Backup databases before migrating

.gitea/workflows/build.yml

@@ -7,5 +7,10 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
 
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '>=1.24'
+
       - name: Test
         run: go test . -v

README.md

@@ -0,0 +1,92 @@
+# MySQLite
+
+A Go library that provides a convenient wrapper around SQLite with additional functionality for database management, migrations, and transactions.
+
+## Features
+
+- Simple and intuitive SQLite database connection management
+- Thread-safe database operations with built-in locking mechanism
+- Support for database migrations
+- Transaction management
+- Built on top of [zombiezen.com/go/sqlite](https://pkg.go.dev/zombiezen.com/go/sqlite)
+
+## Installation
+
+```bash
+go get gitea.seeseepuff.be/seeseemelk/mysqlite
+```
+
+## Usage
+
+### Opening a Database Connection
+
+```go
+import "gitea.seeseepuff.be/seeseemelk/mysqlite"
+
+// Open an in-memory database
+db, err := mysqlite.OpenDb(":memory:")
+if err != nil {
+    // Handle error
+}
+defer db.Close()
+
+// Open a file-based database
+db, err := mysqlite.OpenDb("path/to/database.db")
+if err != nil {
+    // Handle error
+}
+defer db.Close()
+```
+
+### Executing Queries
+
+The library provides methods for executing SQL queries and managing transactions:
+
+```go
+// Execute a simple query
+err := db.Query("CREATE TABLE users (id INTEGER PRIMARY KEY, name TEXT)").Exec()
+
+// Use transactions
+tx, err := db.BeginTransaction()
+if err != nil {
+    // Handle error
+}
+
+// Perform operations within transaction
+// ...
+
+// Commit or rollback
+err = tx.Commit() // or tx.Rollback()
+```
+
+### Database Migrations
+
+The library includes support for SQL-based migrations. Migrations are SQL files stored in a directory and are executed in order based on their filename prefix:
+
+1. Create a directory for your migrations (e.g., `migrations/`)
+2. Add numbered SQL migration files:
+   ```
+   migrations/
+   ├── 1_initial.sql
+   ├── 2_add_users.sql
+   ├── 3_add_posts.sql
+   ```
+3. Embed the migrations in your Go code:
+   ```go
+   import "embed"
+   
+   //go:embed migrations/*.sql
+   var migrations embed.FS
+   
+   // Apply migrations
+   err := db.MigrateDb(migrations, "migrations")
+   if err != nil {
+       // Handle error
+   }
+   ```
+
+Each migration file should contain valid SQL statements. The migrations are executed in order and are tracked internally to ensure they only run once.
+
+## Requirements
+
+- Go 1.24 or higher

database.go

@@ -2,12 +2,15 @@ package mysqlite
 
 import (
 	"fmt"
+	"sync"
 	"zombiezen.com/go/sqlite"
 )
 
 // Db holds a connection to a SQLite database.
 type Db struct {
 	Db     *sqlite.Conn
+	source string
+	lock   sync.Mutex
 }
 
 // OpenDb opens a new connection to a SQLite database.
@@ -19,7 +22,7 @@ func OpenDb(databaseSource string) (*Db, error) {
 	if err != nil {
 		return nil, err
 	}
-	return &Db{Db: conn}, nil
+	return &Db{Db: conn, source: databaseSource}, nil
 }
 
 // Close closes the database.
@@ -35,3 +38,11 @@ func (d *Db) MustClose() {
 		panic(fmt.Sprintf("error closing db: %v", err))
 	}
 }
+
+func (d *Db) Lock() {
+	d.lock.Lock()
+}
+
+func (d *Db) Unlock() {
+	d.lock.Unlock()
+}

migrator.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"io/fs"
 	"log"
+	"os"
 	"path"
 	"strconv"
 	"strings"
@@ -40,6 +41,20 @@ func (d *Db) MigrateDb(filesystem ReadDirFileFS, directory string) error {
 	}
 	log.Printf("Current version is %d, max migration version is %d", currentVersion, latestVersion)
 
