KSQL the Keep it Simple SQL library

KSQL was created to offer an actually simple and satisfactory tool for interacting with SQL Databases in Golang.

The core goal of KSQL is not to offer new features that are unavailable on other libraries (although we do have some), but to offer a well-thought and well-planned API so that users have an easier time, learning, debugging, and avoiding common pitfalls.

KSQL is also decoupled from its backend so that the actual communication with the database is performed by well-known and trusted technologies, namely: pgx and database/sql. You can even create your own backend adapter for KSQL which is useful in some situations.

In this README you will find examples for "Getting Started" with the library, for more advanced use-cases please read our Wiki.

Let's start with some Code:

This short example below is a TLDR version for illustrating how easy it is to use KSQL.

You will find more complete examples on the sections below.

package main

import (
	"context"
	"fmt"
	"log"
	"os"

	"github.com/vingarcia/ksql"
	"github.com/vingarcia/ksql/adapters/kpgx"
)

var UsersTable = ksql.NewTable("users", "user_id")

type User struct {
	ID   int    `ksql:"user_id"`
	Name string `ksql:"name"`
	Type string `ksql:"type"`
}

func main() {
	ctx := context.Background()
	db, err := kpgx.New(ctx, os.Getenv("POSTGRES_URL"), ksql.Config{})
	if err != nil {
		log.Fatalf("unable connect to database: %s", err)
	}
	defer db.Close()

	// For querying only some attributes you can
	// create a custom struct like this:
	var count []struct {
		Count string `ksql:"count"`
		Type string `ksql:"type"`
	}
	err = db.Query(ctx, &count, "SELECT type, count(*) as count FROM users WHERE type = $1 GROUP BY type", "admin")
	if err != nil {
		log.Fatalf("unable to query users: %s", err)
	}

	fmt.Println("number of users by type:", count)

	// For loading entities from the database KSQL can build
	// the SELECT part of the query for you if you omit it like this:
	var users []User
	err = db.Query(ctx, &users, "FROM users WHERE type = $1", "admin")
	if err != nil {
		log.Fatalf("unable to query users: %s", err)
	}

	fmt.Println("users:", users)
}

We currently have 4 constructors available, one of them is illustrated above (kpgx.New()), the other ones have the exact same signature but work on different databases, they are:

kpgx.New(ctx, os.Getenv("DATABASE_URL"), ksql.Config{}) for Postgres, it works on top of pgxpool
kmysql.New(ctx, os.Getenv("DATABASE_URL"), ksql.Config{}) for MySQL, it works on top of database/sql
ksqlserver.New(ctx, os.Getenv("DATABASE_URL"), ksql.Config{}) for SQLServer, it works on top of database/sql
ksqlite3.New(ctx, os.Getenv("DATABASE_URL"), ksql.Config{}) for SQLite3, it works on top of database/sql

The KSQL Interface

The current interface contains the methods the users are expected to use, and it is also used for making it easy to mock the whole library if needed.

This interface is declared in the project as ksql.Provider and is displayed below.

We plan on keeping it very simple with a small number of well thought functions that cover all use-cases, so don't expect many additions:

// Provider describes the KSQL public behavior
//
// The Insert, Patch, Delete and QueryOne functions return `ksql.ErrRecordNotFound`
// if no record was found or no rows were changed during the operation.
type Provider interface {
	Insert(ctx context.Context, table Table, record interface{}) error
	Patch(ctx context.Context, table Table, record interface{}) error
	Delete(ctx context.Context, table Table, idOrRecord interface{}) error

	Query(ctx context.Context, records interface{}, query string, params ...interface{}) error
	QueryOne(ctx context.Context, record interface{}, query string, params ...interface{}) error
	QueryChunks(ctx context.Context, parser ChunkParser) error

	Exec(ctx context.Context, query string, params ...interface{}) (Result, error)
	Transaction(ctx context.Context, fn func(Provider) error) error
}

Using KSQL

In the example below we'll cover all the most common use-cases such as:

Inserting records
Updating records
Deleting records
Querying one or many records
Making transactions

More advanced use cases are illustrated on their own pages on our Wiki:

For the more common use-cases please read the example below, which is also available here if you want to compile it yourself.

package main

import (
	"context"
	"fmt"

	"github.com/vingarcia/ksql"
	"github.com/vingarcia/ksql/adapters/ksqlite3"
	"github.com/vingarcia/ksql/nullable"
)

// User ...
type User struct {
	ID   int    `ksql:"id"`
	Name string `ksql:"name"`
	Age  int    `ksql:"age"`

	// This field will be saved as JSON in the database
	Address Address `ksql:"address,json"`
}

// PartialUpdateUser ...
type PartialUpdateUser struct {
	ID      int      `ksql:"id"`
	Name    *string  `ksql:"name"`
	Age     *int     `ksql:"age"`
	Address *Address `ksql:"address,json"`
}

// Address ...
type Address struct {
	State string `json:"state"`
	City  string `json:"city"`
}

// UsersTable informs KSQL the name of the table and that it can
// use the default value for the primary key column name: "id"
var UsersTable = ksql.NewTable("users")

func main() {
	ctx := context.Background()

	// The available adapters are:
	// - kpgx.New(ctx, connURL, ksql.Config{})
	// - kmysql.New(ctx, connURL, ksql.Config{})
	// - ksqlserver.New(ctx, connURL, ksql.Config{})
	// - ksqlite3.New(ctx, connURL, ksql.Config{})
	//
	// For more detailed examples see:
	// - `./examples/all_adapters/all_adapters.go`
	//
	// In this example we'll use sqlite3:
	db, err := ksqlite3.New(ctx, "/tmp/hello.sqlite", ksql.Config{
		MaxOpenConns: 1,
	})
	if err != nil {
		panic(err.Error())
	}
	defer db.Close()

	// In the definition below, please note that BLOB is
	// the only type we can use in sqlite for storing JSON.
	_, err = db.Exec(ctx, `CREATE TABLE IF NOT EXISTS users (
	  id INTEGER PRIMARY KEY,
		age INTEGER,
		name TEXT,
		address BLOB
	)`)
	if err != nil {
		panic(err.Error())
	}

	var alison = User{
		Name: "Alison",
		Age:  22,
		Address: Address{
			State: "MG",
		},
	}
	err = db.Insert(ctx, UsersTable, &alison)
	if err != nil {
		panic(err.Error())
	}
	fmt.Println("Alison ID:", alison.ID)

	// Inserting inline:
	err = db.Insert(ctx, UsersTable, &User{
		Name: "Cristina",
		Age:  27,
		Address: Address{
			State: "SP",
		},
	})
	if err != nil {
		panic(err.Error())
	}

	// Deleting Alison:
	err = db.Delete(ctx, UsersTable, alison.ID)
	if err != nil {
		panic(err.Error())
	}

	// Retrieving Cristina, note that if you omit the SELECT part of the query
	// KSQL will build it for you (efficiently) based on the fields from the struct:
	var cris User
	err = db.QueryOne(ctx, &cris, "FROM users WHERE name = ? ORDER BY id", "Cristina")
	if err != nil {
		panic(err.Error())
	}
	fmt.Printf("Cristina: %#v\n", cris)

	// Updating all fields from Cristina:
	cris.Name = "Cris"
	err = db.Patch(ctx, UsersTable, cris)

	// Changing the age of Cristina but not touching any other fields:

	// Partial update technique 1:
	err = db.Patch(ctx, UsersTable, struct {
		ID  int `ksql:"id"`
		Age int `ksql:"age"`
	}{ID: cris.ID, Age: 28})
	if err != nil {
		panic(err.Error())
	}

	// Partial update technique 2:
	err = db.Patch(ctx, UsersTable, PartialUpdateUser{
		ID:  cris.ID,
		Age: nullable.Int(28), // (just a pointer to an int, if null it won't be updated)
	})
	if err != nil {
		panic(err.Error())
	}

