1 files changed, 50 insertions, 8 deletions
diff --git a/src/pkg/database/sql/convert.go b/src/pkg/database/sql/convert.go
index bfcb03ccf8..964dc18485 100644
--- a/src/pkg/database/sql/convert.go
+++ b/src/pkg/database/sql/convert.go
@@ -14,19 +14,61 @@ import (
 	"strconv"
 )
 
-// subsetTypeArgs takes a slice of arguments from callers of the sql
-// package and converts them into a slice of the driver package's
-// "subset types".
-func subsetTypeArgs(args []interface{}) ([]driver.Value, error) {
-	out := make([]driver.Value, len(args))
+// driverArgs converts arguments from callers of Stmt.Exec and
+// Stmt.Query into driver Values.
+//
+// The statement si may be nil, if no statement is available.
+func driverArgs(si driver.Stmt, args []interface{}) ([]driver.Value, error) {
+	dargs := make([]driver.Value, len(args))
+	cc, ok := si.(driver.ColumnConverter)
+
+	// Normal path, for a driver.Stmt that is not a ColumnConverter.
+	if !ok {
+		for n, arg := range args {
+			var err error
+			dargs[n], err = driver.DefaultParameterConverter.ConvertValue(arg)
+			if err != nil {
+				return nil, fmt.Errorf("sql: converting Exec argument #%d's type: %v", n, err)
+			}
+		}
+		return dargs, nil
+	}
+
+	// Let the Stmt convert its own arguments.
 	for n, arg := range args {
+		// First, see if the value itself knows how to convert
+		// itself to a driver type.  For example, a NullString
+		// struct changing into a string or nil.
+		if svi, ok := arg.(driver.Valuer); ok {
+			sv, err := svi.Value()
+			if err != nil {
+				return nil, fmt.Errorf("sql: argument index %d from Value: %v", n, err)
+			}
+			if !driver.IsValue(sv) {
+				return nil, fmt.Errorf("sql: argument index %d: non-subset type %T returned from Value", n, sv)
+			}
+			arg = sv
+		}
+
+		// Second, ask the column to sanity check itself. For
+		// example, drivers might use this to make sure that
+		// an int64 values being inserted into a 16-bit
+		// integer field is in range (before getting
+		// truncated), or that a nil can't go into a NOT NULL
+		// column before going across the network to get the
+		// same error.
 		var err error
-		out[n], err = driver.DefaultParameterConverter.ConvertValue(arg)
+		dargs[n], err = cc.ColumnConverter(n).ConvertValue(arg)
 		if err != nil {
-			return nil, fmt.Errorf("sql: converting argument #%d's type: %v", n+1, err)
+			return nil, fmt.Errorf("sql: converting argument #%d's type: %v", n, err)
+		}
+		if !driver.IsValue(dargs[n]) {
+			return nil, fmt.Errorf("sql: driver ColumnConverter error converted %T to unsupported type %T",
+				arg, dargs[n])
 		}
 	}
-	return out, nil
+
+	return dargs, nil
 }
 
 // convertAssign copies to dest the value in src, converting it if possible.