database/sql: convert SQL null values to []byte as nil.

Also allow string values to scan into []byte.
Fixes #2788.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5577054

diff --git a/src/pkg/database/sql/convert.go b/src/pkg/database/sql/convert.go
index 9835e38de7e24c2e806640f4ec9b26d8857c7d28..e80420e5bb3aa1726f2f031161e18865a16ca123 100644 (file)
--- a/src/pkg/database/sql/convert.go
+++ b/src/pkg/database/sql/convert.go
@@ -40,6 +40,9 @@ func convertAssign(dest, src interface{}) error {
                case *string:
                        *d = s
                        return nil
+               case *[]byte:
+                       *d = []byte(s)
+                       return nil
                }
        case []byte:
                switch d := dest.(type) {
@@ -50,6 +53,12 @@ func convertAssign(dest, src interface{}) error {
                        *d = s
                        return nil
                }
+       case nil:
+               switch d := dest.(type) {
+               case *[]byte:
+                       *d = nil
+                       return nil
+               }
        }
 
        var sv reflect.Value

diff --git a/src/pkg/database/sql/sql.go b/src/pkg/database/sql/sql.go
index 7e226b17dc62f52ed7f3c6e30dde2d85700084ad..34a76521050d7600b8f401839a761041eed10b71 100644 (file)
--- a/src/pkg/database/sql/sql.go
+++ b/src/pkg/database/sql/sql.go
@@ -904,6 +904,12 @@ func (rs *Rows) Scan(dest ...interface{}) error {
                if !ok {
                        continue
                }
+               if *b == nil {
+                       // If the []byte is now nil (for a NULL value),
+                       // don't fall through to below which would
+                       // turn it into a non-nil 0-length byte slice
+                       continue
+               }
                if _, ok = dp.(*RawBytes); ok {
                        continue
                }
@@ -945,17 +951,10 @@ func (r *Row) Scan(dest ...interface{}) error {
        if r.err != nil {
                return r.err
        }
-       defer r.rows.Close()
-       if !r.rows.Next() {
-               return ErrNoRows
-       }
-       err := r.rows.Scan(dest...)
-       if err != nil {
-               return err
-       }
 
        // TODO(bradfitz): for now we need to defensively clone all
-       // []byte that the driver returned, since we're about to close
+       // []byte that the driver returned (not permitting 
+       // *RawBytes in Rows.Scan), since we're about to close
        // the Rows in our defer, when we return from this function.
        // the contract with the driver.Next(...) interface is that it
        // can return slices into read-only temporary memory that's
@@ -970,14 +969,17 @@ func (r *Row) Scan(dest ...interface{}) error {
                if _, ok := dp.(*RawBytes); ok {
                        return errors.New("sql: RawBytes isn't allowed on Row.Scan")
                }
-               b, ok := dp.(*[]byte)
-               if !ok {
-                       continue
-               }
-               clone := make([]byte, len(*b))
-               copy(clone, *b)
-               *b = clone
        }
+
+       defer r.rows.Close()
+       if !r.rows.Next() {
+               return ErrNoRows
+       }
+       err := r.rows.Scan(dest...)
+       if err != nil {
+               return err
+       }
+
        return nil
 }
 

diff --git a/src/pkg/database/sql/sql_test.go b/src/pkg/database/sql/sql_test.go
index 08db6d38ff87945acbbacb7683eee40edece8c5e..c5cadad84999a18c5b5d48d971352d161652796e 100644 (file)
--- a/src/pkg/database/sql/sql_test.go
+++ b/src/pkg/database/sql/sql_test.go
@@ -358,6 +358,34 @@ func TestIssue2542Deadlock(t *testing.T) {
        }
 }
 
+// Tests fix for issue 2788, that we bind nil to a []byte if the
+// value in the column is sql null
+func TestNullByteSlice(t *testing.T) {
+       db := newTestDB(t, "")
+       defer closeDB(t, db)
+       exec(t, db, "CREATE|t|id=int32,name=nullstring")
+       exec(t, db, "INSERT|t|id=10,name=?", nil)
+
+       var name []byte
+
+       err := db.QueryRow("SELECT|t|name|id=?", 10).Scan(&name)
+       if err != nil {
+               t.Fatal(err)
+       }
+       if name != nil {
+               t.Fatalf("name []byte should be nil for null column value, got: %#v", name)
+       }
+
+       exec(t, db, "INSERT|t|id=11,name=?", "bob")
+       err = db.QueryRow("SELECT|t|name|id=?", 11).Scan(&name)
+       if err != nil {
+               t.Fatal(err)
+       }
+       if string(name) != "bob" {
+               t.Fatalf("name []byte should be bob, got: %q", string(name))
+       }
+}
+
 func TestQueryRowClosingStmt(t *testing.T) {
        db := newTestDB(t, "people")
        defer closeDB(t, db)