+	// Create a backup if we're not on the latest version
+	if currentVersion != latestVersion && d.source != ":memory:" {
+		target := d.source + ".backup." + strconv.Itoa(currentVersion)
+		log.Printf("Creating backup of database to %s", target)
+		data, err := d.Db.Serialize("main")
+		if err != nil {
+			return fmt.Errorf("error serializing database: %v", err)
+		}
+		err = os.WriteFile(target, data, 0644)
+		if err != nil {
+			return fmt.Errorf("error writing backup: %v", err)
+		}
+	}
+
 	// If we are no up-to-date, bring the db up-to-date
 	for currentVersion != latestVersion {
 		targetVersion := currentVersion + 1
@@ -50,7 +65,7 @@ func (d *Db) MigrateDb(filesystem ReadDirFileFS, directory string) error {
 			return fmt.Errorf("error opening migration script %s: %v", migrationScript, err)
 		}
 
-		err = performSingleMigration(err, d, migrationScript, targetVersion)
+		err = performSingleMigration(d, migrationScript, targetVersion)
 		if err != nil {
 			return err
 		}
@@ -61,14 +76,23 @@ func (d *Db) MigrateDb(filesystem ReadDirFileFS, directory string) error {
 	return nil
 }
 
-func performSingleMigration(err error, d *Db, migrationScript []byte, targetVersion int) error {
+func performSingleMigration(d *Db, migrationScript []byte, targetVersion int) error {
+	script := string(migrationScript)
+	// Split script based on semicolon
+	statements := strings.Split(script, ";")
+
 	tx, err := d.Begin()
 	if err != nil {
 		return fmt.Errorf("error beginning transaction: %v", err)
 	}
 	defer tx.MustRollback()
 
-	err = tx.Query(string(migrationScript)).Exec()
+	for _, statement := range statements {
+		statement = strings.TrimSpace(statement)
+		if statement == "" {
+			continue
+		}
+		err = tx.Query(statement).Exec()
 		if err != nil {
 			return fmt.Errorf("error performing migration: %v", err)
 		}
@@ -78,6 +102,8 @@ func performSingleMigration(err error, d *Db, migrationScript []byte, targetVers
 			return fmt.Errorf("error updating version: %v", err)
 		}
 
+	}
+
 	err = tx.Commit()
 	if err != nil {
 		return fmt.Errorf("error commiting transaction: %v", err)

migrator_test.go

@@ -17,4 +17,8 @@ func TestDb_MigrateDb(t *testing.T) {
 	var count int
 	db.Query("select count(*) from mydata").MustScanSingle(&count)
 	require.Equal(t, 1, count, "incorrect number of rows in database")
+
+	count = 0
+	db.Query("select count(*) from multiTable").MustScanSingle(&count)
+	require.Equal(t, 1, count, "incorrect number of rows in database")
 }

query.go

@@ -2,16 +2,27 @@ package mysqlite
 
 import (
 	"fmt"
+	"iter"
 	"reflect"
 	"zombiezen.com/go/sqlite"
 )
 
 type Query struct {
 	stmt *sqlite.Stmt
+	// Reference to the database. If set, it is assumed that a lock was taken
+	// by the query that should be freed by the query.
+	db  *Db
 	err error
 }
 
 func (d *Db) Query(query string) *Query {
+	d.Lock()
+	q := d.query(query)
+	q.db = d
+	return q
+}
+
+func (d *Db) query(query string) *Query {
 	stmt, remaining, err := d.Db.PrepareTransient(query)
 	if err != nil {
 		return &Query{err: err}
@@ -44,8 +55,10 @@ func (q *Query) Bind(args ...any) *Query {
 }
 
 func (q *Query) Exec() (rerr error) {
+	defer q.unlock()
+
 	if q.stmt != nil {
-		defer func() { rerr = q.stmt.Finalize() }()
+		defer func() { forwardError(q.stmt.Finalize(), &rerr) }()
 	}
 	if q.err != nil {
 		return q.err
@@ -68,34 +81,41 @@ func (q *Query) MustExec() {
 }
 
