sql: implement database/sql/driver API, fixes src-d#87 (src-d#108)

Author: smola

engine.go

@@ -1,17 +1,55 @@
 package gitql
 
 import (
+	gosql "database/sql"
+	"database/sql/driver"
+	"errors"
+	"fmt"
+
 	"github.com/gitql/gitql/sql"
 	"github.com/gitql/gitql/sql/analyzer"
 	"github.com/gitql/gitql/sql/expression"
 	"github.com/gitql/gitql/sql/parse"
 )
 
+var (
+	ErrNotSupported = errors.New("feature not supported yet")
+)
+
+const (
+	DriverName = "gitql"
+)
+
+func init() {
+	gosql.Register(DriverName, defaultDriver)
+}
+
+type drv struct{}
+
+var defaultDriver = &drv{}
+
+func (d *drv) Open(name string) (driver.Conn, error) {
+	if name != "" {
+		return nil, fmt.Errorf("data source not found: %s", name)
+	}
+
+	e := DefaultEngine
+	return &session{Engine: e}, nil
+}
+
+// DefaultEngine is the default Engine instance, used when opening a connection
+// to gitql:// when using database/sql.
+var DefaultEngine = New()
+
+// Engine is a SQL engine.
+// It implements the standard database/sql/driver/Driver interface, so it can
+// be registered as a database/sql driver.
 type Engine struct {
 	Catalog  *sql.Catalog
 	Analyzer *analyzer.Analyzer
 }
 
+// New creates a new Engine.
 func New() *Engine {
 	c := sql.NewCatalog()
 	err := expression.RegisterDefaults(c)
@@ -23,11 +61,15 @@ func New() *Engine {
 	return &Engine{c, a}
 }
 
-func (e *Engine) AddDatabase(db sql.Database) {
-	e.Catalog.Databases = append(e.Catalog.Databases, db)
-	e.Analyzer.CurrentDatabase = db.Name()
+// Open creates a new session for the engine and returns
+// it as a driver.Conn.
+//
+// Name parameter is ignored.
+func (e *Engine) Open(name string) (driver.Conn, error) {
+	return &session{Engine: e}, nil
 }
 
+// Query executes a query without attaching to any session.
 func (e *Engine) Query(query string) (sql.Schema, sql.RowIter, error) {
 	parsed, err := parse.Parse(query)
 	if err != nil {
@@ -46,3 +88,134 @@ func (e *Engine) Query(query string) (sql.Schema, sql.RowIter, error) {
 
 	return analyzed.Schema(), iter, nil
 }
+
+func (e *Engine) AddDatabase(db sql.Database) {
+	e.Catalog.Databases = append(e.Catalog.Databases, db)
+	e.Analyzer.CurrentDatabase = db.Name()
+}
+
+// Session represents a SQL session.
+// It implements the standard database/sql/driver/Conn interface.
+type session struct {
+	*Engine
+	closed bool
+	//TODO: Current database
+}
+
+// Prepare returns a prepared statement, bound to this connection.
+// Placeholders are not supported yet.
+func (s *session) Prepare(query string) (driver.Stmt, error) {
+	if err := s.checkOpen(); err != nil {
+		return nil, err
+	}
+
+	return &stmt{session: s, query: query}, nil
+}
+
+// Close closes the session.
+func (s *session) Close() error {
+	if err := s.checkOpen(); err != nil {
+		return err
+	}
+
+	s.closed = true
+	return nil
+}
+
+// Begin starts and returns a new transaction.
+func (s *session) Begin() (driver.Tx, error) {
+	return nil, fmt.Errorf("transactions not supported")
+}
+
+func (s *session) checkOpen() error {
+	if s.closed {
+		return driver.ErrBadConn
+	}
+
+	return nil
+}
+
+type stmt struct {
+	*session
+	query  string
+	closed bool
+}
+
+// Close closes the statement.
+func (s *stmt) Close() error {
+	if err := s.checkOpen(); err != nil {
+		return err
+	}
+
+	s.closed = true
+	return nil
+}
+
+// NumInput returns the number of placeholder parameters.
+// Always returns -1 since placeholders are not supported yet.
+func (s *stmt) NumInput() int {
+	return -1
+}
+
+// Exec executes a query that doesn't return rows, such as an INSERT or UPDATE.
+func (s *stmt) Exec(args []driver.Value) (driver.Result, error) {
+	return nil, ErrNotSupported
+}
+
+// Query executes a query that may return rows, such as a SELECT.
+func (s *stmt) Query(args []driver.Value) (driver.Rows, error) {
+	if len(args) > 0 {
+		return nil, ErrNotSupported
+	}
+
+	schema, iter, err := s.session.Engine.Query(s.query)
+	if err != nil {
+		return nil, err
+	}
+
+	return &rows{schema: schema, iter: iter}, nil
+}
+
+func (s *stmt) checkOpen() error {
+	if s.closed {
+		return driver.ErrBadConn
+	}
+
+	return nil
+}
+
+type rows struct {
+	schema sql.Schema
+	iter   sql.RowIter
+}
+
+// Columns returns the names of the columns.
+func (rs *rows) Columns() []string {
+	c := make([]string, len(rs.schema))
+	for i := 0; i < len(rs.schema); i++ {
+		c[i] = rs.schema[i].Name
+	}
+
+	return c
+}
+
+// Close closes the rows iterator.
+func (rs *rows) Close() error {
+	return rs.iter.Close()
+}
+
+// Next populates the given array with the next row values.
+// Returns io.EOF when there are no more values.
+func (rs *rows) Next(dest []driver.Value) error {
+	r, err := rs.iter.Next()
+	if err != nil {
+		return err
+	}
+
+	for i := range dest {
+		f := rs.schema[i]
+		dest[i] = f.Type.Native(r[i])
+	}
+
+	return nil
+}

