close()

	session, err := cluster.Connect()
	if err != nil {
		fmt.Printf("Error connecting: %s\n", err.Error())
		return
	}
	defer session.Close()

	result, err := session.Exec("select keyspace_name from system.schema_keyspaces")
	if err != nil {
		fmt.Printf("Error executing: %s\n", err.Error())
		return
	}
	defer result.Close()

	fmt.Printf("Keyspaces:\n")
	for result.Next() {
		var keyspace string
		if err := result.Scan(&keyspace); err != nil {
			fmt.Printf("Row error: %s\n", err.Error())
			continue
		}
		fmt.Printf("%s\n", keyspace)
	}
}

See the tests in the main package for more examples.

What is supposed to work

  1. Connecting to a cluster (sort of minimal expectation) with support for some of the configuration options (not all options provided by the C/C++ driver are available)

  2. A range of basic Cassandra types, including the new ones introduced in version 2.2 (tinyint, smallint, date, time, timestamp).

    • There are a couple of missing data types (see To dos).
    • There's no support yet for UDTs

  3. Executing simple statements:

    session.Exec("select * from table where pk = ?", pk_value)

  4. Executing simple statements with non-default consistency settings:

    session.Query("select * from table where pk = ?", pk_value).
        WithConsistency(ANY).
        Exec()

  5. Executing prepared statements:

    pstmt := session.Prepare("select * from table where pk = ?")
pstmt.SetConsistency(ANY)
// once prepared you can reuse the prepared statement by
// binding new sets of parameters
for key := range keys {
    pstmt.Exec(key)
}

  6. There are similar functions for executing async statements which return a *cassandra.Future

Go types, driver types, and Cassandra data types

In order to expose all Cassandra types, this driver introduces some custom types whose usage should be fairly simple and self-explanatory. All of these types and their API can be found in types.go. Here's a short list:

  • Timestamp: corresponds to the timestamp data type and represents the seconds since Epoch
  • Date: corresponds to the date data type and holds a date without a time component
  • Time: corresponds to the time data type and represents a time within a day
  • UUID: for both uuid and timeuuid
  • Decimal: corresponds to the decimal data type and represents an arbitrary precision decimal number
  • Tuple: corresponds to the tuple data type.
Decimal

This library provides a very basic cassandra.Decimal type with just a couple of functions to allow you to store/retrieve the Cassandra decimal type.

In case you need more complete decimal libraries (that provide math operations on decimals), this is what I could find:

Converting from one of these to the cassandra.Decimal for storage should work without any problems.

Sets

Go doesn't have a Set-like type which makes it very hard to create an automatic mapping to a Cassandra set column with non-prepared statements. If prepared statements are used, then metadata about the target column is available and conversions from slices, arrays, and map[type]bool can be made.

This library offers a cassandra.Set() function that can wrap a slice, array, or map to make it aware that the target column is set.

If you are using prepared statements, you won't need this function.

Credits

  • go.uuid and uuid for inspiration on dealing with UUIDs
  • gocql for teaching me a lot about Go reflect
  • countless people on #go-nuts and Twitter

To do

  • Support for Cassandra 2.2 tinyint (int8) and smallint (int16) (CASSANDRA-8951
  • Support for Cassandra 2.2 date/time types (CASSANDRA-7523)
  • Binding values to statements
  • Read/Write Cassandra blob ([]byte) and inet (net.IP)
  • Prepared statements
  • Basic support for Cassandra uuid, timeuuid using cassandra.UUID struct
  • Advanced cluster configuration
  • Async API
  • Support for collections
  • Missing C* types: decimal, varint
  • Support for tuples (at least those using non-collections)
  • Support for UDTs
  • Named parameters
  • Unset (v4) vs null parameters
  • Batch statements

Copyright 2015-2016 Alex Popescu