 func (q *Query) ScanSingle(results ...any) (rerr error) {
+	defer q.unlock()
+	// Scan rows
 	if q.stmt != nil {
-		defer func() { rerr = q.stmt.Finalize() }()
+		defer func() { forwardError(q.stmt.Finalize(), &rerr) }()
 	}
 	if q.err != nil {
 		return q.err
 	}
-	rowReturned, err := q.stmt.Step()
+	rows, err := q.ScanMulti()
 	if err != nil {
 		return err
 	}
-	if !rowReturned {
+
+	// Fetch the first row
+	hasResult, err := rows.Next()
+	if err != nil {
+		return err
+	}
+	if !hasResult {
 		return fmt.Errorf("did not return any rows")
 	}
 
-	for i, arg := range results {
+	// Scan its columns
-		if asString, ok := arg.(*string); ok {
+	err = rows.Scan(results...)
-			*asString = q.stmt.ColumnText(i)
+	if err != nil {
-		} else if asInt, ok := arg.(*int); ok {
+		return err
-			*asInt = q.stmt.ColumnInt(i)
-		} else if asBool, ok := arg.(*bool); ok {
-			*asBool = q.stmt.ColumnBool(i)
-		} else {
-			if reflect.TypeOf(arg).Kind() != reflect.Ptr {
-				return fmt.Errorf("unsupported column type %s at index %d (it should be a pointer)", reflect.TypeOf(arg).Name(), i)
 	}
-			name := reflect.Indirect(reflect.ValueOf(arg)).Type().Name()
+
-			return fmt.Errorf("unsupported column type *%s at index %d", name, i)
+	// Ensure there are no more rows
+	hasResult, err = rows.Next()
+	if err != nil {
+		return err
 	}
+	if hasResult {
+		return fmt.Errorf("returned more than one row")
 	}
 	return nil
 }
@@ -106,3 +126,134 @@ func (q *Query) MustScanSingle(results ...any) {
 		panic(fmt.Sprintf("error getting results: %v", err))
 	}
 }
+
+func (q *Query) unlock() {
+	if q.db != nil {
+		q.db.Unlock()
+	}
+}
+
+type Rows struct {
+	query *Query
+}
+
+func (q *Query) ScanMulti() (*Rows, error) {
+	return &Rows{
+		query: q,
+	}, nil
+}
+
+func (r *Rows) Finish() error {
+	defer r.query.unlock()
+	return r.query.stmt.Finalize()
+}
+
+func (r *Rows) MustFinish() {
+	err := r.Finish()
+	if err != nil {
+		panic(err)
+	}
+}
+
+func (r *Rows) Next() (bool, error) {
+	gotRow, err := r.query.stmt.Step()
+	if err != nil {
+		return false, err
+	}
+	return gotRow, nil
+}
+
+func (r *Rows) MustNext() bool {
+	gotRow, err := r.Next()
+	if err != nil {
+		panic(err)
+	}
+	return gotRow
+}
+
+func (r *Rows) Scan(results ...any) error {
+	for i, arg := range results {
+		err := r.scanArgument(i, arg)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (r *Rows) scanArgument(i int, arg any) error {
+	if asString, ok := arg.(*string); ok {
+		*asString = r.query.stmt.ColumnText(i)
+	} else if asInt, ok := arg.(*int); ok {
+		*asInt = r.query.stmt.ColumnInt(i)
+	} else if asBool, ok := arg.(*bool); ok {
+		*asBool = r.query.stmt.ColumnBool(i)
+	} else if reflect.TypeOf(arg).Kind() == reflect.Ptr && reflect.TypeOf(arg).Elem().Kind() == reflect.Ptr {
+		return r.handleNullableType(i, arg)
+	} else {
+		if reflect.TypeOf(arg).Kind() != reflect.Ptr {
+			return fmt.Errorf("unsupported column type %s at index %d (it should be a pointer)", reflect.TypeOf(arg).Name(), i)
+		}
+		name := reflect.Indirect(reflect.ValueOf(arg)).Type().Name()
+		return fmt.Errorf("unsupported column type *%s at index %d", name, i)
+	}
+	return nil
+}
+
+func (r *Rows) handleNullableType(i int, asPtr any) error {
+	if r.query.stmt.ColumnIsNull(i) {
+		reflect.ValueOf(asPtr).Elem().Set(reflect.Zero(reflect.TypeOf(asPtr).Elem()))
+	} else {
+		value := reflect.New(reflect.TypeOf(asPtr).Elem().Elem()).Interface()
+		err := r.scanArgument(i, value)
+		if err != nil {
+			return err
+		}
+		reflect.ValueOf(asPtr).Elem().Set(reflect.ValueOf(value))
+	}
+	return nil
+}
+
+func (r *Rows) MustScan(results ...any) {
+	err := r.Scan(results...)
+	if err != nil {
+		panic(err)
+	}
+}
+
+func (q *Query) Range(err *error) iter.Seq[*Rows] {
+	return func(yield func(*Rows) bool) {
+		// Start the scan
+		rows, terr := q.ScanMulti()
+		if terr != nil {
+			*err = terr
+			return
+		}
+
+		// Ensure we close and return any errors
+		defer func() {
+			terr := rows.Finish()
+			if terr != nil {
+				*err = terr
+			}
+		}()
+
+		// Loop over each record
+		for {
+			// Get the record
+			hasRow, terr := rows.Next()
+			if terr != nil {
+				*err = terr
+				return
+			}
+			if !hasRow {
+				return
+			}
+
+			// Pass it to the range body
+			if !yield(&Rows{query: q}) {
+				return
+			}
+		}
+	}
+}

