tables: make duplicate error in update clearer

executor/insert_test.go

@@ -97,6 +97,18 @@ func (s *testSuite) TestInsertOnDuplicateKey(c *C) {
 	tk.MustQuery(`select * from t;`).Check(testkit.Rows(`1 2 3`))
 }
 
+func (s *testSuite) TestUpdateDuplicateKey(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+
+	tk.MustExec(`drop table if exists t;`)
+	tk.MustExec(`create table c(i int,j int,k int,primary key(i,j,k));`)
+	tk.MustExec(`insert into c values(1,2,3);`)
+	tk.MustExec(`insert into c values(1,2,4);`)
+	_, err := tk.Exec(`update c set i=1,j=2,k=4 where i=1 and j=2 and k=3;`)
+	c.Assert(err.Error(), Equals, "[kv:1062]Duplicate entry '1-2-4' for key 'PRIMARY'")
+}
+
 func (s *testSuite) TestInsertWrongValueForField(c *C) {
 	tk := testkit.NewTestKit(c, s.store)
 	tk.MustExec("use test")

executor/write_test.go

@@ -1000,7 +1000,7 @@ func (s *testSuite) TestUpdate(c *C) {
 	_, err = tk.Exec("update ignore t set a = 1 where a = 2;")
 	c.Assert(err, IsNil)
 	r = tk.MustQuery("SHOW WARNINGS;")
-	r.Check(testkit.Rows("Warning 1062 key already exist"))
+	r.Check(testkit.Rows("Warning 1062 Duplicate entry '1' for key 'I_uniq'"))
 	tk.MustQuery("select * from t").Check(testkit.Rows("1", "2"))
 
 	tk.MustExec("drop table if exists t")

table/tables/tables.go

@@ -748,6 +748,16 @@ func (t *tableCommon) removeRowIndex(sc *stmtctx.StatementContext, rm kv.Retriev
 // buildIndexForRow implements table.Table BuildIndexForRow interface.
 func (t *tableCommon) buildIndexForRow(ctx sessionctx.Context, rm kv.RetrieverMutator, h int64, vals []types.Datum, idx table.Index) error {
 	if _, err := idx.Create(ctx, rm, vals, h); err != nil {
+		if kv.ErrKeyExists.Equal(err) {
+			// Make error message consistent with MySQL.
+			entryKey, err1 := t.genIndexKeyStr(vals)
+			if err1 != nil {
+				// if genIndexKeyStr failed, return the original error.
+				return errors.Trace(err)
+			}
+
+			return kv.ErrKeyExists.FastGen("Duplicate entry '%s' for key '%s'", entryKey, idx.Meta().Name)
+		}
 		return errors.Trace(err)
 	}
 	return nil