engine_test.go

@@ -1,7 +1,7 @@
 package gitql_test
 
 import (
-	"io"
+	gosql "database/sql"
 	"testing"
 
 	"github.com/gitql/gitql"
@@ -11,77 +11,83 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+const (
+	driverName = "engine_tests"
+)
+
 func TestEngine_Query(t *testing.T) {
 	e := newEngine(t)
+	gosql.Register(driverName, e)
 	testQuery(t, e,
 		"SELECT i FROM mytable;",
-		[]sql.Row{
-			sql.NewRow(int64(1)),
-			sql.NewRow(int64(2)),
-			sql.NewRow(int64(3)),
-		},
+		[][]interface{}{{int64(1)}, {int64(2)}, {int64(3)}},
 	)
 
 	testQuery(t, e,
 		"SELECT i FROM mytable WHERE i = 2;",
-		[]sql.Row{
-			sql.NewRow(int64(2)),
-		},
+		[][]interface{}{{int64(2)}},
 	)
 
 	testQuery(t, e,
 		"SELECT i FROM mytable ORDER BY i DESC;",
-		[]sql.Row{
-			sql.NewRow(int64(3)),
-			sql.NewRow(int64(2)),
-			sql.NewRow(int64(1)),
-		},
+		[][]interface{}{{int64(3)}, {int64(2)}, {int64(1)}},
 	)
 
 	testQuery(t, e,
 		"SELECT i FROM mytable WHERE s = 'a' ORDER BY i DESC;",
-		[]sql.Row{
-			sql.NewRow(int64(1)),
-		},
+		[][]interface{}{{int64(1)}},
 	)
 
 	testQuery(t, e,
 		"SELECT i FROM mytable WHERE s = 'a' ORDER BY i DESC LIMIT 1;",
-		[]sql.Row{
-			sql.NewRow(int64(1)),
-		},
+		[][]interface{}{{int64(1)}},
 	)
 
 	testQuery(t, e,
 		"SELECT COUNT(*) FROM mytable;",
-		[]sql.Row{
-			sql.NewRow(int32(3)),
-		},
+		[][]interface{}{{int64(3)}},
 	)
 }
 
-func testQuery(t *testing.T, e *gitql.Engine, q string, r []sql.Row) {
+func testQuery(t *testing.T, e *gitql.Engine, q string, r [][]interface{}) {
 	assert := require.New(t)
 
-	schema, iter, err := e.Query(q)
-	assert.Nil(err)
-	assert.NotNil(iter)
-	assert.NotNil(schema)
+	db, err := gosql.Open(driverName, "")
+	assert.NoError(err)
+	defer func() { assert.NoError(db.Close()) }()
+
+	res, err := db.Query(q)
+	assert.NoError(err)
+	defer func() { assert.NoError(res.Close()) }()
 
-	results := []sql.Row{}
+	cols, err := res.Columns()
+	assert.NoError(err)
+	assert.Equal(len(r[0]), len(cols))
+
+	i := 0
 	for {
-		el, err := iter.Next()
-		if err == io.EOF {
+		if !res.Next() {
 			break
 		}
-		if err != nil {
-			assert.Fail("returned err distinct of io.EOF: %q", err)
+
+		expectedRow := r[i]
+		i++
+
+		row := make([]interface{}, len(expectedRow))
+		for i := range row {
+			i64 := int64(0)
+			row[i] = &i64
+		}
+
+		assert.NoError(res.Scan(row...))
+		for i := range row {
+			row[i] = *(row[i].(*int64))
 		}
-		results = append(results, el)
+
+		assert.Equal(expectedRow, row)
 	}
 
-	assert.Len(results, len(r))
-	assert.Equal(results, r)
+	assert.Equal(len(r), i)
 }
 
 func newEngine(t *testing.T) *gitql.Engine {