	// Listing first 10 users from the database
	// (each time you run this example a new Cristina is created)
	//
	// Note: Using this function it is recommended to set a LIMIT, since
	// not doing so can load too many users on your computer's memory or
	// cause an Out Of Memory Kill.
	//
	// If you need to query very big numbers of users we recommend using
	// the `QueryChunks` function.
	var users []User
	err = db.Query(ctx, &users, "FROM users LIMIT 10")
	if err != nil {
		panic(err.Error())
	}

	fmt.Printf("Users: %#v\n", users)

	// Making transactions:
	err = db.Transaction(ctx, func(db ksql.Provider) error {
		var cris2 User
		err = db.QueryOne(ctx, &cris2, "FROM users WHERE id = ?", cris.ID)
		if err != nil {
			// This will cause an automatic rollback:
			return err
		}

		err = db.Patch(ctx, UsersTable, PartialUpdateUser{
			ID:  cris2.ID,
			Age: nullable.Int(29),
		})
		if err != nil {
			// This will also cause an automatic rollback and then panic again
			// so that we don't hide the panic inside the KSQL library
			panic(err.Error())
		}

		// Commits the transaction
		return nil
	})
	if err != nil {
		panic(err.Error())
	}
}

Benchmark Comparison

The results of the benchmark are good: they show that KSQL is in practical terms, as fast as sqlx which was our goal from the start.

To understand the benchmark below you must know that all tests are performed using Postgres 12.1 and that we are comparing the following tools:

KSQL using the adapter that wraps database/sql
KSQL using the adapter that wraps pgx
database/sql
sqlx
pgx (with pgxpool)
gorm
sqlc
sqlboiler

For each of these tools we are running 3 different queries:

The insert-one query looks like:

INSERT INTO users (name, age) VALUES ($1, $2) RETURNING id

The single-row query looks like:

SELECT id, name, age FROM users OFFSET $1 LIMIT 1

The multiple-rows query looks like:

SELECT id, name, age FROM users OFFSET $1 LIMIT 10

Keep in mind that some of the tools tested (like GORM) actually build the queries internally so the actual code used for the benchmark might differ a little bit from the example ones above.

Without further ado, here are the results:

$ make bench TIME=5s
sqlc generate
go test -bench=. -benchtime=5s
goos: linux
goarch: amd64
pkg: github.com/vingarcia/ksql/benchmarks
cpu: Intel(R) Core(TM) i7-10750H CPU @ 2.60GHz
BenchmarkInsert/ksql/sql-adapter/insert-one-12         	    9256	    626985 ns/op
BenchmarkInsert/ksql/pgx-adapter/insert-one-12         	   11056	    548748 ns/op
BenchmarkInsert/sql/insert-one-12                      	    9565	    623659 ns/op
BenchmarkInsert/sql/prep-stmt/insert-one-12            	   10000	    541058 ns/op
BenchmarkInsert/sqlx/insert-one-12                     	    9319	    637775 ns/op
BenchmarkInsert/sqlx/prep-stmt/insert-one-12           	   10000	    549806 ns/op
BenchmarkInsert/pgxpool/insert-one-12                  	   10000	    546349 ns/op
BenchmarkInsert/gorm/insert-one-12                     	    8859	    675650 ns/op
BenchmarkInsert/sqlc/insert-one-12                     	    9889	    634589 ns/op
BenchmarkInsert/sqlc/prep-stmt/insert-one-12           	   10000	    552079 ns/op
BenchmarkInsert/sqlboiler/insert-one-12                	    9536	    633515 ns/op
BenchmarkQuery/ksql/sql-adapter/single-row-12          	   41222	    144799 ns/op
BenchmarkQuery/ksql/sql-adapter/multiple-rows-12       	   38523	    156556 ns/op
BenchmarkQuery/ksql/pgx-adapter/single-row-12          	   85074	     72465 ns/op
BenchmarkQuery/ksql/pgx-adapter/multiple-rows-12       	   70690	     84502 ns/op
BenchmarkQuery/sql/single-row-12                       	   41802	    144467 ns/op
BenchmarkQuery/sql/multiple-rows-12                    	   39248	    147765 ns/op
BenchmarkQuery/sql/prep-stmt/single-row-12             	   80530	     71376 ns/op
BenchmarkQuery/sql/prep-stmt/multiple-rows-12          	   76730	     77769 ns/op
BenchmarkQuery/sqlx/single-row-12                      	   41960	    146817 ns/op
BenchmarkQuery/sqlx/multiple-rows-12                   	   39349	    152887 ns/op
BenchmarkQuery/sqlx/prep-stmt/single-row-12            	   81045	     73004 ns/op
BenchmarkQuery/sqlx/prep-stmt/multiple-rows-12         	   75256	     78604 ns/op
BenchmarkQuery/pgxpool/single-row-12                   	   82630	     72241 ns/op
BenchmarkQuery/pgxpool/multiple-rows-12                	   81619	     74408 ns/op
BenchmarkQuery/gorm/single-row-12                      	   76700	     78651 ns/op
BenchmarkQuery/gorm/multiple-rows-12                   	   62342	     95746 ns/op
BenchmarkQuery/sqlc/single-row-12                      	   41563	    146143 ns/op
BenchmarkQuery/sqlc/multiple-rows-12                   	   40240	    149534 ns/op
BenchmarkQuery/sqlc/prep-stmt/single-row-12            	   83230	     72397 ns/op
BenchmarkQuery/sqlc/prep-stmt/multiple-rows-12         	   79408	     78645 ns/op
BenchmarkQuery/sqlboiler/single-row-12                 	   65866	     93841 ns/op
BenchmarkQuery/sqlboiler/multiple-rows-12              	   65091	     94486 ns/op
PASS
ok  	github.com/vingarcia/ksql/benchmarks	226.109s
Benchmark executed at: 2022-11-13
Benchmark executed on commit: 5bfb5cd92affae29dab3499b07fcd36b70a20057

Running the KSQL tests (for contributors)

The tests use docker-test for setting up all the supported databases, which means that:

You need to have docker installed
You must be able to run docker without sudo, i.e. if you are not root you should add yourself to the docker group, e.g.:
```
$ sudo usermod <your_username> -aG docker
```
And then restart your login session (or just reboot)

After that you can just run the tests by using:

make test

But it is recommended to first download the required images using:

docker pull postgres:14.0
docker pull mysql:8.0.27
docker pull mcr.microsoft.com/mssql/server:2017-latest

Otherwise the first attempt to run the tests will spend a long time downloading these images and then fail because the TestMain() function is configured to kill the containers after 20 seconds.

TODO List

Add support for serializing structs as other formats such as YAML
Update ksqltest.FillStructWith to work with ksql:"..,json" tagged attributes
Create a way for users to submit user defined dialects
Improve error messages (ongoing)
Add support for the Patch function to work with maps for partial updates
Add support for the Insert function to work with maps
Add support for a ksql.Array(params ...interface{}) for allowing queries like this: db.Query(ctx, &user, "SELECT * FROM user WHERE id in (?)", ksql.Array(1,2,3))
Improve docs about ksql.Mock

Optimization Oportunities

Test if using a pointer on the field info is faster or not
Consider passing the cached structInfo as argument for all the functions that use it, so that we don't need to get it more than once in the same call.
Use a cache to store often used queries (like pgx)
Preload the insert method for all dialects inside ksql.NewTable()
Use prepared statements for the helper functions, Update, Insert and Delete.

Features for a possible V2

Change the .Transaction(db ksql.Provider) to a .Transaction(ctx context.Context)
Make the .Query() method to return a type Query interface { One(); All(); Chunks(); }
Have an Update() method that updates without ignoring NULLs as Patch() does
Rename NewTable() to just Table() so it feels right to declare it inline when convenient

douglaszuqueto/ksql