pg

.env.example

@@ -1,3 +1,4 @@
 # sqlite (default): sqlite:///data/skeps.db
 # mysql: mysql://user:password@tcp(mysql:3306)/skeps
+# postgres: postgres://user:password@postgres:5432/skeps?sslmode=disable
 DATABASE_URL=sqlite:///data/skeps.db

backend/db.go

@@ -3,9 +3,11 @@ package main
 import (
 	"database/sql"
 	"fmt"
+	"strconv"
 	"strings"
 
 	_ "github.com/go-sql-driver/mysql"
+	_ "github.com/lib/pq"
 	_ "modernc.org/sqlite"
 )
 
@@ -58,10 +60,88 @@ CREATE TABLE IF NOT EXISTS items (
 	FOREIGN KEY (sublist_id) REFERENCES sublists(id)
 );`
 
-func openDB(databaseURL string) (*sql.DB, error) {
+const postgresSchema = `
+CREATE TABLE IF NOT EXISTS lists (
+	id TEXT PRIMARY KEY,
+	created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+);
+CREATE TABLE IF NOT EXISTS sublists (
+	id SERIAL PRIMARY KEY,
+	list_id TEXT NOT NULL REFERENCES lists(id),
+	name TEXT NOT NULL,
+	color TEXT NOT NULL,
+	created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+);
+CREATE TABLE IF NOT EXISTS items (
+	id SERIAL PRIMARY KEY,
+	list_id TEXT NOT NULL REFERENCES lists(id),
+	name TEXT NOT NULL,
+	quantity INTEGER NOT NULL DEFAULT 1,
+	done BOOLEAN NOT NULL DEFAULT FALSE,
+	position DOUBLE PRECISION NOT NULL DEFAULT 0,
+	sublist_id INTEGER REFERENCES sublists(id),
+	created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+);`
+
+// querier is the subset of *sql.DB every handler uses. Postgres needs its own
+// implementation since, unlike sqlite and mysql, it takes $1-style positional
+// placeholders instead of "?" and has no LastInsertId support.
+type querier interface {
+	Exec(query string, args ...any) (sql.Result, error)
+	Query(query string, args ...any) (*sql.Rows, error)
+	QueryRow(query string, args ...any) *sql.Row
+	insertReturningID(query string, args ...any) (int64, error)
+}
+
+type stdDB struct{ *sql.DB }
+
+func (d stdDB) insertReturningID(query string, args ...any) (int64, error) {
+	res, err := d.DB.Exec(query, args...)
+	if err != nil {
+		return 0, err
+	}
+	return res.LastInsertId()
+}
+
+type pgDB struct{ *sql.DB }
+
+func rebindPositional(query string) string {
+	var b strings.Builder
+	n := 0
+	for _, r := range query {
+		if r == '?' {
+			n++
+			b.WriteByte('$')
+			b.WriteString(strconv.Itoa(n))
+		} else {
+			b.WriteRune(r)
+		}
+	}
+	return b.String()
+}
+
+func (d pgDB) Exec(query string, args ...any) (sql.Result, error) {
+	return d.DB.Exec(rebindPositional(query), args...)
+}
+
+func (d pgDB) Query(query string, args ...any) (*sql.Rows, error) {
+	return d.DB.Query(rebindPositional(query), args...)
+}
+
+func (d pgDB) QueryRow(query string, args ...any) *sql.Row {
+	return d.DB.QueryRow(rebindPositional(query), args...)
+}
+
+func (d pgDB) insertReturningID(query string, args ...any) (int64, error) {
+	var id int64
+	err := d.DB.QueryRow(rebindPositional(query)+" RETURNING id", args...).Scan(&id)
+	return id, err
+}
+
+func openDB(databaseURL string) (*sql.DB, querier, error) {
 	driver, dsn, found := strings.Cut(databaseURL, "://")
 	if !found {
-		return nil, fmt.Errorf("DATABASE_URL must be in the form driver://dsn, got %q", databaseURL)
+		return nil, nil, fmt.Errorf("DATABASE_URL must be in the form driver://dsn, got %q", databaseURL)
 	}
 
 	var schema string
@@ -69,23 +149,26 @@ func openDB(databaseURL string) (*sql.DB, error) {
 	case "sqlite":
 		schema = sqliteSchema
 	case "mysql":
-		driver = "mysql"
 		schema = mysqlSchema
+	case "postgres", "postgresql":
+		driver = "postgres"
+		dsn = databaseURL // lib/pq expects the full URL, scheme included
+		schema = postgresSchema
 	default:
-		return nil, fmt.Errorf("unsupported database driver %q, expected sqlite or mysql", driver)
+		return nil, nil, fmt.Errorf("unsupported database driver %q, expected sqlite, mysql or postgres", driver)
 	}
 
 	db, err := sql.Open(driver, dsn)
 	if err != nil {
-		return nil, fmt.Errorf("opening database: %w", err)
+		return nil, nil, fmt.Errorf("opening database: %w", err)
 	}
 
 	if err := db.Ping(); err != nil {
-		return nil, fmt.Errorf("connecting to database: %w", err)
+		return nil, nil, fmt.Errorf("connecting to database: %w", err)
 	}
 
 	if _, err := db.Exec(schema); err != nil {
-		return nil, fmt.Errorf("running migration: %w", err)
+		return nil, nil, fmt.Errorf("running migration: %w", err)
 	}
 
