QL adapter for upper.io/db.v1

The upper.io/db.v1/ql adapter for the QL is a wrapper of the github.com/cznic/ql/ql driver by Jan Mercl.

Installation

Use go get to download and install the adapter:

go get upper.io/db.v1/ql

Setting up database access

The ql.ConnectionURL{} struct is defined like this:

// ConnectionURL implements a SQLite connection struct.
type ConnectionURL struct {
  Database string
  Options  map[string]string
}

Alternatively, a ql.ParseURL() function is provided:

// ParseURL parses s into a ConnectionURL struct.
ql.ParseURL(s string) (ConnectionURL, error)

You may use ql.ConnectionURL as argument for db.Open().

Usage

To use this adapter, import upper.io/db.v1 and the upper.io/db.v1/ql packages.

# main.go
package main

import (
  "upper.io/db.v1"
  "upper.io/db.v1/ql"
)

Then, you can use the db.Open() method to open a QL database file:

var settings = ql.ConnectionURL{
  Database: `/path/to/example.db`, // Path to a QL database file.
}

sess, err = db.Open(ql.Adapter, settings)

Example

The following SQL statement creates a table with “name” and “born” columns.

--' example.sql

DROP TABLE IF EXISTS birthday;

CREATE TABLE birthday (
  name string,
  born time
);

Use the ql command line tool to create a example.db database file.

rm -f example.db
cat example.sql | ql -db example.db

The Go code below will add some rows to the “birthday” table and then will print the same rows that were inserted.

// example.go

package main

import (
  "fmt"
  "log"
  "time"
  "upper.io/db.v1"      // Imports the main db package.
  "upper.io/db.v1/ql"   // Imports the ql adapter.
)

var settings = ql.ConnectionURL{
  Database: `example.db`, // Path to database file.
}

type Birthday struct {
  // Maps the "Name" property to the "name" column of the "birthday" table.
  Name string `db:"name"`
  // Maps the "Born" property to the "born" column of the "birthday" table.
  Born time.Time `db:"born"`
}

func main() {

  // Attemping to open the "example.db" database file.
  sess, err := db.Open(ql.Adapter, settings)

  if err != nil {
    log.Fatalf("db.Open(): %q\n", err)
  }

  // Remember to close the database session.
  defer sess.Close()

  // Pointing to the "birthday" table.
  birthdayCollection, err := sess.Collection("birthday")

  if err != nil {
    log.Fatalf("sess.Collection(): %q\n", err)
  }

  // Attempt to remove existing rows (if any).
  err = birthdayCollection.Truncate()

  if err != nil {
    log.Fatalf("Truncate(): %q\n", err)
  }

  // Inserting some rows into the "birthday" table.

  birthdayCollection.Append(Birthday{
    Name: "Hayao Miyazaki",
    Born: time.Date(1941, time.January, 5, 0, 0, 0, 0, time.Local),
  })

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

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

  // Let's query for the results we've just inserted.
  var res db.Result

  res = birthdayCollection.Find()

  var birthday []Birthday

  // Query all results and fill the birthday variable with them.
  err = res.All(&birthday)

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

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

}

Running the example above:

go run main.go

Expected output:

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

Raw SQL

Sometimes you’ll need to run complex SQL queries with joins and database specific magic, there is an extra package sqlutil that you could use in this situation:

import "upper.io/db.v1/util/sqlutil"

This is an example for sqlutil.FetchRows:

  var sess db.Database
  var rows *sql.Rows
  var err error
  var drv *sql.DB

  type publication_t struct {
    Id       int64  `db:"id,omitempty"`
    Title    string `db:"title"`
    AuthorId int64  `db:"author_id"`
  }

  if sess, err = db.Open(Adapter, settings); err != nil {
    t.Fatal(err)
  }

  defer sess.Close()

  drv = sess.Driver().(*sql.DB)

  rows, err = drv.Query(`
    SELECT
      p.id,
      p.title AS publication_title,
      a.name AS artist_name
    FROM
      artist AS a,
      publication AS p
    WHERE
      a.id = p.author_id
  `)

  if err != nil {
    t.Fatal(err)
  }

  var all []publication_t

  // Mapping to an array.
  if err = sqlutil.FetchRows(rows, &all); err != nil {
    t.Fatal(err)
  }

  if len(all) != 9 {
    t.Fatalf("Expecting some rows.")
  }

You can also use sqlutil.FetchRow(*sql.Rows, interface{}) for mapping results obtained from sql.DB.Query() calls to a pointer of a single struct instead of a pointer to an array of structs. Please note that there is no support for sql.DB.QueryRow() and that you must provide a *sql.Rows value to both sqlutil.FetchRow() and sqlutil.FetchRows().

Using `db.Raw` and `db.Func`

If you need to provide a raw parameter for a method you can use the db.Raw type. Plese note that raw means that the specified value won’t be filtered:

res = sess.Find().Select(db.Raw{`DISTINCT(name)`})

db.Raw also works for condition values.

Another useful type that you could use to create an equivalent statement is db.Func:

res = sess.Find().Select(db.Func{`DISTINCT`, `name`})