server: support decoding prepared string args to character_set_client (#30723)

server/conn.go

@@ -191,6 +191,7 @@ type clientConn struct {
 	authPlugin    string            // default authentication plugin
 	isUnixSocket  bool              // connection is Unix Socket file
 	rsEncoder     *resultEncoder    // rsEncoder is used to encode the string result to different charsets.
+	inputDecoder  *inputDecoder     // inputDecoder is used to decode the different charsets of incoming strings to utf-8.
 	socketCredUID uint32            // UID from the other end of the Unix Socket
 	// mu is used for cancelling the execution of current transaction.
 	mu struct {
@@ -964,6 +965,15 @@ func (cc *clientConn) initResultEncoder(ctx context.Context) {
 	cc.rsEncoder = newResultEncoder(chs)
 }
 
+func (cc *clientConn) initInputEncoder(ctx context.Context) {
+	chs, err := variable.GetSessionOrGlobalSystemVar(cc.ctx.GetSessionVars(), variable.CharacterSetClient)
+	if err != nil {
+		chs = ""
+		logutil.Logger(ctx).Warn("get character_set_client system variable failed", zap.Error(err))
+	}
+	cc.inputDecoder = newInputDecoder(chs)
+}
+
 // initConnect runs the initConnect SQL statement if it has been specified.
 // The semantics are MySQL compatible.
 func (cc *clientConn) initConnect(ctx context.Context) error {

server/conn_stmt.go

@@ -46,6 +46,7 @@ import (
 
 	"github.com/pingcap/errors"
 	"github.com/pingcap/tidb/kv"
+	"github.com/pingcap/tidb/parser/charset"
 	"github.com/pingcap/tidb/parser/mysql"
 	"github.com/pingcap/tidb/parser/terror"
 	plannercore "github.com/pingcap/tidb/planner/core"
@@ -167,6 +168,8 @@ func (cc *clientConn) handleStmtExecute(ctx context.Context, data []byte) (err e
 		paramTypes  []byte
 		paramValues []byte
 	)
+	cc.initInputEncoder(ctx)
+	defer cc.inputDecoder.clean()
 	numParams := stmt.NumParams()
 	args := make([]types.Datum, numParams)
 	if numParams > 0 {
@@ -194,7 +197,7 @@ func (cc *clientConn) handleStmtExecute(ctx context.Context, data []byte) (err e
 			paramValues = data[pos+1:]
 		}
 
-		err = parseExecArgs(cc.ctx.GetSessionVars().StmtCtx, args, stmt.BoundParams(), nullBitmaps, stmt.GetParamsType(), paramValues)
+		err = parseExecArgs(cc.ctx.GetSessionVars().StmtCtx, args, stmt.BoundParams(), nullBitmaps, stmt.GetParamsType(), paramValues, cc.inputDecoder)
 		stmt.Reset()
 		if err != nil {
 			return errors.Annotate(err, cc.preparedStmt2String(stmtID))
@@ -310,7 +313,8 @@ func parseStmtFetchCmd(data []byte) (uint32, uint32, error) {
 	return stmtID, fetchSize, nil
 }
 
-func parseExecArgs(sc *stmtctx.StatementContext, args []types.Datum, boundParams [][]byte, nullBitmap, paramTypes, paramValues []byte) (err error) {
+func parseExecArgs(sc *stmtctx.StatementContext, args []types.Datum, boundParams [][]byte,
+	nullBitmap, paramTypes, paramValues []byte, enc *inputDecoder) (err error) {
 	pos := 0
 	var (
 		tmp    interface{}
@@ -318,6 +322,9 @@ func parseExecArgs(sc *stmtctx.StatementContext, args []types.Datum, boundParams
 		n      int
 		isNull bool
 	)
+	if enc == nil {
+		enc = newInputDecoder(charset.CharsetUTF8)
+	}
 
 	for i := 0; i < len(args); i++ {
 		// if params had received via ComStmtSendLongData, use them directly.
@@ -543,6 +550,7 @@ func parseExecArgs(sc *stmtctx.StatementContext, args []types.Datum, boundParams
 			}
 
 			if !isNull {
+				v = enc.decodeInput(v)
 				tmp = string(hack.String(v))
 			} else {
 				tmp = nil

server/conn_stmt_test.go

@@ -197,12 +197,25 @@ func TestParseExecArgs(t *testing.T) {
 		},
 	}
 	for _, tt := range tests {
-		err := parseExecArgs(&stmtctx.StatementContext{}, tt.args.args, tt.args.boundParams, tt.args.nullBitmap, tt.args.paramTypes, tt.args.paramValues)
+		err := parseExecArgs(&stmtctx.StatementContext{}, tt.args.args, tt.args.boundParams, tt.args.nullBitmap, tt.args.paramTypes, tt.args.paramValues, nil)
 		require.Truef(t, terror.ErrorEqual(err, tt.err), "err %v", err)
 		require.Equal(t, tt.expect, tt.args.args[0].GetValue())
 	}
 }
 
+func TestParseExecArgsAndEncode(t *testing.T) {
+	dt := make([]types.Datum, 1)
+	err := parseExecArgs(&stmtctx.StatementContext{},
+		dt,
+		[][]byte{nil},
+		[]byte{0x0},
+		[]byte{mysql.TypeVarchar, 0},
+		[]byte{4, 178, 226, 202, 212},
+		newInputDecoder("gbk"))
+	require.NoError(t, err)
+	require.Equal(t, "测试", dt[0].GetValue())
+}
+
 func TestParseStmtFetchCmd(t *testing.T) {
 	tests := []struct {
 		arg       []byte

server/util.go

@@ -290,6 +290,32 @@ func dumpBinaryRow(buffer []byte, columns []*ColumnInfo, row chunk.Row, d *resul
 	return buffer, nil
 }
 
+type inputDecoder struct {
+	encoding *charset.Encoding
+
+	buffer []byte
+}
+
+func newInputDecoder(chs string) *inputDecoder {
+	return &inputDecoder{
+		encoding: charset.NewEncoding(chs),
+		buffer:   nil,
+	}
+}
+
+// clean prevents the inputDecoder from holding too much memory.
+func (i *inputDecoder) clean() {
+	i.buffer = nil
+}
+
+func (i *inputDecoder) decodeInput(src []byte) []byte {
+	result, err := i.encoding.Decode(i.buffer, src)
+	if err != nil {
+		return src
+	}
+	return result
+}
+
 type resultEncoder struct {
 	// chsName and encoding are unchanged after the initialization from
 	// session variable @@character_set_results.