Add support for ScanType in ColumnType.

The ColumnType.ScanType() function returns information about the type
which is expected to be passed to the Rows.Scan() function for the
corresponding column.  Without this commit go-txdb will claim
everything should be an interface{} which, while not exactly wrong, is
not particularly helpful.

I've also added a quick test to the PostgreSQL suite since that's where
I'm thinking about using this library, but AFAIK this should also be
effective for MySQL.

db.go

@@ -57,6 +57,7 @@ import (
 	"database/sql/driver"
 	"fmt"
 	"io"
+	"reflect"
 	"sync"
 )
 
@@ -401,6 +402,10 @@ func (rs *rowSets) ColumnTypeDatabaseTypeName(index int) string {
 	return rs.sets[rs.pos].ColumnTypeDatabaseTypeName(index)
 }
 
+func (rs *rowSets) ColumnTypeScanType(index int) reflect.Type {
+	return rs.sets[rs.pos].colTypes[index].ScanType()
+}
+
 func (rs *rowSets) Close() error {
 	return nil
 }

postgresql_test.go

@@ -2,8 +2,37 @@
 
 package txdb
 
-import _ "github.com/lib/pq"
+import (
+	"database/sql"
+	"reflect"
+	"testing"
+
+	_ "github.com/lib/pq"
+)
 
 func init() {
 	Register("psql_txdb", "postgres", "postgres://postgres@localhost/txdb_test?sslmode=disable")
 }
+
+func TestRowsScanTypeTables(t *testing.T) {
+	db, err := sql.Open("psql_txdb", "scantype")
+	if err != nil {
+		t.Fatalf("psql: failed to open a postgres connection, have you run 'make test'? err: %s", err)
+	}
+	defer db.Close()
+
+	rows, err := db.Query("SELECT 1")
+	if err != nil {
+		t.Fatalf("psql: unable to execute trivial query: %v", err)
+	}
+
+	colTypes, err := rows.ColumnTypes()
+	if err != nil {
+		t.Fatalf("psql: unable to retrieve column types: %v", err)
+	}
+
+	int32Type := reflect.TypeOf(int32(0))
+	if colTypes[0].ScanType() != int32Type {
+		t.Fatalf("psql: column scan type is %s, but should be %s", colTypes[0].ScanType().String(), int32Type.String())
+	}
+}