database/sql: ensure Stmts are correctly closed.

To make sure that there is no resource leak,
I suggest to fix the 'fakedb' driver such as it fails when any
Stmt is not closed.
First, add a check in fakeConn.Close().
Then, fix all missing Stmt.Close()/Rows.Close().
I am not sure that the strategy choose in fakeConn.Prepare/prepare* is ok.
The weak point in this patch is the change in Tx.Query:
  - Tests pass without this change,
  - I found it by manually analyzing the code,
  - I just try to make Tx.Query look like DB.Query.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5759050

1 files changed, 5 insertions, 3 deletions

diff --git a/src/pkg/database/sql/sql.go b/src/pkg/database/sql/sql.go
index c00425d8fa..51a357b37d 100644
--- a/src/pkg/database/sql/sql.go
+++ b/src/pkg/database/sql/sql.go
@@ -612,9 +612,11 @@ func (tx *Tx) Query(query string, args ...interface{}) (*Rows, error) {
 		return nil, err
 	}
 	rows, err := stmt.Query(args...)
-	if err == nil {
-		rows.closeStmt = stmt
+	if err != nil {
+		stmt.Close()
+		return nil, err
 	}
+	rows.closeStmt = stmt
 	return rows, err
 }
 
@@ -1020,7 +1022,7 @@ func (r *Row) Scan(dest ...interface{}) error {
 	}
 
 	// TODO(bradfitz): for now we need to defensively clone all
-	// []byte that the driver returned (not permitting 
+	// []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