Don’t ignore errors from the data layer

If the data layer encountered an error when committing a transaction, then the error was ignored. Now all errors from the data layer which occur when cancelling or committing a transaction are passed to the end-user and displayed accordingly.

db/executor.go

@@ -144,13 +144,21 @@ func (e *executor) execute(ctx context.Context, ast *sql.Query) {
 				continue
 			case *sql.CancelStatement:
 				err, buf = e.cancel(buf, err, e.send)
+				if err != nil {
+					clear()
+				} else {
+					clear()
+				}
 				trc.Finish()
-				clear()
 				continue
 			case *sql.CommitStatement:
 				err, buf = e.commit(buf, err, e.send)
+				if err != nil {
+					clear()
+				} else {
+					flush()
+				}
 				trc.Finish()
-				flush()
 				continue
 			}
 
@@ -339,9 +347,9 @@ func (e *executor) operate(ctx context.Context, stm sql.Statement) (res []interf
 
 	}
 
-	// If this is a local transaction for only the
-	// current statement, then commit or cancel
-	// depending on the result error.
+	// If the context is already closed or errord,
+	// then ignore this result, clear all queued
+	// changes, and reset the transaction.
 
 	select {
 
@@ -353,15 +361,44 @@ func (e *executor) operate(ctx context.Context, stm sql.Statement) (res []interf
 
 	default:
 
+		// If this is a local transaction for only the
+		// current statement, then commit or cancel
+		// depending on the result error.
+
 		if loc && e.dbo.Closed() == false {
-			if !trw || err != nil {
+
+			// As this is a local transaction then
+			// make sure we reset the transaction
+			// context.
+
+			defer e.dbo.Reset()
+
+			// If there was an error with the query
+			// then clear the queued changes and
+			// return immediately.
+
+			if err != nil {
 				e.dbo.Cancel()
-				e.dbo.Reset()
 				clear()
+				return
+			}
+
+			// Otherwise check if this is a read or
+			// a write transaction, and attempt to
+			// Cancel or Commit, returning any errors.
+
+			if !trw {
+				if err = e.dbo.Cancel(); err != nil {
+					clear()
+				} else {
+					clear()
+				}
 			} else {
-				e.dbo.Commit()
-				e.dbo.Reset()
-				flush()
+				if err = e.dbo.Commit(); err != nil {
+					clear()
+				} else {
+					flush()
+				}
 			}
 		}
 
@@ -380,18 +417,18 @@ func (e *executor) begin(rw bool) (err error) {
 
 func (e *executor) cancel(buf []*Response, err error, chn chan<- *Response) (error, []*Response) {
 
-	defer func() {
-		e.dbo.Reset()
-	}()
+	defer e.dbo.Reset()
 
 	if e.dbo.TX == nil {
 		return nil, buf
 	}
 
-	e.dbo.Cancel()
+	err = e.dbo.Cancel()
 
 	for _, v := range buf {
 		v.Status = "ERR"
+		v.Result = []interface{}{}
+		v.Detail = "Transaction cancelled"
 		chn <- v
 	}
 
@@ -400,29 +437,29 @@ func (e *executor) cancel(buf []*Response, err error, chn chan<- *Response) (err
 		buf = buf[:len(buf)-1]
 	}
 
-	return nil, buf
+	return err, buf
 
 }
 
 func (e *executor) commit(buf []*Response, err error, chn chan<- *Response) (error, []*Response) {
 
-	defer func() {
-		e.dbo.Reset()
-	}()
+	defer e.dbo.Reset()
 
 	if e.dbo.TX == nil {
 		return nil, buf
 	}
 
 	if err != nil {
-		e.dbo.Cancel()
+		err = e.dbo.Cancel()
 	} else {
-		e.dbo.Commit()
+		err = e.dbo.Commit()
 	}
 
 	for _, v := range buf {
 		if err != nil {
 			v.Status = "ERR"
+			v.Result = []interface{}{}
+			v.Detail = "Transaction failed: " + err.Error()
 		}
 		chn <- v
 	}
@@ -432,7 +469,7 @@ func (e *executor) commit(buf []*Response, err error, chn chan<- *Response) (err
 		buf = buf[:len(buf)-1]
 	}
 
-	return nil, buf
+	return err, buf
 
 }