 	// Best-effort: adds columns for databases created before they existed.
@@ -93,5 +176,8 @@ func openDB(databaseURL string) (*sql.DB, error) {
 	db.Exec("ALTER TABLE items ADD COLUMN position REAL NOT NULL DEFAULT 0")
 	db.Exec("ALTER TABLE items ADD COLUMN sublist_id INTEGER")
 
-	return db, nil
+	if driver == "postgres" {
+		return db, pgDB{db}, nil
+	}
+	return db, stdDB{db}, nil
 }

backend/go.mod

@@ -13,6 +13,7 @@ require (
 	github.com/dustin/go-humanize v1.0.1 // indirect
 	github.com/google/uuid v1.6.0 // indirect
 	github.com/hashicorp/golang-lru/v2 v2.0.7 // indirect
+	github.com/lib/pq v1.12.3 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/ncruces/go-strftime v0.1.9 // indirect
 	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect

backend/go.sum

@@ -12,6 +12,8 @@ github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
 github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/hashicorp/golang-lru/v2 v2.0.7 h1:a+bsQ5rvGLjzHuww6tVxozPZFVghXaHOwFs4luLUK2k=
 github.com/hashicorp/golang-lru/v2 v2.0.7/go.mod h1:QeFd9opnmA6QUJc5vARoKUSoFhyfM2/ZepoAG6RGpeM=
+github.com/lib/pq v1.12.3 h1:tTWxr2YLKwIvK90ZXEw8GP7UFHtcbTtty8zsI+YjrfQ=
+github.com/lib/pq v1.12.3/go.mod h1:/p+8NSbOcwzAEI7wiMXFlgydTwcgTr3OSKMsD2BitpA=
 github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=
 github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
 github.com/ncruces/go-strftime v0.1.9 h1:bY0MQC28UADQmHmaF5dgpLmImcShSi2kHU9XLdhx/f4=

backend/handlers.go

@@ -31,7 +31,7 @@ type Sublist struct {
 }
 
 type api struct {
-	db  *sql.DB
+	db  querier
 	hub *hub
 }
 
@@ -132,12 +132,11 @@ func (a *api) createSublist(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	res, err := a.db.Exec("INSERT INTO sublists (list_id, name, color) VALUES (?, ?, ?)", listID, in.Name, in.Color)
+	id, err := a.db.insertReturningID("INSERT INTO sublists (list_id, name, color) VALUES (?, ?, ?)", listID, in.Name, in.Color)
 	if err != nil {
 		writeError(w, http.StatusInternalServerError, err.Error())
 		return
 	}
-	id, _ := res.LastInsertId()
 
 	var s Sublist
 	err = a.db.QueryRow("SELECT id, name, color, created_at FROM sublists WHERE id = ?", id).
@@ -238,12 +237,11 @@ func (a *api) createItem(w http.ResponseWriter, r *http.Request) {
 	}
 	position := maxPosition.Float64 + 1
 
-	res, err := a.db.Exec("INSERT INTO items (list_id, name, quantity, position, sublist_id) VALUES (?, ?, ?, ?, ?)", listID, in.Name, in.Quantity, position, in.SublistID)
+	id, err := a.db.insertReturningID("INSERT INTO items (list_id, name, quantity, position, sublist_id) VALUES (?, ?, ?, ?, ?)", listID, in.Name, in.Quantity, position, in.SublistID)
 	if err != nil {
 		writeError(w, http.StatusInternalServerError, err.Error())
 		return
 	}
-	id, _ := res.LastInsertId()
 
 	var it Item
 	err = a.db.QueryRow("SELECT id, name, quantity, done, position, sublist_id, created_at FROM items WHERE id = ?", id).

backend/main.go

@@ -12,11 +12,11 @@ func main() {
 		databaseURL = "sqlite://./skeps.db"
 	}
 
-	db, err := openDB(databaseURL)
+	rawDB, db, err := openDB(databaseURL)
 	if err != nil {
 		log.Fatalf("database: %v", err)
 	}
-	defer db.Close()
+	defer rawDB.Close()
 
 	a := &api{db: db, hub: newHub()}