Handle Microsoft Access MEMO parameters properly

Fixes alexbrainman#106

Author: alexbrainman

access_test.go

@@ -0,0 +1,71 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package odbc
+
+import (
+	"database/sql"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+
+	ole "github.com/go-ole/go-ole"
+	"github.com/go-ole/go-ole/oleutil"
+)
+
+func TestAccessMemo(t *testing.T) {
+	tmpdir, err := ioutil.TempDir("", "TestAccessMemo")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpdir)
+
+	dbfilename := filepath.Join(tmpdir, "db.mdb")
+	createAccessDB(t, dbfilename)
+
+	db, err := sql.Open("odbc", fmt.Sprintf("DRIVER={Microsoft Access Driver (*.mdb)};DBQ=%s;", dbfilename))
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	err = db.Ping()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = db.Exec("create table mytable (m memo)")
+	if err != nil {
+		t.Fatal(err)
+	}
+	for s := ""; len(s) < 1000; s += "0123456789" {
+		_, err = db.Exec("insert into mytable (m) values (?)", s)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+}
+
+func createAccessDB(t *testing.T, dbfilename string) {
+	err := ole.CoInitialize(0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer ole.CoUninitialize()
+
+	unk, err := oleutil.CreateObject("adox.catalog")
+	if err != nil {
+		t.Fatal(err)
+	}
+	cat, err := unk.QueryInterface(ole.IID_IDispatch)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = oleutil.CallMethod(cat, "create", fmt.Sprintf("provider=microsoft.jet.oledb.4.0;data source=%s;", dbfilename))
+	if err != nil {
+		t.Fatal(err)
+	}
+}

conn.go

@@ -6,17 +6,21 @@ package odbc
 
 import (
 	"database/sql/driver"
+	"strings"
 	"unsafe"
 
 	"github.com/alexbrainman/odbc/api"
 )
 
 type Conn struct {
-	h   api.SQLHDBC
-	tx  *Tx
-	bad bool
+	h                api.SQLHDBC
+	tx               *Tx
+	bad              bool
+	isMSAccessDriver bool
 }
 
+var accessDriverSubstr = strings.ToUpper(strings.Replace("DRIVER={Microsoft Access Driver", " ", "", -1))
+
 func (d *Driver) Open(dsn string) (driver.Conn, error) {
 	var out api.SQLHANDLE
 	ret := api.SQLAllocHandle(api.SQL_HANDLE_DBC, api.SQLHANDLE(d.h), &out)
@@ -34,7 +38,8 @@ func (d *Driver) Open(dsn string) (driver.Conn, error) {
 		defer releaseHandle(h)
 		return nil, NewError("SQLDriverConnect", h)
 	}
-	return &Conn{h: h}, nil
+	isAccess := strings.Contains(strings.ToUpper(strings.Replace(dsn, " ", "", -1)), accessDriverSubstr)
+	return &Conn{h: h, isMSAccessDriver: isAccess}, nil
 }
 
 func (c *Conn) Close() (err error) {

odbcstmt.go

@@ -95,7 +95,7 @@ func (s *ODBCStmt) releaseHandle() error {
 
 var testingIssue5 bool // used during tests
 
-func (s *ODBCStmt) Exec(args []driver.Value) error {
+func (s *ODBCStmt) Exec(args []driver.Value, conn *Conn) error {
 	if len(args) != len(s.Parameters) {
 		return fmt.Errorf("wrong number of arguments %d, %d expected", len(args), len(s.Parameters))
 	}
@@ -105,7 +105,7 @@ func (s *ODBCStmt) Exec(args []driver.Value) error {
 		// 2) set their (vars) values here;
 		// but rebinding parameters for every new parameter value
 		// should be efficient enough for our purpose.
-		if err := s.Parameters[i].BindValue(s.h, i, a); err != nil {
+		if err := s.Parameters[i].BindValue(s.h, i, a, conn); err != nil {
 			return err
 		}
 	}

param.go

@@ -32,7 +32,7 @@ func (p *Parameter) StoreStrLen_or_IndPtr(v api.SQLLEN) *api.SQLLEN {
 
 }
 
-func (p *Parameter) BindValue(h api.SQLHSTMT, idx int, v driver.Value) error {
+func (p *Parameter) BindValue(h api.SQLHSTMT, idx int, v driver.Value, conn *Conn) error {
 	// TODO(brainman): Reuse memory for previously bound values. If memory
 	// is reused, we, probably, do not need to call SQLBindParameter either.
 	var ctype, sqltype, decimal api.SQLSMALLINT
@@ -64,15 +64,21 @@ func (p *Parameter) BindValue(h api.SQLHSTMT, idx int, v driver.Value) error {
 		l *= 2 // every char takes 2 bytes
 		buflen = api.SQLLEN(l)
 		plen = p.StoreStrLen_or_IndPtr(buflen)
-		switch {
-		case size >= 4000:
+		if !conn.isMSAccessDriver {
+			switch {
+			case size >= 4000:
+				sqltype = api.SQL_WLONGVARCHAR
+			case p.isDescribed:
+				sqltype = p.SQLType
+			case size <= 1:
+				sqltype = api.SQL_WVARCHAR
+			default:
+				sqltype = api.SQL_WCHAR
+			}
+		} else {
+			// MS Acess requires SQL_WLONGVARCHAR for MEMO.
+			// https://docs.microsoft.com/en-us/sql/odbc/microsoft/microsoft-access-data-types
 			sqltype = api.SQL_WLONGVARCHAR
-		case p.isDescribed:
-			sqltype = p.SQLType
-		case size <= 1:
-			sqltype = api.SQL_WVARCHAR
-		default:
-			sqltype = api.SQL_WCHAR
 		}
 	case int64:
 		if -0x80000000 < d && d < 0x7fffffff {

stmt.go

@@ -61,7 +61,7 @@ func (s *Stmt) Exec(args []driver.Value) (driver.Result, error) {
 		}
 		s.os = os
 	}
-	err := s.os.Exec(args)
+	err := s.os.Exec(args, s.c)
 	if err != nil {
 		return nil, err
 	}
@@ -88,7 +88,7 @@ func (s *Stmt) Query(args []driver.Value) (driver.Rows, error) {
 		}
 		s.os = os
 	}
-	err := s.os.Exec(args)
+	err := s.os.Exec(args, s.c)
 	if err != nil {
 		return nil, err
 	}