database/sql{,driver}: add ErrBadConn

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5785043

1 files changed, 11 insertions, 0 deletions

diff --git a/src/pkg/database/sql/driver/driver.go b/src/pkg/database/sql/driver/driver.go
index 7f986b80f2..2f5280db81 100644
--- a/src/pkg/database/sql/driver/driver.go
+++ b/src/pkg/database/sql/driver/driver.go
@@ -43,6 +43,17 @@ type Driver interface {
 // documented.
 var ErrSkip = errors.New("driver: skip fast-path; continue as if unimplemented")
 
+// ErrBadConn should be returned by a driver to signal to the sql
+// package that a driver.Conn is in a bad state (such as the server
+// having earlier closed the connection) and the sql package should
+// retry on a new connection.
+//
+// To prevent duplicate operations, ErrBadConn should NOT be returned
+// if there's a possibility that the database server might have
+// performed the operation. Even if the server sends back an error,
+// you shouldn't return ErrBadConn.
+var ErrBadConn = errors.New("driver: bad connection")
+
 // Execer is an optional interface that may be implemented by a Conn.
 //
 // If a Conn does not implement Execer, the db package's DB.Exec will