query_test.go

@@ -25,3 +25,111 @@ func TestSimpleQueryWithArgs(t *testing.T) {
 	db.Query("select value from mytable where key = ?").Bind("foo").MustScanSingle(&value)
 	require.Equal(t, "bar", value, "bad value returned")
 }
+
+func TestQueryWithTwoRows(t *testing.T) {
+	db := openTestDb(t)
+	db.Query("insert into mytable(key, value) values ('lorem', 'ipsum')").MustExec()
+
+	rows, err := db.Query("select value from mytable").ScanMulti()
+	require.NoError(t, err)
+	defer rows.MustFinish()
+
+	require.True(t, rows.MustNext(), "expected first row")
+	var value string
+	rows.MustScan(&value)
+	require.Equal(t, "bar", value, "bad value returned")
+
+	require.True(t, rows.MustNext(), "expected second row")
+	rows.MustScan(&value)
+	require.Equal(t, "ipsum", value, "bad value returned")
+
+	require.False(t, rows.MustNext(), "expected no more rows")
+}
+
+func TestQueryWithRange(t *testing.T) {
+	db := openTestDb(t)
+	db.Query("insert into mytable(key, value) values ('lorem', 'ipsum')").MustExec()
+
+	var err error
+	index := 0
+	for row := range db.Query("select value from mytable").Range(&err) {
+		var value string
+		row.MustScan(&value)
+		if index == 0 {
+			require.Equal(t, "bar", value)
+		} else if index == 1 {
+			require.Equal(t, "ipsum", value)
+		} else {
+			require.FailNow(t, "more rows than expected")
+		}
+		index++
+	}
+	require.NoError(t, err)
+}
+
+func TestUpdateQuery(t *testing.T) {
+	db := openTestDb(t)
+	func() {
+		tx := db.MustBegin()
+		defer tx.MustRollback()
+		tx.Query("insert into mytable(key, value) values ('lorem', 'bar')").MustExec()
+		value := "ipsum"
+		key := "lorem"
+		tx.Query("update mytable set value = ? where key = ?").Bind(value, key).MustExec()
+		tx.MustCommit()
+	}()
+
+	var value string
+	db.Query("select value from mytable where key = 'lorem'").MustScanSingle(&value)
+	require.Equal(t, "ipsum", value)
+}
+
+func TestUpdateQueryWithWrongArguments(t *testing.T) {
+	db := openTestDb(t)
+	value := "ipsum"
+	err := db.Query("insert into mytable(key, value) values ('lorem', ?)").Bind(&value).Exec()
+	require.Error(t, err)
+}
+
+func TestQueryWithPointerStringArguments(t *testing.T) {
+	db := openTestDb(t)
+	var result *string
+	err := db.Query("select value from mytable where key = 'foo'").ScanSingle(&result)
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.Equal(t, "bar", *result)
+}
+
+func TestQueryWithPointerStringArgumentsCanSetToNull(t *testing.T) {
+	db := openTestDb(t)
+	db.Query("update mytable set value=NULL where key = 'foo'").MustExec()
+	myString := "some string"
+	var result *string
+	result = &myString
+	err := db.Query("select value from mytable where key = 'foo'").ScanSingle(&result)
+	require.NoError(t, err)
+	require.Nil(t, result)
+}
+
+func TestDeleteQuery(t *testing.T) {
+	db := openTestDb(t)
+	db.Query("delete from mytable where key = 'foo'").MustExec()
+
+	var count int
+	db.Query("select count(*) from mytable where key = 'foo'").MustScanSingle(&count)
+	require.Equal(t, 0, count, "expected row to be deleted")
+}
+
+func TestTransactionRollback(t *testing.T) {
+	db := openTestDb(t)
+	func() {
+		tx := db.MustBegin()
+		defer tx.MustRollback()
+		tx.Query("update mytable set value = 'ipsum' where key = 'foo'").MustExec()
+		// Intentionally not committing the transaction
+	}()
+
+	var value string
+	db.Query("select value from mytable where key = 'foo'").MustScanSingle(&value)
+	require.Equal(t, "bar", value, "expected original value after rollback")
+}

