CockroachDB adapter

The cockroachdb adapter for CockroachDB wraps the github.com/lib/pq driver written by Blake Mizerany.

Here you'll learn about the particularities of the CockroachDB adapter. Before starting to read this detailed information, it is advisable that you take a look at the getting started page so you become acquainted with the basics of upper/db and you can grasp concepts better.

Installation

Use go get to download and install the adapter:

go get github.com/upper/db/v4/adapter/cockroachdb

Setup

Database Session

Import the cockroachdb package into your application:

// main.go
package main

import (
  "github.com/upper/db/v4/adapter/cockroachdb"
)

Define the cockroachdb.ConnectionURL{} struct:

// ConnectionURL defines the DSN attributes.
type ConnectionURL struct {
  User     string
  Password string
  Host     string
  Database string
  Options  map[string]string
}

Pass the cockroachdb.ConnectionURL value as argument to cockroachdb.Open() so the session is created.

settings = cockroachdb.ConnectionURL{
  ...
}

sess, err = cockroachdb.Open(settings)
...

The cockroachdb.ParseURL() function is also provided in case you need to convert the DSN into a cockroachdb.ConnectionURL:

// ParseURL parses a DSN into a ConnectionURL struct.
cockroachdb.ParseURL(dsn string) (ConnectionURL, error)

Common Database Operations

Once the connection is established, you can start performing operations on the database.

Example

In the following example, a table named 'birthday' consisting of two columns ('name' and 'born') will be created. Before starting, the table will be searched in the database and, in the event it already exists, it will be removed. Then, three rows will be inserted into the table and checked for accuracy. To this end, the database will be queried and the matches (insertions) will be printed to standard output.

The birthday table with the name and born columns is created with these SQL statements:

--' example.sql
DROP TABLE IF EXISTS "birthday";

CREATE TABLE "birthday" (
  "name" CHARACTER VARYING(50),
  "born" TIMESTAMP
);

The psql command line tool is used to run the statements in the upperio_tests database:

cat example.sql | PGPASSWORD=upperio psql -Uupperio -h127.0.0.1 -p26257 upperio_tests

The rows are inserted into the birthday table. The database is queried for the insertions and is set to print them to standard output.

// example.go

package main

import (
  "fmt"
  "log"
  "time"

  "github.com/upper/db/v4/adapter/cockroachdb"
)

var settings = cockroachdb.ConnectionURL{
  Database: `upperio_tests`,  // Database name
  Host:     `localhost`,      // Server IP or name
  User:     `upperio`,        // Username
  Password: `upperio`,        // Password
}

type Birthday struct {
  // The 'name' column of the 'birthday' table
  // is mapped to the 'name' property.
  Name string `db:"name"`

  // The 'born' column of the 'birthday' table
  // is mapped to the 'born' property.
  Born time.Time `db:"born"`
}

func main() {

  // The database connection is attempted.
  sess, err := cockroachdb.Open(settings)
  if err != nil {
    log.Fatalf("db.Open(): %q\n", err)
  }
  defer sess.Close() // Closing the session is a good practice.

  // The 'birthday' table is referenced.
  birthdayCollection := sess.Collection("birthday")

  // Any rows that might have been added between the creation of
  // the table and the execution of this function are removed.
  err = birthdayCollection.Truncate()
  if err != nil {
    log.Fatalf("Truncate(): %q\n", err)
  }

  // Three rows are inserted into the 'Birthday' table.
  birthdayCollection.Insert(Birthday{
    Name: "Hayao Miyazaki",
    Born: time.Date(1941, time.January, 5, 0, 0, 0, 0, time.Local),
  })

  birthdayCollection.Insert(Birthday{
    Name: "Nobuo Uematsu",
    Born: time.Date(1959, time.March, 21, 0, 0, 0, 0, time.Local),
  })

  birthdayCollection.Insert(Birthday{
    Name: "Hironobu Sakaguchi",
    Born: time.Date(1962, time.November, 25, 0, 0, 0, 0, time.Local),
  })

  // The database is queried for the rows inserted.
  res := birthdayCollection.Find()

  // The 'birthdays' variable is filled with the results found.
  var birthdays []Birthday

  err = res.All(&birthdays)
  if err != nil {
    log.Fatalf("res.All(): %q\n", err)
  }

  // The 'birthdays' variable is printed to stdout.
  for _, birthday := range birthdays {
    fmt.Printf("%s was born in %s.\n",
      birthday.Name,
      birthday.Born.Format("January 2, 2006"),
    )
  }
}

The Go file is compiled and executed using go run:

go run example.go

The output consists of three rows including names and birthdates:

Hayao Miyazaki was born in January 5, 1941.
Nobuo Uematsu was born in March 21, 1959.
Hironobu Sakaguchi was born in November 25, 1962.

Specifications

JSON Types

You can save and retrieve data when using JSON types. If you want to try this out, make sure the column type is jsonb and the field type is cockroachdb.JSONB:

import (
  // ...
  "github.com/upper/db/v4/adapter/cockroachdb"
  // ...
)

type Person struct {
  ...
  Properties  cockroachdb.JSONB  `db:"properties"`
  Meta        cockroachdb.JSONB  `db:"meta"`
}

SQL builder

You can use the SQL builder for any complex SQL query:

q := sess.SQL().Select(
    "p.id",
    "p.title AD publication_title",
    "a.name AS artist_name",
  ).From("artists AS a", "publication AS p").
  Where("a.id = p.author_id")

var publications []Publication
if err = q.All(&publications); err != nil {
  log.Fatal(err)
}

Auto-incremental Keys (Serial)

If you want tables to generate a unique number automatically whenever a new record is inserted, you can use auto-incremental keys. In this case, the column must be defined as SERIAL.

In order for the ID to be returned by db.Collection.Insert(), the SERIAL column must be set as PRIMARY KEY too.

CREATE TABLE foo(
  id SERIAL PRIMARY KEY,
  title VARCHAR
);

Remember to use omitempty to specify that the ID field should be ignored if it has a zero value:

type Foo struct {
  ID    int64   `db:"id,omitempty"`
  Title string  `db:"title"`
}

otherwise, an error will be returned.

Escape Sequences

There might be characters that cannot be typed in the context you're working, or else would have an undesired interpretation. Through db.Func you can encode the syntactic entities that cannot be directly represented by the alphabet:

res = sess.Find().Select(db.Func("DISTINCT", "name"))

on the other hand, you can use the db.Raw function so a given value is taken literally:

res = sess.Find().Select(db.Raw("DISTINCT(name)"))

db.Raw can also be used as a condition argument, similarly to db.Cond.

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