database/sql: support returning query database types

Creates a ColumnType structure that can be extended in to future.
Allow drivers to implement what makes sense for the database.

Fixes #16652

Change-Id: Ieb1fd64eac1460107b1d3474eba5201fa300a4ec
Reviewed-on: https://go-review.googlesource.com/29961
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

1 files changed, 50 insertions, 9 deletions

diff --git a/src/database/sql/fakedb_test.go b/src/database/sql/fakedb_test.go
index 07f50196a5..c42f23208f 100644
--- a/src/database/sql/fakedb_test.go
+++ b/src/database/sql/fakedb_test.go
@@ -11,6 +11,7 @@ import (
 	"fmt"
 	"io"
 	"log"
+	"reflect"
 	"sort"
 	"strconv"
 	"strings"
@@ -405,6 +406,7 @@ func (c *fakeConn) prepareSelect(stmt *fakeStmt, parts []string) (*fakeStmt, err
 		return nil, errf("invalid SELECT syntax with %d parts; want 3", len(parts))
 	}
 	stmt.table = parts[0]
+
 	stmt.colName = strings.Split(parts[1], ",")
 	for n, colspec := range strings.Split(parts[2], ",") {
 		if colspec == "" {
@@ -725,6 +727,7 @@ func (s *fakeStmt) QueryContext(ctx context.Context, args []driver.NamedValue) (
 
 	setMRows := make([][]*row, 0, 1)
 	setColumns := make([][]string, 0, 1)
+	setColType := make([][]string, 0, 1)
 
 	for {
 		db.mu.Lock()
@@ -794,10 +797,16 @@ func (s *fakeStmt) QueryContext(ctx context.Context, args []driver.NamedValue) (
 			mrows = append(mrows, mrow)
 		}
 
+		var colType []string
+		for _, column := range s.colName {
+			colType = append(colType, t.coltype[t.columnIndex(column)])
+		}
+
 		t.mu.Unlock()
 
 		setMRows = append(setMRows, mrows)
 		setColumns = append(setColumns, s.colName)
+		setColType = append(setColType, colType)
 
 		if s.next == nil {
 			break
@@ -806,10 +815,11 @@ func (s *fakeStmt) QueryContext(ctx context.Context, args []driver.NamedValue) (
 	}
 
 	cursor := &rowsCursor{
-		posRow: -1,
-		rows:   setMRows,
-		cols:   setColumns,
-		errPos: -1,
+		posRow:  -1,
+		rows:    setMRows,
+		cols:    setColumns,
+		colType: setColType,
+		errPos:  -1,
 	}
 	return cursor, nil
 }
@@ -844,11 +854,12 @@ func (tx *fakeTx) Rollback() error {
 }
 
 type rowsCursor struct {
-	cols   [][]string
-	posSet int
-	posRow int
-	rows   [][]*row
-	closed bool
+	cols    [][]string
+	colType [][]string
+	posSet  int
+	posRow  int
+	rows    [][]*row
+	closed  bool
 
 	// errPos and err are for making Next return early with error.
 	errPos int
@@ -874,6 +885,10 @@ func (rc *rowsCursor) Columns() []string {
 	return rc.cols[rc.posSet]
 }
 
+func (rc *rowsCursor) ColumnTypeScanType(index int) reflect.Type {
+	return colTypeToReflectType(rc.colType[rc.posSet][index])
+}
+
 var rowsCursorNextHook func(dest []driver.Value) error
 
 func (rc *rowsCursor) Next(dest []driver.Value) error {
@@ -980,3 +995,29 @@ func converterForType(typ string) driver.ValueConverter {
 	}
 	panic("invalid fakedb column type of " + typ)
 }
+
+func colTypeToReflectType(typ string) reflect.Type {
+	switch typ {
+	case "bool":
+		return reflect.TypeOf(false)
+	case "nullbool":
+		return reflect.TypeOf(NullBool{})
+	case "int32":
+		return reflect.TypeOf(int32(0))
+	case "string":
+		return reflect.TypeOf("")
+	case "nullstring":
+		return reflect.TypeOf(NullString{})
+	case "int64":
+		return reflect.TypeOf(int64(0))
+	case "nullint64":
+		return reflect.TypeOf(NullInt64{})
+	case "float64":
+		return reflect.TypeOf(float64(0))
+	case "nullfloat64":
+		return reflect.TypeOf(NullFloat64{})
+	case "datetime":
+		return reflect.TypeOf(time.Time{})
+	}
+	panic("invalid fakedb column type of " + typ)
+}