Allow multi-statement migration scripts

database.go

@@ -2,12 +2,14 @@ package mysqlite
 
 import (
 	"fmt"
+	"sync"
 	"zombiezen.com/go/sqlite"
 )
 
 // Db holds a connection to a SQLite database.
 type Db struct {
-	Db *sqlite.Conn
+	Db   *sqlite.Conn
+	lock sync.Mutex
 }
 
 // OpenDb opens a new connection to a SQLite database.
@@ -35,3 +37,11 @@ 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

@@ -50,7 +50,7 @@ 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
 		}
@@ -61,21 +61,29 @@ 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()
-	if err != nil {
-		return fmt.Errorf("error performing migration: %v", err)
-	}
+	for _, statement := range statements {
+		statement = strings.TrimSpace(statement)
+		err = tx.Query(statement).Exec()
+		if err != nil {
+			return fmt.Errorf("error performing migration: %v", err)
+		}
+
+		err = tx.Query(fmt.Sprintf("PRAGMA user_version = %d", targetVersion)).Exec()
+		if err != nil {
+			return fmt.Errorf("error updating version: %v", err)
+		}
 
-	err = tx.Query(fmt.Sprintf("PRAGMA user_version = %d", targetVersion)).Exec()
-	if err != nil {
-		return fmt.Errorf("error updating version: %v", err)
 	}
 
 	err = tx.Commit()

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
-	err  error
+	// 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}
@@ -44,6 +55,8 @@ 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() }()
 	}
@@ -68,27 +81,104 @@ 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() }()
 	}
 	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")
 	}
 
+	// Scan its columns
+	err = rows.Scan(results...)
+	if err != nil {
+		return err
+	}
+
+	// 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
+}
+
+func (q *Query) MustScanSingle(results ...any) {
+	err := q.ScanSingle(results...)
+	if err != nil {
+		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 {
 		if asString, ok := arg.(*string); ok {
-			*asString = q.stmt.ColumnText(i)
+			*asString = r.query.stmt.ColumnText(i)
 		} else if asInt, ok := arg.(*int); ok {
-			*asInt = q.stmt.ColumnInt(i)
+			*asInt = r.query.stmt.ColumnInt(i)
 		} else if asBool, ok := arg.(*bool); ok {
-			*asBool = q.stmt.ColumnBool(i)
+			*asBool = r.query.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)
@@ -100,9 +190,46 @@ func (q *Query) ScanSingle(results ...any) (rerr error) {
 	return nil
 }
 
-func (q *Query) MustScanSingle(results ...any) {
-	err := q.ScanSingle(results...)
+func (r *Rows) MustScan(results ...any) {
+	err := r.Scan(results...)
 	if err != nil {
-		panic(fmt.Sprintf("error getting results: %v", err))
+		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 +25,44 @@ 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)
+}

testMigrations/3_multicomment.sql

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

transaction.go

@@ -7,7 +7,8 @@ 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
 	}
@@ -15,10 +16,16 @@ func (d *Db) Begin() (*Tx, error) {
 }
 
 func (tx *Tx) Commit() error {
+	defer tx.unlock()
 	return tx.Query("COMMIT").Exec()
 }
 
 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 +36,16 @@ func (tx *Tx) MustRollback() {
 	}
 }
 
-func (tx *Tx) Query(query string) *Query {
-	return tx.db.Query(query)
+func (tx *Tx) unlock() {
+	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)
 }