testMigrations/3_multicomment.sql

@@ -0,0 +1,3 @@
+create table multiTable(value text);
+
+insert into multiTable(value) values ('testValue');

transaction.go

@@ -7,18 +7,40 @@ type Tx struct {
 }
 
 func (d *Db) Begin() (*Tx, error) {
-	err := d.Query("BEGIN").Exec()
+	d.Lock()
+	err := d.query("BEGIN").Exec()
 	if err != nil {
 		return nil, err
 	}
 	return &Tx{db: d}, nil
 }
 
+func (d *Db) MustBegin() *Tx {
+	tx, err := d.Begin()
+	if err != nil {
+		panic(err)
+	}
+	return tx
+}
+
 func (tx *Tx) Commit() error {
+	defer tx.unlock()
 	return tx.Query("COMMIT").Exec()
 }
 
+func (tx *Tx) MustCommit() {
+	err := tx.Commit()
+	if err != nil {
+		panic(err)
+	}
+}
+
 func (tx *Tx) Rollback() error {
+	if tx.db == nil {
+		// The transaction was already commited
+		return nil
+	}
+	defer tx.unlock()
 	return tx.Query("ROLLBACK").Exec()
 }
 
@@ -29,6 +51,16 @@ func (tx *Tx) MustRollback() {
 	}
 }
 
-func (tx *Tx) Query(query string) *Query {
+func (tx *Tx) unlock() {
-	return tx.db.Query(query)
+	if tx.db != nil {
+		tx.db.Unlock()
+		tx.db = nil
+	}
+}
+
+func (tx *Tx) Query(query string) *Query {
+	if tx.db == nil {
+		panic("query was performed on a transaction after Commit or Rollback")
+	}
+	return tx.db.query(query)
 }

util.go

@@ -0,0 +1,7 @@
+package mysqlite
+
+func forwardError(from error, to *error) {
+	if from != nil {
+		*to = from
+	}
+}